• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.25-32
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• 1997

The neural network was applied to identify wear debris generated from the lubricated machine moving surface. The wear test was carried out under different experimental conditions. In order to describe characteristics of debris of various shapes and sizes. The four parameter(50% volumetric diameter, aspect, roundness and reflec- tivity) of wear debris are used as inputs to the network and learned the friction condition of five values (material 3, applied load 1, sliding distance 1). It is shown that identification results depend on the ranges of these shape parameter learned. The three kinds of the wear debris had a different pattern characteristic and recognized the friction condition and materials very well by neural network.

• 한국정밀공학회지
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• 제27권10호
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• pp.45-51
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• 2010

Electrical discharge drilling (ED-drilling) is a widespread machining method used to bore small holes with a high aspect ratio. This paper presents additional methods by which ED-drilling can improve machining speed, tool wear, and machined surface quality. Firstly, for high machining speed, and low tool wear, a new-type electrode that was ground on one side or both sides of the cylindrical electrodes was suggested to expel debris. The debris which is generated during the machining process can cause sludge deposition and secondary discharge problems: major reasons to decrease machining speed. This new-type electrode also reduced tool wear that was due to the decrease of unstable discharge in a machining gap by helping to expel waste water and debris from the gap. Secondly, to improve the machined surface roughness, an electrolyzation process was included after drilling. This process made the machined surface smooth by means of an electrochemical reaction between an electrode and a workpiece. In this study, the machining speed, electrode wear, and surface roughness were improved by the newtype electrode and the electrolytic process.

• 반도체디스플레이기술학회지
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• 제5권3호
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• pp.5-10
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• 2006

This paper investigates cutting qualities after laser dicing and predicts the problems that can be generated by laser dicing. And through 3 point bending test, die strength is measured and the die strength after laser dicing is compared with the die strength after mechanical sawing. Laser dicing is chiefly considered as an alternative to overcome the defects of mechanical sawing such as chipping on the surface and crack on the back side. Laser micromachining is based on the thermal ablation and evaporation mechanism. As a result of laser dicing experiments, debris on the surface of wafer is observed. To eliminate the debris and protect the surface, an experiment is done using a water soluble coating material and ultrasonic. The consequence is that most of debris is removed. But there are some residues around the cutting line. Unlike mechanical sawing, chipping on the surface and crack on the back side is not observed. The cross section of cutting line by laser dicing is rough as compared with that by mechanical sawing. But micro crack can not be seen. Micro crack reduces die strength. To measure this, 3 point bending test is done. The die strength after laser dicing decreases to a half of the die strength after mechanical sawing. This means that die cracking during package assembly can occur.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2420-2427
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• 2000

In contacting between surface, there is wear and the generation of wear particles. The particles contained in the lubricating oil carry detailed and important information about the condition monitoring of the machine. Therefore, This paper was undertaken for Ferrography system of wear debris generated from lubricated moving machine surface. The lubricating wear test was performed under different experimental conditions using the Falex wear test of Pin and V-Block type by Ti(C,N) coated. It was shown from the test results that wear particle concentration(WPC) ; wear severity Index(IS) and size\distribution have come out all the higher value by increases sliding friction time. By the Ferrogram a thin leaf wear debris as well as ball and plate type wear particles was observed.

• 한국해양환경ㆍ에너지학회지
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• 제15권2호
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• pp.89-100
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• 2012

본 연구는 서해안 일대의 국가 해양쓰레기 모니터링 구역을 대상으로 외국기인 해양쓰레기의 발생 특성과 해양 환경의 변화에 따른 시기별 변화를 파악하고자 하였다. 서해안으로 유입되는 외국 기인 해양쓰레기는 제주 차귀도(5,112개)가 가장 많았으며, 다음은 진도 하조도(1,967개), 신안 임자도(507개) 순으로 조사되었다. 대부분 부유성이 높은 플라스틱 제품으로 플라스틱 음료수병(2,925개)이 가장 많은 양을 차지하였다. 시기별 발생량은 주로 7월, 9월에 집중되었으며, 이 시기의 해양 환경을 분석한 결과, 해상풍의 주풍향은 남풍 또는 남동풍 계열이 지배적이었다. 해수 표층 흐름의 경우 중국 연안을 따라 남하하는 해수의 흐름과 동중국해로부터 북상하는 해수 흐름의 유입이 우세하게 나타났다.

• 한국정밀공학회지
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• 제20권12호
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• pp.191-197
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• 2003

As mechanical components are miniaturized, the demand on micro die and mold is increasing. Micro mechanical components usually have high hardness and good conductivity. So micro electrical discharge machining (MEDM) is an effective way to machine those components. In micro cavity fabrication using MEDM, it is observed that the bottom surface of cavity is distorted. Electric charges tend to be concentrated at the sharp edge. At the center of the bottom surface, debris can not be drawn off easily. These two phenomena make the bottom surface of the electrode and workpiece distort. As machining depth increases, the distorted shape of electrode approaches hemisphere. This process is affected by capacitance and the size of electrode. By using a smaller electrode than the desired cavity size and appropriate tool movement, bottom shape distortion can be prevented.

