• 한국정밀공학회지
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• 제14권5호
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• pp.53-59
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• 1997

This study has been performed to inmvestigate MRR(metal removal rate), REW(relative electrode wear), surface roughness, heat transumutation layer and microhardness distribution in cross-section of the machined surface with various pulse-on duration and peak pulse current, using the copper and graphite electrode on the heat treated STD11 which is extensively used for metallic molding steel with the EDM. The results obtained are as follows; a) There exists critical pulse-on duration(If Ip equals 5A, .tau. on is 50 .mu. s) which shows the the maximum MRR in accordance with peak oulse current and the MRR decreases when the pulse-on duration exceeds the critical pulse-on during because of the abnormal electric discharge. b) Safe discharge is needed to make maximum of MRR and the metalic organization must be complicated for discharge induction. c) Graphite has much more benefits than copper electrode when rapid machining is done without electrode wear. d) The most external surface has the highest microhardness because of car- burizing from heat analysis of the dielectric fluid and the lower layar of the white covered layer has lower microhar dness than base matal because of softening.

• 한국안전학회지
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• 제16권4호
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• pp.7-13
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• 2001

Wire electrical discharge machining experiments in conducted to investigate characteristics of acoustic emission (AE) and electrical discharge energy due to current peak (I$_{p}$), pulse on time($\tau$/on/). The AE signals are obtained with a sensor attached to workpiece side. Machining states are identified with scanning electron microscopy and residual stress analyzer. It is demonstrated that the residual stress provide reliable informations about the machining states. Moreover, machining states can be detected successfully using both the residual stress and AE count rate.e.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.315-316
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• 2002

Electrochemical discharge machining is a very recent technique for non-conducting materials such as ceramics and glasses. ECDM is conducted in the NaOH solution and the cathode electrode is separated from the solution by $H_2$ gas bubble. Then the discharge is appeared and the non-conductive material is removed by spark and some chemical reactions. In the ECDM technology, the $H_2$ bubble control is the most important factor to stabilize the discharging condition. In this paper, we proposed the discharge peak monitoring/ discharging duty feedback algorithms for the discharge stabilization and the feasibility of this algorithm is verified by various pattern machining in the constant preload conditions for the cathode electrode.

• KSTLE International Journal
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• 제3권2호
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• pp.95-100
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• 2002

Electrochemical discharge machining is a very recent technique for non-conducting materials such as ceramics and glasses. ECDM is conducted in the NaOH solution and the cathode electrode is separated from the solution by H$_2$ gas bubble. Then the discharge is appeared and the non-conductive material is removed by spark and some chemical reactions. In the ECDM technology, the H$_2$ bubble control is the most important factor to stabilize the discharging condition. In this paper we proposed the discharge peak monitoring/discharging duty feedback algorithms fur the discharge stabilization and the feasibility of this algorithm is verified by various pattern machining in the constant preload conditions for the cathode electrode.

• 물과 미래
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• 제26권2호
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• pp.49-57
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• 1993

본 연구는 하수관거 설계시, 계획강우의 임계지속기간을 결정하기 위한 것으로서, 지속기간내의 시간적 강우분포형은 Huff의 4분위법에 의하였으며, 20분~240분의 9개의 지속기간을 10년 빈도강우에 대하여 검토하였다. 본 연구에서는 서울시 관내의 18개 유수지 배수구역을 대상으로 해석을 시도하였으며, 유출해석을 위하여 ILLUDAS 모형을 이용하였다. 하수관거의 설계수문량 기준이 되는 첨두유출량을 최대로 발생시키는 계획강우의 임계지속기간은 대체로 30,60분으로 판단되었다. 계획강우의 시간적 분포형별로 임계지속기간을 설정할 수 있도록 첨두유량-유역면적-임계지속기간의 관계도를 제시하였다.

• Korean Journal of Hydrosciences
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• 제5권
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• pp.17-31
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• 1994

Because of the Keumkangsan-Dam and the Peace-Dam constructed in recent years, it is expected that the peak flood discharge and the peak flood stage at the Hwachun-Dam site have been changed. In this study, two methods were used to simulate and compare the effects of the upstream dam construction on the change of the discharge and the stage. One is the storage function method widely used for the hydrological routing in the country. The other is the DWOPER(Dynamic Wave Operational Model) package conducted on four different scenarios: (1) before the construction of the Keumkangsan-Dam and the Peace-Dam; (2) the exclusion of the Keumkangsan-Dam watershed (before the construction of the Peace-Dam); (3) the exclusion of the Keumkangsan-Dam watershed (after the construction of the Peace-Dam) ; (4) the exclusion of the Peace-Dam watershed. The results of the four test cases from the two methods show that the peak flood discharge and the peak flood stage at the Hwachun-Dam site are reduced due to the construction of the Peace-Dam. From these findings, it is suggested that the operational criteria for the optimal dam-operation of the Hwachun-Dam need to be modified.

