• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.5
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• pp.58-64
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• 2000

This paper proposes a method for determining optimal EDM parameters based on discharge area from the physical model of a tool electrode. Main parameters, which affect the EDM performance, are peak value of currents, pulse-on time, and pulse-off time. Such parameters are closely dependent on the discharge area in EDM process. In this paper the discharge area is estimated from the CMM scanning data to the tool electrode. The method is very useful when any geometric information to the tool electrode is not provided from tool modeler or producer. The method consists of following four steps. First a triangulation mesh is constructed from the CMM data. Secondly, the z-map is modeled from the triangulated mesh. Thirdly, the discharge area is estimated from intersection between the z-map model and a z-height plane. Finally, the machining parameters are easily calculated by some known EDM equations to the discharge area. An example is introduced to show that the machining parameters are calculated from the CMM data to a tool electrode.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.44-51
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• 2004

In a micro-EDM, it is well known that an RC circuit is suitable as a discharge circuit because of its low pulse width and relatively high peak current. To increase machining speed without changing unit discharge energy, charge resistance should be decreased. But, when the resistance is very low, continuous (or normal) arc discharge occurs, electrode wear increases and machining speed is reduced remarkably. In this paper, an RC circuit with transistors is used in a micro-EDM. Experimental results show that the RC circuit with transistors can cut off a continuous (o. normal) arc discharge effectively if the duty factor and switching period of the transistor are set up optimally. Through experiments with varying charge resistances, it is shown that the RC circuit with transistors has about two times faster machining speed than that of an RC circuit.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.296-299
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• 2005

Time series of spring discharge data in Jeju island can provide abundant information on the spatial groundwater system. In this study, the classification based on time series of spring discharge was performed with clustering analysis: discharge rate and EC. Peak discharges are mainly observed in august or september. However, double peaks and late peaks of discharge are also observed at a plenty of springs. Based on results of clustering analysis, it can be deduced that GH model is not appropriate for the conceptual model of Groundwater system in Jeju island. EC distributions in dry season are also support the conclusion.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.997-1004
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• 2011

A fault detection algorithm of a charge and discharge system to ensure the safe use of hybrid electric vehicle is proposed in this paper. This algorithm can be used as a complementary way to existing fault detection technique for a charge and discharge system. The proposed algorithm uses a SVDD technique, which additionally utilizes two methods for learning a large amount of data; one is to incrementally learn a large amount of data, the other one is to remove the data that does not affect the next learning using a new data reduction technique. Removal of data is selected by using lines connecting support vectors. In the proposed method, the data processing speed is drastically improved and the storage space used is remarkably reduced than the conventional methods using the SVDD technique only. A battery data and speed data of a commercial hybrid electrical vehicle are utilized in this study. A fault boundary is produced via SVDD techniques using the input and output in normal operation of the system without using mathematical modeling. A fault detection simulation is performed using both an artificial fault data and the obtained fault boundary via SVDD techniques. In the fault detection simulation, fault detection time via proposed algorithm is compared with that of the peak-peak method. Also the proposed algorithm is revealed to detect fault in the region where conventional peak-peak method is never able to do.

• Journal of Korea Water Resources Association
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• v.48 no.3
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• pp.209-220
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• 2015

In this study, the effects of changed environment on spatial extension of flood discharge data which is generating discharge data at ungauged watersheds. Especially, effects of dams on spatial extensions of flood discharge data and on natural flow generation were studied. This is somehow an intial trial of flood discharge data generation for heterogeneous watersheds because of dam installation. Data extensions have been performed based on the flood discharge data from YeoJoo water gauge station located on the Nam-Han River. For the evaluation of flood discharge data spatial extension under dam effects and producing natural flow, 41 flood events associated with YeoJoo water gauge station were selected from 1986 to 2010. When flood discharge data were extended based on YeoJoo water gauge station, 77% of selected flood events were over the satisfaction ranges (NSE>0.5) of Nash-Sutcliffe Efficiency for model validation. Extended flood discharge data at Yangpyung has 0.84 NSE obtained from spatial data extension based on YeoJoo water gauge station. Generated natural flow at YeoJoo was influenced strongly by Chungju Dam which has larger effects on streamflow at YeoJoo than Hoangsung Dam. Observed peak discharges after the 1986 of Chungju Dam installation were smaller than those of the obtained natural flow. Through these results, spatial extension of flood discharge data with installed dams works efficiently for ungauged watersheds and natural flow can be generated using extended flood discharge data.