• International Journal of Precision Engineering and Manufacturing
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• 제6권4호
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• pp.44-48
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• 2005

As mechanical components are miniaturized, the demands on micro die/mold are increasing. Micro mechanical components usually have high hardness and good conductivity. Micro electrical discharge machining (MEDM) can thus be an effective way to machine those components. In micro cavity fabrication using MEDM, it is observed that the bottom surface of the cavity is distorted. Electric charges tend to be concentrated at the sharp edge, and debris cannot be drawn off easily at the center of the bottom surface. These two phenomena make the bottom surface of electrode and workpiece distort. As machining depth increases, the distorted shape of the electrode approaches hemisphere. This process is affected by both capacitance and the size of electrode. By using a smaller electrode than the desired cavity size and appropriate tool movement, bottom shape distortion can be prevented.

• 한국지형학회지
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• 제28권3호
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• pp.13-26
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• 2021

In mountain gully, channelized debris flow is an important phenomenon in the process of topographical change. Social infrastructure as roads may be damaged by channelized debris flows, but there has been little information about their occurrence and movement to prepare for the risk of the debris flow. Most of the channelized debris flows occur during heavy rains in mountainous valleys that are difficult to access, so there are not many field data. In this study, the topographical characteristics of the catchment, the rainfall and runoff related to the debris flow, the sedimentary pattern and the cross-sectional change of the channel bed, and the underflow velocity of the gravel bed have been investigated and analyzed in the Singi gully where the channelized debris flows occurred. In the catchment, there was almost no sediment runoff because the vegetation combine with the debris landforms and covered the surface. Therefore, the obvious cause of the channelized debris flows is the collapse of the slope and bed of the gully. Even if the gravel, cobbles, and boulders of the channel bed were lost by debris flow, the thalweg change due to debris flow may not be significant because they are supplied from the gully side slope normally. After the gabion structures were installed, the debris flow increased the thalweg change, bed erosion and side slope of the gully. Various sedimentary structures in the gully were classified according to the factors supporting the sedimentation. The hypsometric curve of the gully reflects the debris landforms and vegetation characteristics of the watershed and the sediment runoff due to debris flow, etc. The relationship between the flow velocity and the hydraulic gradient was non-linear under the condition that the porous medium with gully bed gravels is saturated with water. These results may be used as basic data for channelized debris flow research.

• 수산해양교육연구
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• 제9권1호
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• pp.31-39
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• 1997

Floating debris was recorded from a training ship, #1 Kwanaksan, of Pukyong National University with about 10 knots speed during August 19~26, 1996. The area sampled is the East Coast of Korea, divided into 33 unit segments on survey routes. Debris fabrication materials were categorized using the following; man-made or natural wood items, paper, cardboard, nylon rope, netting, styrofoam and plastics, floating metal and glass containers. All identified items within a $100{\pm}2m$ wide band were recorded but ignored if beyond this boundary. The results of distribution and composition of floating debris in the area are as follows: 1. The quantities of debris during the summer were distributed from 1.8~52 items per $km^2$. The most obvious trend is the widespread distribution of all debris. 2. The highest densities of all debris were discovered in the vicinity of Pusan and ills an area. Especially styrofoam & plastics were observed in 81% of sampled area, next is wood items, 9.1%. Nylon netting & rope was the least widespread pollutant. 3. The relationship between distribution of debris and surface currents of the area was not apparently revealed through this survey. Further surveys are being instigated, and from this it is hoped that a much wider coverage can be achived, perhaps on all sites of Southern and Western sea of Korea and contributed to the finding of sources,stationary area of debris.

• 한국빅데이터학회지
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• 제8권1호
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• pp.73-82
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• 2023

해양쓰레기는 해양생물의 생존, 바닷물 오염, 풍경 등 생태계에 영향을 미칠 뿐만 아니라 2차적으로 경제적 손실 및 인간 건강에 악영향을 끼친다. 수중 및 해수면 쓰레기 문제에 대한 연구는 활발히 진행되고 있는 반면 사람의 접근이 어려운 사각지대의 해양쓰레기 해결방안 연구는 더디게 이뤄지고 있다. 이러한 문제를 해결하기 위해 우리는 드론을 활용해 테트라포드와 같은 사각지대에서 해양쓰레기를 탐지 및 추적한다. 또한 탐지된 쓰레기는 드론의 GPS, 고도, 방위 값 등으로 위치 좌표를 계산해서 이를 시각화한다. 본 연구에서 제안하는 드론을 활용한 해양쓰레기 탐지 및 위경도 매칭 방법은 사각지대에서의 해양쓰레기 문제에 효과적으로 대응할 수 있는 해결책을 제시한다.