• Magazine of the Korean Society of Agricultural Engineers
• /
• v.32 no.3
• /
• pp.87-101
• /
• 1990

The purpose of this study is to estimate the flood discharge and runoff volume at a stream by using geomorphologic parameters obtained from the topographic maps following the law of stream classification and ordering by Horton and Strahier. The present model is modified from Cheng' s model which derives the geomorphologic instantaneous unit hydrograph. The present model uses the results of Laplace transformation and convolution intergral of probability density function of the travel time at each state. The stream flow velocity parameters are determined as a function of the rainfall intensity, and the effective rainfall is calculated by the SCS method. The total direct runoff volume until the time to peak is estimated by assuming a triangular hydrograph. The model is used to estimate the time to peak, the flood discharge, and the direct runoff at Andong, Imha. Geomchon, and Sunsan basin in the Nakdong River system. The results of the model application are as follows : 1.For each basin, as the rainfall intensity doubles form 1 mm/h to 2 mm/h with the same rainfall duration of 1 hour, the hydrographs show that the runoff volume doubles while the duration of the base flow and the time to peak are the same. This aggrees with the theory of the unit hydrograph. 2.Comparisions of the model predicted and observed values show that small relative errors of 0.44-7.4% of the flood discharge, and 1 hour difference in time to peak except the Geomchon basin which shows 10.32% and 2 hours respectively. 3.When the rainfall intensity is small, the error of flood discharge estimated by using this model is relatively large. The reason of this might be because of introducing the flood velocity concept in the stream flow velocity. 4.Total direct runoff volume until the time to peak estimated by using this model has small relative error comparing with the observed data. 5.The sensitivity analysis of velocity parameters to flood discharge shows that the flood discharge is sensitive to the velocity coefficient while it is insensitive to the ratio of arrival time of moving portion to that of storage portion of a stream and to the ratio of arrival time of stream to that of overland flow.

• Journal of Environmental Science International
• /
• v.22 no.9
• /
• pp.1079-1088
• /
• 2013

The objective of this paper is compare to landuse type for calculating peak flood and soil loss in rapidly expansion urban area. This study compares two landuse maps, including numerical landuse map and aerial photograph landuse map, for calculating the ratio of urban and agriculural area, curve number, time of concentration, peak flood discharge, and soil loss. It is found that flood discharge calculated using aerial photograph landuse map are larger than that calculated using numerical landuse map, and soil loss calculated using aerial photograph landuse map are smaller than that calculated using numerical landuse map. Results also indicate that landuse chage in rapidly expansion urban area significantly influences flood discharge and soil loss.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.4
• /
• pp.47-55
• /
• 1998

A new ignition system concept was developed to improve ignition performance, accuracy of control and the reliability of the ignition system. The new ignition system has ho호 frequency discharge characteristics with 1.5-2.0 ms discharge duration, in place of the usual solitary longer duration event. We applied the system to a commercial engine to study its influence on the maximum combustion pressure attained during the cycle, when this peak pressure occurred, imep, variation rate of the engine speed and the flammability limit of a lean mixture. In this study, we clarified that the new ignition system had a beneficial effect of the lean mixture flammability limit. Also for a given mixture strength we found that the mew ignition system gave a higher peak cylinder pressure than in the case of the conventional ignition system.

• Korean Journal of Materials Research
• /
• v.12 no.6
• /
• pp.447-451
• /
• 2002

Pulsed DC-plasma nitriding has been applied to form nitride layer having only a diffusion layer. The discharge current with the variation of discharge gases is proportional to the intensity of $N_2^+$ peak in optical emission spectroscopy during the plasma nitriding. The discharge current, microhardness in surface of substrate and depth of nitride layer increased with the ratio of $N_2\;to\;H_2$ gas in discharge gases. When the ratio of $N_2\;to\;H_2$ is lower than 60% in the discharge gases, high microhardness value of 1100Hv nitride layer which contains no compound layer has been formed.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.6 no.4 s.23
• /
• pp.37-47
• /
• 2006

Urban development results in increased runoff volume and flowrates and shortening in time of concentration, which may cause frequent flooding downstream. Flow retardation structures to limit adverse downstream effects of urban storm runoff are used. There are various types of flow retardation measures include detention basins, retention basins, and infiltration basins. In basic planning phase, a number of planning models of detention ponds which decide storage volume by putting main variables were used to design detention ponds. The characteristics of hydrological parameters $\alpha,\;\gamma$ which are used in planning models of detention pond were analyzed. In this study, detention ponds data of Disaster Impact Assessment report at 22 sites were analyzed in order to investigate correlation between characteristic of urban drainage basin parameter and characteristics of detention pond parameter due to urbanization effects. The results showed that storage volume was influenced by peak discharge ratio $\alpha$ more than runoff coefficient ratio $\beta$ and peak discharge ratio $\alpha$ was influenced by runoff coefficient ratio $\beta$ less than regional parameter n. Storage ratio was mainly influenced by duration of design rainfall in the case of trapezoidal inflow hydrograph such as Donahue et al. method.