• Korean Journal of Ecology and Environment
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• v.43 no.4
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• pp.471-476
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• 2010

Monthly up-river discharge in the riverine zone analysis resulted in large interannual variations and differences in calcium ($Ca^{2+}$), bicarbonate ($HCO_3^-$), and cations in the lacustrine zone (Lz) of Daecheong Reservoir during the wet year (Wy, 1993) vs. dry year (Dy, 1994). Total up-river discharge in the Wy was four times that of the Dy, and the up-river discharge in July~August of the Wy was eight times greater than that of same period of Dy. Annual water retention time in the Lz showed large difference between the two years. Water residence time (WRT) was minimum when the up-river discharge peaked, whereas the WRT was maximum when the up-river discharge was at minimal condition. This peak discharge from the up-river on early July reduced residence time in the Lz on mid-July~late July. Monthly pattern, based on data of May~November, was similar between the two years, but, but mean retention time in the Wy was 50 days shorter than in the Dy. Such hydrology, up-river discharge, and WRT reduced $Ca^{2+}$, $HCO_3^-$, and cations in the Lz. At low up-river discharge in Wy during April~May, the cation content of Ca+Mg+Na+K averaged 1.17meq $L^{-1}$ (range=1.09-1.26meq $L^{-1}$), but as the up-river discharge increased suddenly, the values decreased. Seasonal fluctuations of $Ca^{2+}$ showed exactly same pattern with bicarbonate ion of $HCO_3^-$. The minimum $Ca^{2+}$ (0.03meq $L^{-1}$) was occurred in the early August of wet year and coincided with the minimum $HCO_3^-$. These results suggest that the magnitude of variation in $Ca^{2+}$, bicarbonate, and cations in the lacustrine zone is directly determined by the peak magnitude of up-river discharge. The magnitude of up-river discharge determined water retention time and the magnitude of ionic dilution in the lacustrine zone, resulting in functional changes of the ecosystem.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.2
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• pp.134-142
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• 1997

This study was performed to evaluate the drain runoff characteristics from one paddy field, and to provide the basic data required for the determination of flood discharge and unit drainage water for drainage improvement and farmland consolidation. For this purpose, under the assumption that drain discharge from paddy field was similar to outflow of reservoir, runoff model based on storage equation was applied to the experimental field, and simulated results were compared to the measured discharge at weir point. To estimate effective storage volume of paddy field with water depth, 4 regression formula were examined such as linear, exponential, power, and combined. From the observed runoff characteristics, it was shown to be 3.3~16.3${\ell}$/sec in weir discharge, 57.2~98% in runoff ratio, and relative error of simulated result was 3.0~39.4%, 8.5 ~56.0 % for peak flow and runoff ratio, respectively. Curve number by SCS method was calculated as mean value of 96.4 using measured rainfall and runoff data, it was considered relatively high because paddy field has generally flooding depth contrary to the upland watershed area.

• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.100-105
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• 2000

Correlation between propagation of bush-type electrical tree and internal partial discharges(PD) was discussed. We used specimens with needle-plane electrode system made of LDPE(Low Density Polyethylene), observed inception and propagation of electrical tree by optical microscope interfaced with computer and investigated characteristics of phase resolved PD pulses accompanying with propagation of electrical tree. Electrical tree generally growed bush-type tree. PD data detected and analyzed were average discharge current and statistical operator of q-n, $\psi$- $q_{avg}$, $\psi$-n, ${\psi}-q_{max}$ distribution. Parameters used were skewness, kurtosis, average discharge phase, cross-correlation factor, asymmetry and etc. In generally, average discharge current had good linear relationship with propagation of bush type electrical tree on this experiment. Peak discharge magnitude and repetition rate were increased, but they had not good linear relationship.p.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.539-540
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• 2002

A self-discharge in multi-EEFLs and CCFLs has been found to provide a high luminance and efficiency. With a fast rising and falling times of $2{mu}s$, and the peak voltage over 1.6KV, the self-discharge occurs in EEFLs and CCFLs driven by a full bridge switching inverter. Particularly in CCFLs connected with a typical value of ballast capacitance, a self-discharge follows by the main discharge when the voltage falls to the ground.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.1
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• pp.22-28
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• 1996

From the experimental study of Wire-Cut Electric Discharge Machining of STD-11 alloy steel and P-20 tungsten carbide, the characteristics such as hand drum form and discharge gap have been observed and evaluated for various conditions. Hand drum form can be improved when gap have been observed and evaluated for various conditions. Hand drum form can be improved when gap voltage and spark cycle become smaller, thickness become thinner, wire tension become larger and the no of cutting increases. When 60mm thickness tungsten carbide is cut in normal condition, hand drum form becomes larger due to the low conductivity machining allowance become slightly larger when peak discharge current and gap voltage become larger, or wire tension becomes smaller. Under the same condition, machining allowance of tungsten carbide is larger than alloyed steel by 1/100mm.