• Korean Journal of Environmental Agriculture
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• v.22 no.1
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• pp.60-64
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• 2003

This study was conducted to examine the effects of plug tray cell size and growth media on good seedling production of Gerbera hybrida Hort. Seedlings were grown for 60 days in 50, 72, 128, 162 cell trays contanning perlite, cocopeat and perlite+cocopeat(1:1, v/v). Perlite showed higher bulk density than cocopeat and perlite+cocopeat. Total porosity was greater in perlite, cocopeat and perlite+cocopeat in order. Cocopeat showed the highest water holding capacity. Number of leaves were greatest in 128 cell tray containing cocopeat. Leaf area was greatest in 50 cell tray containing cocopeat. Seedling growth was also better in plug tray of bigger cell size. Seedling growth of fresh and dry weight of shoot and root was much better in the growth media of perlite+cocopeat.

• Proceedings of the KWS Conference
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• 1999.05a
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• pp.72-73
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• 1999

• Journal of Korea Foundry Society
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• v.7 no.spc
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• pp.271-278
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• 1987

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.807-813
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• 1986

The orthogonal cutting method of the nodular graphite cast iron in the lathe turning, whose matrix were formulated under two kinds of annealing conditions, has been experimentally studied and the results investigated. The various characteristics of machinabilities of the nodular cast iron, depending upon its matrix, have been obtained from the results as follows. (1) As depth of cut increases, the cutting ratio and the shear angles tend to slightly increase, and as the containing quantity of ferrite matrix increases, they slightly decrease. (2) As depth of cut increases, the cutting force increases in an approximate straight line, and as the containing quantity of ferrite matrix increases, they decreases and the decreasing rate is about 20-30%. (3) As the containing quantity of ferrite matrix increases, the friction force acting on the tool face decreases and the decreasing rate is about 34-40% in case of the lower depth of cut, but in case of the higher depth of cut the decreasing rate is very small. (4) Both shearing force and vertical force show a lineal increases, and according as ferrite matrix increases there is a decrease by 25% in shearing force and a 12-25% decrease in vertical force. (5) Shearing speed and chip flow speed keep almost a constant value irrespective of matrix.

• Journal of Korea Foundry Society
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• v.26 no.4
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• pp.180-183
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• 2006

The effects of adding Ni on microstructure and mechanical properties of Nodular Indefinite Chilled Iron (NICI) were studied. Thermal fatigue, hardness, tensile properties, wear resistance, are very important factors for NICI used for hot working roll and wire rod mill. The results show that addition 4% nickel has changed pearlite to bainite. Bainite matrix is superior to pearlite matrix on wear resistance, hardness and strength and will increase performance lifetime of NICI conventional roll material. Based in the bainitic microstructure, hardness and tensile property increase up to 48 HRc and $72\;kg/mm^2$, respectively.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.523-528
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• 2002

콤바인 예취날의 내구성을 향상시키고자 예취날 성분분석을 한 다음 적정한 고주파열처리 방법을 구명하고자 예취날 단면 형상별, 가열 시간별, 냉각수 처리속도별로 시험한 후 경도 및 조직특성을 분석한 결과는 다음과 같다. 가. 국산 2종, 수입날 2종에 대한 성분분석 결과 국산 2종의 구성성분은 원소재인 SK5의 KS규격 범위내에 있고, 다만 수입날 1종의 Mn만이 0.7로 기준치인 0.5를 초과하고 있었다. 나. 고주파 코일 단면 형상에 따른 열처리시험에서 사각형 코일이 원형보다 경도가 약간 높게 나타나 사각형 코일 열전달 효율이 좋은 것으로 나타났으며, 시편에 가열하는 시간은 14sec, 냉각수의 처리속도는 Isec에서 가장 좋은 경도값을 나타내었다. 다. 고주파 열처리한 예취날 예취부의 평균 로크웰경도(H$_{R}$C)는 기존날 52.9, 개량날 62.0, 일산날 57.1로 나타나 개량날이 기존날에 비해 17% 경도가 높게 나타났다. 라. 예취날 볼트 고정부의 평균 경도는 기존 국산날이 39.3, 고주파열처리한 개량날 6.1, 일산날 9.3으로 고정부의 경도가 높으면 예취날이 깨어지는 경향이 있어 낮아야 하는데 국산날의 경우 상대적으로 높게 나타났다. 마. 예취날의 조직은 기존 국산 예취날의 경우 취성이 많고 강도가 약한 퍼얼라이트(Pearlite) 또는 미세퍼얼라이트(Fine Pearlite) 조직이었으나 일산날과 고주파열처리에 의한 개량날은 강도가 높고 내마모성이 강한 마르텐사이트(Martensite) 조직을 형성하고 있었다.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1995.04a
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• pp.70-71
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• 1995

양액재배에 이용되고 있는 배지의 종류는 여러 가지가 있으나 조제, 관리 및 작물의 생육 등 여러가지 조건을 동시에 충족시킬만한 배지는 별로 없다. 우리 나라에서는 훈탄, 자갈 등의 배지가 사용되다가 최근 들어 퍼얼라이트, 암면 등이 주종을 이루고 있는데, 이들의 경우 사용 후의 처리와 소독이 문제시되고 있을 뿐만 아니라 가격이 비싸기 때문에 양액재배 시설비용의 상승원인이 되기도 한다. (중략)

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.3
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• pp.79-84
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• 1998

It is very difficult to analyze the transient temperature distribution during quenching of the steel because of coupled effects among temperature, structures and stresses. In this paper, using Inoue's equation of evolution and mixture rule, transient temperature distribution is calculated by the finite element method considering latent heat of transformation structure and temperature dependence of physical and mechanical prperties for the 0.45% carbon cylindrical steel bar with 40mm diameter and 20mm height during end-quenching.

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.78-79
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• 2000

• Resources Recycling
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• v.9 no.1
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• pp.15-20
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• 2000

The effect of different kinds of steel scraps, the raw material in the manufacturing of nodular cast iron, on the microstructures and mechanical properties has been investigated Different grades were produced by changing the steel scraps. When nodular graphite cast iron was produced by using Zn rich steel scrap, such as galvanized steel sheet and auto body sheet, mechanical properties were deteriorated due to the decomposition of graphite, so close control must be maintained over this element. Tensile strength and hardness of nodular graphite cast iron which were manufactured by using Sb rich steel scrap were increased while elongation was decreased due to the increased amounts of pearlite within matrix. Mn and Cr contents in the structural steel sheet scrap or malleable iron scrap increased tensile strength and hardness of nodular graphite cast iron by facilitating the formation of pearlite.