• Current Research on Agriculture and Life Sciences
• /
• v.7
• /
• pp.55-66
• /
• 1989

The purpose of this study is to estimate the flood discharge and peak time by the SCS method and the probability method using the geomorpologic parameters obtained from the topographic maps following the law of stream classifying and, ordering by Horton and Strahler. The SCS method and the probability method are used in estimating the times to peak and the flood discharges at An-dong, Im-ha, and Sun-san basins in the Nakdong River system. The results obtained are as follows : 1. The range of the values of the area ratio, the bifurcation ratio and the length ratio agree with those of natural streams presented by Horton and Strahler. 2. Comparisons of the probability method and observed values show that small relative errors of 0-7% of flood discharge, and 0-2hr, difference in time to peak respectivly. But the SCS method shows that large relative errors of 10-40% of flood discharge, and 0-4hr, difference in time to peak. 3. When the rainfall intensity is large, the error of flood discharge estimated by using the probability method is relativly small.

• Journal of Digital Convergence
• /
• v.17 no.7
• /
• pp.131-138
• /
• 2019

The world's electricity production ratio is 40% for coal, 20% for natural gas, 16% for hydroelectric power, 15% for nuclear power and 6% for petroleum. Fossil fuels also cause serious problems in terms of price and supply because of the high concentration of resources on the earth. Solar energy is attracting attention as a next-generation eco-friendly energy that will replace fossil fuels with these problems. In this study, we test the charge-operation plan and the discharge operation plan for peak-cut operation by applying the maximum power demand reduction simulation. To do this, we selected the electricity usage from November to February, which has the largest amount of power usage, and applied charge / discharge logic. Simulation results show that the contract power decreases as the peak demand power after the ESS Peak-cut service is reduced to 50% of the peak-target power. As a result, the contract power reduction can reduce the basic power value of the customer and not only the economic superiority can be expected, but also contribute to the improvement of the electric quality and stabilization of the power supply system.

• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.7
• /
• pp.167-175
• /
• 1996

Work roll wear in the cold rolling of steel strip is strongly affected by rolling materials, rolling conditions and lubrication. Tests were performed to find the effects of rolling materials under the same lubricating conditions. Surface roughness of cold rolled steel strip as well as the coating technique itself is quite improtant in obtaining high image clarity of electronic products and car outer panels. Therefore this paper reviews for improvement of roughness and peak count about the surface of Cr coated work roll is investigated from the actual temper mill. The conclusions were obtained as follows; 1) Work roll wear in the cold rolling of steel strip is strongly affected by carbon contents of rolling materials, but there is not a separating force and total reduction ratio. 2) The roughness of strip surface is larger in the direction of width than in roll direction. 3) The electro-discharge textured roll has more uniform roughness distribu- tion than shot blasted roll and it's life time is two times longer than shot blasted because it has more harmonic wave roughness, and the higher peak count of surface roughness. 4) The life time of Cr coated work roll is 2 times longer than that of shot blasted work roll and variation of peak count, roughness and life time of Cr coated work roll is similar to electro-discharge texturing work roll. 5) The proper Cr coating thickness is 10 .mu. m at the work roll of temper mill.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.518-521
• /
• 1999

This paper describes the properties of discharge current and the residual voltage for $^{60}$ C$_{0}$ -${\gamma}$ irradiated cables using in nuclear power generating station. As these properties related with $^{60}$ C$_{0}$ -${\gamma}$ -irradiatiation dose, it is suggested that these properties can be utilized as a index of irradiation degradation. As the ratio of degradation increases, the residual voltage in the initial time range increases and the peak moves to the shorter time. Therefore, I know the degree of radiation degradation from the position of the peak.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.279-282
• /
• 1997

The propose of this study is research and improvement of LiNiO$_2$as cathode material for Lithium secondary batteries. LiNiO$_2$is prepared by heating LiOH . $H_2O$ and Ni(OH)$_2$(mole ratio 1 : 1) on various heat condition. In the result of XRD mesurement, all LiNiO$_2$prepared at this study showed hexagonal structure. In Cyclic Voltammetry, LiNiO$_2$is not conspicous about oxidation peak but oxidation curve change steeply over 3.8V and reduction peak discover at 3.6V. In discharge capacities, specific capacity is higher $O_2$than air when preliminary heated and 75$0^{\circ}C$ than $700^{\circ}C$, 80$0^{\circ}C$ when heated. Therefore, when preliminary heat at $650^{\circ}C$ $O_2$and heat at 75$0^{\circ}C$ carried out, discharge property is the best.