• Journal of the Korean Wood Science and Technology
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• 제43권2호
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• pp.145-155
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• 2015

Fiber morphology and basic characteristics of Legi bamboos (Gigantochloa atter) growing on Yogyakarta were studied considering their age and height positions in the culms. Culms of 4, 16, and 40 months were harvested, and their total lengths were measured. The length, diameter, and wall thickness of each internode were measured. All the sample culms were divided into three different parts along the height, and their fiber dimension and physical properties were observed. The data obtained were analyzed by analysis of variance. The results showed that the culms had a diameter of 5.8 to 10.8 cm. The lowest internodes always showed the shortest length and the thickest wall. The culms had an average fiber length of 2.41 mm and Runkel ratio of 0.61. Fiber length was affected by the height, while fiber diameter, lumen diameter, and fiber wall thickness were affected significantly by the age of the culms. The culms had high green moisture content (GMC) of 157.89%, and basic density (BD) of $456.67kg.m^{-3}$, a total longitudinal shrinkage of 0.35%, and relatively low R/T shrinkage ratio. The interactions between age and height were affected GMC and BD.

• 한국가스학회지
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• 제14권4호
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• pp.45-50
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• 2010

해저배관의 안전성 검토를 위하여 수압에 의한 소성붕괴 저항성을 평가하였다. 본 연구에서는 해저배관에 부가되는 주하중을 수압으로 설정하여 배관의 직경대 두께비와 ovality 변화가 배관의 소성붕괴 변화에 미치는 영향을 유한요소해석을 통하여 평가하였다. 내압은 외압에 의한 소성붕괴 저항성을 향상시켜 소성붕괴 발생 깊이를 증가시켰으며, 동일 ovality에서 local ovality를 갖는 배관은 global ovality 보다 더 깊은 붕괴 깊이를 나타내었으며, 소성붕괴 발생 깊이는 직경대 두께비의 증가 또는 ovality 증가에 따라 감소하였다.

• Steel and Composite Structures
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• 제18권2호
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• pp.519-546
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• 2015

This study addresses the load capacity prediction of circular concrete-filled steel tube (CFST) columns under axial compression using current design codes. Design methods given in the Chinese code CECS 28:2012 (2012), American code AISC 360-10 (2010) and EC4 (2004) are presented and described briefly. A wide range of experimental data of 353 CFST columns is used to evaluate the applicability of CECS 28:2012 in calculating the strength of circular CFST columns. AISC 360-10 and EC4 (2004) are also compared with the test results. The comparisons indicate that all three codes give conservative predictions for both short and long CFST columns. The effects of concrete strength, steel strength and diameter-to-thickness ratio on the accuracy of prediction according to CECS 28:2012 are discussed, which indicate a possibility of extending the limitations on the material strengths and diameter-to-thickness ratio to higher values. A revised equation for slenderness reduction factor in CECS 28:2012 is given.

• 대한기계학회논문집B
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• 제30권6호
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• pp.505-513
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• 2006

The pressure drop characteristics in a rotating two-pass duct with rib turbulators are investigated in the present study. Three ducts of different aspect ratios (W/H=0.5, 1.0 and 2.0) are employed with a fixed hydraulic diameter ($D_h$) of 26.7 mm. $90^{\circ}$-rib turbulators with $1.5mm{\times}1.5mm$ cross-section are attached on the leading and trailing surfaces. The pitch-to-rib height ratio (p/e) is 1.0. The distance between the tip of the divider and the outer wall of the duct is 1.0 W. The thickness of divider wall is 6.0 mm o. 0.225 $D_h$. The Reynolds number (Re) based on the hydraulic diameter is kept constant at 10,000 and the .elation number (Ro) is varied from 0.0 to 0.2. As duct aspect ratio increases, high friction factor ratios show in overall regions. The reason is that the rib height-to-duct height ratio (e/H) increases, but the divider wall thickness-to-duct width ($t_d/W$) decreases. The rotation of duct produces pressure drop discrepancy between the leading and trailing surfaces. However, the pressure drop discrepancy of the high duct aspect ratio (AR=2.0) is smaller than that of the low duct aspect ratio (AR=0.5) due to the decrement of duct hight (H).

• 한국환경복원기술학회지
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• 제13권4호
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• pp.10-17
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• 2010

The objectives of this study were to compare the growth of Vitex rotundifolia as affected by the difference of soil depth and mixture ratio in a shallow-extensive green roof module system, and to identify the level of soil thickness and mixture ratio as suitable growing condition to achieve the desired plant growth in green roof. Different soil thickness levels were achieved under 7cm, 15cm and 25cm of shallow-extensive green roof module systems made by woody frame of $500{\times}500{\times}300mm$. Soil mixture ratio were eight types for perlite : peatmoss : leafmold = 7 : 1 : 2 (v/v/v, $P_7P_1L_2$), perlite : peatmoss : leafmold = 6 : 2 : 2 (v/v/v, $P_6P_2L_2$), perlite : peatmoss : leafmold = 5 : 3 : 2 (v/v/v, $P_5P_3L_2$), perlite : peatmoss : leafmold = 4 : 4 : 2 (v/v/v, $P_4P_4L_2$), only sand ($S_{10}$), sand : leafmold = 7 : 3 (v/v, $S_7L_3$), sand : leafmold = 5 : 5 (v/v, $S_5L_5$) and only leafmold ($L_{10}$). The growth response of Vitex rotundifolia had fine and sustain condition in $P_6P_2L_2$, $P_5P_3L_2$ and $P_4P_4L_2$., Especially, in case of $P_6P_2L_2$, growth response appeared to be good even in soil thickness 7cm, which showed low survival rates of Vitex rotundifolia in other soil mixtures. Tree height, root diameter, photosynthesis and chlorophyll contents tended to increase with increased soil thickness.