• 한국습지학회지
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• 제19권3호
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• pp.335-344
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• 2017

본 연구에서는 미계측유역의 설계홍수량을 산정하는 방안으로 유역의 면적비를 적용하는 방안을 제안하였다. 이를 위해 유역출구에서의 실측자료를 활용하여 유출매개변수를 결정하고 면적비를 적용하여 첨두홍수량을 산정하였다. 위 방법론을 검증하기 위해 소하천 유역의 관측유량 및 하천정비종합계획의 설계홍수량과의 비교를 통해 면적비 전이 방법론의 타당성을 검토하였다. 그 결과를 정리하면 다음과 같다. 면적비를 적용한 유출량과 관측유량자료를 비교한 결과 14~25% 정도의 차이를 보였다. 제안된 방법론의 타당성을 재확인하기 위해 하천정비종합계획에서 산정된 첨두유량과 소유역과의 면적비로 계산한 첨두유량을 비교하였다. 이를 위해 31개소의 소하천을 대상으로 설계홍수량을 비교한 결과, 20% 정도의 홍수량의 차이가 발생하였다. 따라서 면적비를 적용한 미계측지역에서의 첨두유량 산정방법론이 타당하다고 판단된다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1666-1670
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• 2006

The purpose of this study is to analyze how a downstream channel is affected in case of hypothetical dam failure. The object of it is Hwacheon dam basin within the basin of North Han river. This study has analyzed the influence on Pyeonghwa(Peace) dam and Hwacheon dam supposing that the Imnam dam in North Korea on the upper stream of North Han river is failed hypothetically at the MFWL(maximum flood water level) by a deluge of rain. The model applied at the main study is NWS(National Weather Service) FLDWAV(Flood Wave Routing Model). Dam breach characteristics data are analyzed by making nine hypothetical scenarios on the basis of other studies on the shape and size of dam breach, time of failure and so on. Expected peak discharge through the breach is verified to have the propriety in comparison with empirical function which is developed on the basis of the case of dam breach in the foreign countries and it is observed that peak discharge is more increasing, as the time of breach gets shorter and the breach width gets bigger. As a result of main study, even though the Imnam dam is hypothetically failed down, there has no influence on the Hwacheon dam of the downstream as the extended Pyeonghwa dam on the downstream controls the volume of discharge properly.

• 전기학회논문지
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• 제58권9호
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• pp.1784-1789
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• 2009

This paper describes the measurement technology of the dissolved hydrogen gas due to partial discharge in oil using gas sensor. For higher resolution and less error in measurement of the dissolved hydrogen gas in oil, the sensor outputs with ambient temperature which affect the sensor output characteristics should be considered. The sensor output trends with ambient temperature and the properties of the dissolved hydrogen gas in oil with partial discharge characteristic were analyzed through the test results. It was indicated that the sensor peak and the base voltage with measuring time were affected by ambient temperature and the measurement errors of the sensor output by temperature were reduced by using the difference between the peak and the base voltage rather than just the peak voltage. In addition, the hydrogen gas sensor outputs were increased with the increase of partial discharge energy.

• 한국정밀공학회지
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• 제12권5호
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• pp.69-76
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• 1995

This paper describes characteristics of EDT(Electro Discharge Texturing) and that the strip surface has influence on the paintability. The pulse mode and the capacitor mode of recently developed EDT method were investigated about the peak shape and the roughness of strip surface. And EDT method compared the above-mentioned contents with the SBT(Shot Blast Texturing) method. The peak count of the pulse mode is more than that of the capacitor mode. But the lower roughness below the Ra 3.2 .mu. m of the strip surface, the texturing time of the pulse mode is longer than the capacitor mode. In SBT method, the peak shape is similar to capacitor mode. But the EDT roll has more uniformity than the SBT roll and has more peak count than that of SBT roll. Therefore, in the painted steel sheet, EDT roll gives better surface of clarity image than the SBT roll.