• 한국산림과학회지
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• 제90권4호
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• pp.458-464
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• 2001

본 연구는 토양 산성화 정도가 서로 다른 독일가문비나무 임분에서 토양 깊이에 따른 뿌리의 나이테 발달과 분지형태를 분석함으로서, 임분에 따른 뿌리발달을 비교하고자 하였다. 조사된 독일가문비나무 임분에서 뿌리분지구조는 변형된 뿌리와 변형되지 않은 뿌리에 대한 조사임분간의 통계적 유의성이 인정되지 않았지만, 가장 많이 산성화된 Weidenbrunnen 임분에서는 뿌리가 상해를 입음으로 인해 발생되는 포크형, 권총형, 쇠스랑형과 같은 비정상적인 분지구조가 많이 나타났다. 뿌리의 나이테 분석 결과, 수평뿌리의 연평균 길이생장은 Weidenbrunnen 임분과 Barbis 임분이 6.3cm, Eberg$\ddot{o}$tzen 임분이 9.5cm의 길이 생장을 나타내었으며, 수직뿌리의 연평균 길이생장은 Weidenbrunnen 임분이 4.4cm Barbis 임분이 5.4cm, 그리고 Eberg$\ddot{o}$tzen 임분이 6.7cm의 생장을 보였다. 80cm 토양 깊이에서의 뿌리 횡단면 분포는 Eberg$\ddot{o}$tzen 임분이 굵은 뿌리와 가는 뿌리가 고르게 분포하고 있으며, 횡단면의 합계는 $32.6cm^2$ 이었다. Barbis 임분에서는 굵은 뿌리가 가운데 몰려서 분포하고, 가는 뿌리는 비교적 적게 나타났으며, 그 합계는 $29.2cm^2$이었다. Weidenbrunnen 임분에서는 적은 수의 가는 뿌리만 분포하고 그 값은 $10.9cm^2$에 불과하였다. 뿌리고정계수는 Eberg$\ddot{o}$tzen 임분이 1.04로 다른 두 임분 Barbis(0.3), Weidenbrunnen (0.08)과 비교하여 매우 높은 값을 나타내었다. 본 조사 독일가문비나무 임분 중에서 Weidenbrunnen 임분에서 나타난 비정상적인 형태의 변형된 분지구조와 뿌리의 저조한 생장은 토양산 성화 등으로 인하여 정상적인 뿌리가 생장의 장애를 받아 나타난 결과 때문이라 사료된다.

• 소성∙가공
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• 제24권3호
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• pp.187-193
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• 2015

The objective of the current study is to determine cross-sectional profile of intermediate dies in order to improve the plastic strain homogeneity which directly affects not only the dimensional accuracy but also the mechanical properties of final product by redesigning the intermediate dies using the conventional electric field analysis (EFA) method. Initially, the multi-pass shape wire drawing was designed by using the equivalent potential lines from EFA. The area reduction ratio was calculated from the number of passes in multi-pass shape wire drawing but constrained by the capacity of the drawing machine and the drawing force. In order to compensate for a concentration of strain in a region of the cross section of the wire, the process for multi pass wire drawing from initial round material to an intermediate die was redesigned again using the electric field analysis. Both drawing process designs were simulated by the finite element method in which the strain distribution and standard deviation plastic strain of the cross section of drawn wires were examined.

• 센서학회지
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• 제30권3호
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• pp.170-174
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• 2021

As the rising attention to the medical and healthcare issue, Bio-MEMS (Micro electro mechanical systems) platform such as bio sensor, cell culture system, and microfluidics device has been studied extensively. Bio-MEMS platform mostly has high resolution structure made by biocompatible material such as polydimethylsiloxane (PDMS). In addition, three dimension structure has been applied to the bio-MEMS. Lithography can be used to fabricate complex structure by multiple process, however, non-rectangular cross section can be implemented by introducing optical apparatus to lithography technic. X-ray lithography can be used even for sub-micron scale. Here in, we demonstrated lines with round shape cross section using the tilted gold absorber which was deposited on the oblique structure as the X-ray mask. This structure was used as a mold for PDMS. Molded PDMS was applied to the cell culture platform. Moreover, molded PDMS was bonded to flat PDMS to utilize to the sub-micro channel. This work has potential to the large area bio-MEMS.

• 한국해양공학회지
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• 제23권6호
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• pp.131-135
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• 2009

We present an optimum design method for a rectangular reinforced concrete beam using Genetic Algorithms. The optimum design procedure in this paper employs 2 design cases: i) all of the design variables (b, d, As) of the rectangular reinforced concrete section are used pseudo-continuously, ii) one is pseudo-continuous for the concrete cross section (b, d) and the other is discrete, using an index for the steel area (As). The optimum design in this paper uses Chakrabarty's model. In this paper, the Genetic Algorithms use the method of Elitism and penalty parameters to improve the fitness in the reproduction process, which leads to very practical designs. The optimum design of the steel area in the examples uses ASTM standard reinforcing bars (#3~#11, #14, #18).