• Tribology and Lubricants
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• 제23권3호
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• pp.103-108
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• 2007

In this paper, the optimized design and strength analysis have been presented based on the finite element and Taguchi's experimental methods. The stress, strain and displacement characteristics of OPC drum tubes are affected by rolling contact pressures between an OPC drum tube and a paper, design parameters of an aluminum tube and material properties. The OPC drum tubes with nine different geometrical models are analyzed for design parameters that are related to the outer diameter, the thickness, and the length of an aluminum tube for a toner cartridge. The optimized design parameters for an aluminum tube may be selected as the outer diameter of 28 mm, the thickness of 0.8 mm, and the length of 220 mm. But the currently used aluminum tube for a laser printer is fairly optimized based on the Taguchi's design analysis. The calculated FEM results showed that the affection ratio of the design parameter t, which may control the strength of an aluminum tube, is the most influential parameter among the length and an outer diameter of a tube.

• 소성∙가공
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• 제19권2호
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• pp.79-87
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• 2010

The Pipe bending process using high frequency local induction heating is an advanced technique to bend pipes with a small bending radius and a large diameter. Even though the pipe bending process is a quite widespread engineering practice, it depends heavily upon trial and error method by field engineers with several years of experience. So it is necessary to develop an integrated methodology for optimum design of the pipe bending process. During hot pipe bending using induction heating, outward wall thickness of a pipe is thinned due to tensile stress and the reduction of wall thickness is not allowed to exceed 12.5%. Taguchi method and dynamic reverse moment is proposed to maintain a reduction ratio of thickness within 12.5%, when D/t ratio is high. An application of the proposed approach was compared with those of the finite element analysis and has good in agreements.

• 한국연초학회지
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• 제4권2호
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• pp.41-50
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• 1982

To investigate tile effects of growth characteristics on the yield, price per Kg, chemical contents and physical properties in Burley tobacco, ten varieties including Burley 21 were tested in this study. The results obtained are summarized as follows. 1 Forty to fifty days after transplanting, CCR (Crop Growth Rate) was the highest. RCR (Relative Growth Rate) increased up to 40 days, but decreased 50 days when maturation began. High- yielding varieties showed high CCR and RCR till 60 days. 2. Total alkaloid content of cured leaf increased about three times than that of topping stage, but the increased rates were some what different among varieties. 3. Leaf area, stalk diameter, stalk height and days to flower showed positive correlations to yield, whereas leaf thickness and weight per unit leaf area showed negative. 4 Varieties which are high in cured leaf weight ratio and weight per unit leaf thickeners showed relatively poor quality. 5 Nitrogen content was high in leafy and larger stalk diameter variety. 6. There are positive correlation between weight per unit leaf thickness and filling power. The time of combustion was positively correlated to leaf thickness and weight Per unit leaf. 7. It can be concluded that many characteristics are related to the yield, but not quality. It is, there fore, easy to Predict tile yield, but difficult to forecast the qualiffy.

• 소성∙가공
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• 제15권1호
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• pp.9-14
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• 2006

In the present research, the simultaneous punching of ultra small size hole of $2\~10\;{\mu}m$ in diameter on flat rolled thin metal foils was conducted with elastic polymer punch. Workpiece used in the present investigation were the rolled pure copper of $3{\mu}m$ in thickness and CP titanium of 1.5fm in thickness. The metal foils were punched with the dies and arrays of circular and rectangular holes were made. The process set-up is similar to that of the flexible rubber pad farming or Guerin process. Arrays of holes were punched successfully in one step forming. The punched holes were examined in terms of their dimensions. The effects of the wafer die hole dimension and heat treatment of the workpiece on ultra small size hole formation of the thin foil were discussed. The process condition such as proper die shape, pressure, pressure rate and diameter-thickness ratio (d/t) were also discussed. The results in this paper show that the present method can be successfully applied to the fabrication of ultra small size hole away in a one step operation.

• Steel and Composite Structures
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• 제7권4호
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• pp.303-320
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• 2007

The objective of this study is to clarify the structural features of members consisting of connection, as a series of the previous study on the CFT column-to-beam tensile connection with combined cross diaphragm. This connection has the merits that the stress is distributed evenly on the beam flange and the diaphragm and the stress concentration is reduced, by improving the stress transfer route and restraining abrupt deformation of diaphragm. The finite element analysis was performed to find out the stress transfer through sleeve which is an important member of the connection with combined cross diaphragm. The length and thickness of sleeve were used as variables for the analysis. As the analysis results, the length and thickness of sleeve didn't influence on the capacity of the connection and played a role of a medium to transfer the stress from the diaphragm to the filled concrete. It is proposed that the appropriate length of sleeve be the same value as the diameter of sleeve and the appropriate ratio of sleeve diameter to sleeve thickness be 20. Two equations for evaluation of the load-carrying capacity of the connection were also proposed through the modification of the evaluation equation suggested in the previous study.