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경계요소법에 의한 이종재료 접합면에 수직인 균열의 해석
임원균,이현규 明知大學校 産業技術硏究所 1996 産業技術硏究所論文集 Vol.15 No.-
In the particular situations where the crack is terminated at an interface of two materials, the order of stress singularity depends on the elastic constants which specify the properties of two materials. A multidomain boundary element technique is used to solve a crack normal to bimaterial interface. A correct order of shape function is used for displacement by using the isoparametric elements by shifting adequately the side nodes adjacent to this crack tip. A shape function containing the same order of singularity as that in the interface crack is also used for the interpolation of traction. Numerical testing of a bimaterial with a crack normal to the interface is carried out with three-node elements. The results obtained are compared with the previous solutions.
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小流域 森林의 水收支에 관한 硏究(Ⅱ) : 降雨强度에 의한 流出을 중심으로 with Run-off by Rainfall Intensity
李賢揆 尙志大學校 1997 論文集 Vol.18 No.-
This study was carried out to investigate the water ballance of small catchment (0.51ha) at Wonju Korea. The term of investigate is 1996.4-1996.10 and the item of investigate are the moisture content in soil layer, the Rainfall under tree crown, the Run-off. The results are as follows: 1. The mean of moisture content in forest soil layer is 16.3%, the mean of moisture content in humus layer is 52.8%. and the mean of moisture content in litter layer is 39.6%. 2. The lowest moisture content(1996.5.27-5.30) shows that the moisture content in forest soil layer is 12.8%, moisture content in humus layer is 22.3%, and moisture content in litter layer is 14.5%. 3. The highest moisture content(1996.7.27-7.30) shows that the moisture content in forest soil layer is 18.9%, moisture content in Humus layer is 63.7%, and moisture content in litter layer is 67.8%. 4. The mean of Through fall is 73.8%, and the mean of Stem flow is 2.25%. Through fall of Larix stand is 74.0% and Pinus stand is 73.6%. Stem flow of Larix stand is 2.68% and Pinus stand is 1.83% 5. The rate of Consumtive use is 0.92. the gross pricipitation in forest watershed is 714.3㎥ and the total Run-off is 53.2㎥(1996.7.19-8.2).
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李賢揆 尙志大學校 1998 論文集 Vol.19 No.-
Most denuded mountain-areas in Korea were completely stabilized by the successful work of the 1st and 2nd 10=years Forest Development plans which targeted the reforestation of denuded forest lands(the total area of denuded forest land was 680 thousand ha in the 1950s). The objectives of this peper are (1) to estimate the depth of organic horizon in the soil profile, (2) to investigate the change of vegetation structure, (3) to estimate the change of biomass in the erosion controlled and rehabilitated mountain areas with the passage of time. This study was carried out as the third times. The first study began in 1985 year, the second study was in 1988, the third study was in 1992 year. When the first study started, the sites have elapsed 3 years (site I), 5 years(siteII), 7 years(site III), 9 years(siteIV) after erosion controlled work. The results of the study were as follows : The change of organic horizon thickness was 5 cm, during 16 years after erosion control work. The Al horizon come out after 16 years. Change of vegetation structure on upper plant layer: R.C of Robinia Puseudoacacia gradually increase, R.C, of Quercus spp. continuously incress. On the whole, the young growths of Alnus spp, have not appear on the soil surface. Biomass of herb have not almost appear all the site after 10years. On 16 years, dry weight of vegetation in erosion controlled area was 62.5t/ha.
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이현규,이상순 한국반도체디스플레이기술학회 2019 반도체디스플레이기술학회지 Vol.18 No.3
This paper describes the results of a study on the unmanned maintenance robot that simultaneously performs the cleaning and inspection of the photovoltaic panels. The robot has a special adsorptive device, an infrared sensor, a vacuum level sensor and a camera. The robot uses two SSC (Sliding Suction Cup) adsorptive devices to move up and down the slope. First, the forces generated when the robot moves up the slope are mechanically analyzed, and the required design and control of the adsorption system are suggested. The robot was designed and manufactured to operate stably by using the presented results. Next, the normal force between the panel and the wheel was measured to confirm that the robot was manufactured and operated as intended, and the robot motion was tested on the inclined panel. It has been proven that robots are well designed and built to clean and inspect sloped panels.
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전해Ni, 무전해 Ni pad에서의 Cu 함량에 따른 접합 신뢰성에 관한 연구
이현규,천명호,추용철,오금술,Lee, Hyun Kyu,Chun, Myung Ho,Chu, Yong Chul,Oh, Kum-Sool 한국마이크로전자및패키징학회 2015 마이크로전자 및 패키징학회지 Vol.22 No.3
It has been used various pad finish materials to enhance the reliability of solder joint and recently Electroless Ni Electroless Pd Immersion Gold (the following : ENEPIG) pad has been used more than others. This study is about reliability according to being used in commercial Electrolytic Ni pad and ENEPIG pad, and was observed behavior of various Cu contents. After reflow, the inter-metallic compound (IMC) between solder and pad is composed of $Cu_6Sn_5$ (Ni substituted) by using EDS, and in case of ENEPIG, between IMC and Ni layer was observed the dark layer ($Ni_3P$ layer). Additional, it could be controlled the thickness of dark layer according to Cu contents. Investigated the different fracture mode between electrolytic Ni and ENEPIG pad after drop shock test, in case of soft Ni, accelerated stress propagated along the interface between $1^{st}$ IMC and $2^{nd}$ IMC, and in case of ENEPIG pad, accelerated stress propagated along the weaken surface such as dark layer. The unstable interface exists through IMC, pad material and solder bulk by the lattice mismatch, so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface. Therefore, it is strongly requested to control solder morphology, IMC shape and thickness to improve the solder reliability. 솔더 조인트의 신뢰성 강화를 위해서 다양한 pad finish material이 사용되고 있으며, 최근에는 Electroless Ni Electroless Pd Immersion Gold (이하 ENEPIG) pad가 많이 사용되고 있다. 따라서, 본 연구는 상용화 되어 사용중인 Electrolytic Ni (soft Ni) pad와 최근 이슈가 되고 있는 ENEPIG pad에 대한 신뢰성 평가에 관한 것으로, 다양한 Cu 함량에 따른 거동을 관찰 하였다. Reflow 후 솔더와 pad간의 접합층은 $Cu_6Sn_5$에 Ni이 치환된 형태의 금속간 화합물로 구성되어 있었으며, ENEPIG pad의 경우, 접합층과 Ni layer 사이에 $Ni_3P$ (dark layer) layer가 관찰 되었다. 또한, Cu 함량에 따라 Dark layer의 두께를 제어할 수 있었다. 충격 낙하 시험 후, 파괴모드를 관찰한 결과 soft Ni pad와 ENEPIG pad에서 서로 다른 파괴모드가 관찰 되었으며, soft Ni의 경우, 1차 IMC와 2차 IMC 경계에서 파괴가 관찰 되었고, ENEPIG pad의 경우, dark layer에서 파괴가 관찰 되었다. IMC와 pad material, bulk 솔더와의 lattice mismatch에 의해 불안정한 계면이 존재하며, 이는 연속적인 외부 충격에 의해 가해진 열적, 물리적 스트레스를 IMC 계면으로 전송하기 때문에, 솔더의 신뢰성 향상을 위해서는 솔더 벌크의 제어와 IMC의 두께 및 형상의 제어는 필요하다.
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