• 한국정밀공학회지
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• 제22권2호
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• pp.105-112
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• 2005

The guillotined cutting process for the pipe was studied in this paper. Until now guillotining mechanism can not be practically applied in the industries because of the deformation of sheared section around cutting area, the coarse sheared surface, and the burs. To find optimum shapes of blade, several types of blade were experimentally studied. The cutting force normal to the axial direction of the pipe was compared with the theoretical result based on the cutting energy. The experimental maximum cutting forces were very good agreement with the theoretical results. It also discussed that the design parameters of guillotining system such as the blade shape and the clearance between the blade and the die made effects to the deformation of the cutting cross section area. The results show that the guillotining method can be applicable to the pipe cutting system by optimizing the blade shape and the clearance between the blade and the die of the guillotined cutting system with respect to the sheared pipe material.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.711-722
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• 2020

An optimization framework using genetic algorithms has been developed towards an automated parametric optimization of the Octabuoy semi-submersible design. Compared with deep draft production units, the design of the shallow draught Octabuoy semi-submersible provides a floating system with improved motion characteristics, being less susceptible to vortex induced motions in loop currents. The relatively large water plane area results in a decreased natural heave period, which locates the floater in the wave period range with more wave energy. Considering this, the hull design of Octabuoy semi-submersible has been optimized to improve the floater's motion performance. The optimization has been conducted with optimized parameters of the pontoon's rectangular cross section area, the cone shaped section's height and diameter. Through numerical evaluations of both the 1st-order and 2nd-order hydrodynamics, the optimization through genetic algorithms has been proven to provide improved hydrodynamic performance, in terms of heave and pitch motions. This work presents a meaningful framework as a reference in the process of floating system's design.

• 지질공학
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• 제22권3호
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• pp.331-341
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• 2012

화강암류 암석은 일반적으로 절리 발달이 미약하고 단층파쇄대가 잘 발달하지 않는 등 공학적으로 양질의 암석에 해당된다. 그러나 산학지구 붕괴 비탈면을 구성하는 지반은 화강암류로 구성되었음에도 불구하고, 깊은 토사층을 가지며, 불연속면이나 단층 등의 지질구조는 거의 관찰되지 않고, 표층붕괴가 발생한 형태에 해당된다. 본 비탈면의 안정성 고찰을 위해 3가지 경우(현재 단면, 최초 설계 단면, 수정 설계 단면)에 대한 강우지속시간과 간극수압 변화, 안전율 등에 관한 해석을 수행하였다. 강우 지속시간이 길어질수록 지하수위는 높이 20 m까지 상승하는 것으로 나타났으며, 최초 설계단계 단면의 2일 지속강우 기간에는 안전율이 확보되는 것으로 확인되지만, 4일 강우지속기간 동안에는 허용안전율을 만족하지 못하는 것으로 확인되었다. 수정 설계 단면에서는 4일 강우지속기간에도 안전율이 확보되므로 산학 지구는 1:1.8 경사도로 절취하는 것이 영구적인 안정성을 확보하는 방안이라고 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.341-348
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• 2001

The purpose of present study is to investigate for reducing pressure fluctuations in the case of installing the air-shafts on the side wall of the tunnel with small cross-sectional area on conventional line. Experiments were performed with a 1/61-scale moving model rig for the tunnel of 0.764 km length in the condition of tunnel cross-section area of $28 m^2$. According to the results, the maximum pressure fluctuation is reduced by 45 % for 19 air-shafts. This results have the speed-up effects of about 33.4 km/h for the train running in tunnel.

• 한국결정성장학회지
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• 제23권2호
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• pp.67-75
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• 2013

In order to improve osseo-integration of a dental implant with bone crystal we studied an implant with holes inside its body to deliver bioactive materials based on a proposed patent. After bioactive material is absorbed, bone crystal can grow into holes to increase implant bonding in addition to surface integration. The larger cross section area of outlet holes showed the less values of the maximum stress, and the stress concentrations near the uppermost outlet holes were also reduced with an increasing number of outlet holes. The conclusion, that the uppermost outlet design improvement was most effective to reduce the stress concentration and improve the growth rate of bone crystal, could be drawn. After the design optimizations, Type 6-C had provided the best results in this study. The overall shape optimization studies on the shape, location, number, and so on, of the outlet holes, should be carried out further.

• 한국조경학회지
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• 제25권4호
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• pp.39-50
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• 1998

The object of this study was to examine and analyze the environmental deterioration of three major trails and around peak area of Moaksan Provincial park in 1996. Trails are mostly made up at ridgeline and the slope of them is gentle. Mean trail width is 3.6m, and total length of branch trails is 982m in survey area. The environmental deterioration is derived from trail extension. Maximum eroded depth and cross-section area loss are 89cm and 14,050cm2 respectively, and gully erosion type appears at many sites. The environmental deterioration of trails is very heavy at the sections from Khui to Moaksan peak and from Moakchong to ascent part around the peak. The entire width, branch trail, maximum depth, cross-sectional area loss and surface roughness, as the indexes of trail conditions, are significantly greater at the more heavily used trails. Amount of erosion is influenced by eroded depth, longitudinal slope, runoff influence and entire width in descending order as well as the amount of use. Safety and protection facilities on the trail such as stone and soil stairs, rope handrail, stone channel and soil ditch work are built, but they are very deficient. Bared lands about 4,900m2 and fill slopes are caused and formed by recreation activities and constructions around peak area. It is required to carry the recess system and to conserve and rehabilitate the destroyed trail sites and bare fill slopes as soon as possible, before the environmental deterioration becomes critical because of increased used amount in consequence of construction of recreation parks.