• Steel and Composite Structures
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• v.44 no.3
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• pp.309-324
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• 2022

The post-fire elastic stiffness and performance of concrete-filled steel tube (CFST) columns containing recycled aggregate concrete (RAC) has rarely been addressed, particularly in terms of material properties. This study was conducted with the aim of assessing the modulus of elasticity of recycled aggregate concrete-filled steel tube (RACFST) stub columns following thermal loading. The test data were employed to model and assess the elastic modulus of circular RACFST stub columns subjected to axial loading after exposure to elevated temperatures. The length/diameter ratio of the specimens was less than three to prevent the sensitivity of overall buckling for the stub columns. The gene expression programming (GEP) method was employed for the model development. The GEP model was derived based on a comprehensive experimental database of heated and non-heated RACFST stub columns that have been properly gathered from the open literature. In this study, by using specifications of 149 specimens, the variables were the steel section ratio, applied temperature, yielding strength of steel, compressive strength of plain concrete, and elastic modulus of steel tube and concrete core (RAC). Moreover, parametric and sensitivity analyses were also performed to determine the contribution of different effective parameters to the post-fire elastic modulus. Additionally, comparisons and verification of the effectiveness of the proposed model were made between the values obtained from the GEP model and the formulas proposed by different researchers. Through the analyses and comparisons of the developed model against formulas available in the literature, the acceptable accuracy of the model for predicting the post-fire modulus of elasticity of circular RACFST stub columns was seen.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.2
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• pp.226-230
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• 1986

Two near-isogenic lines with dark and pale green leaves, derived from the F$\_$7/ generation of wxl26 cross were compared on photosynthetic capacity, growth parameters, grain yield and yield-related characters. Dark green-leaved lines contained much greater content of chlorophyll a and b than pale green-leaved ones, but chlorophyll a to b ratio showed no difference between them. The photosynthetic nte per unit leaf area was higher in dark green-leaved lines than in pale green-leaved ones in the flag leaves at heading stage, but that per unit chlorophyll content showed reversed result. The crop growth rate from transplanting to heading was consistantly higher in the dark green-leaved lines, resulting from their greater net assimilation rate. Dark green-leaved lines produced greater number of panicles and spikelets per hill, out yielding pale green-leaved lines, but ripened grain ratio and 1000-grain weight showed no differences between those lines.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.177-184
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• 2000

The effect of the buyancy and thermocapillarity for differnent aspect ratio of flow field on melt motion and mass transfer has been numerically investigated in magnetic Czochralski crystal growth of silicon. During the process of crystal growth, the melt depth of crucible reduces so the aspect ratio of flow field also reduces. Therefore the shape of magnetic field of the flow field changes and the flow pattern also changes significantly. Together with the melt flow which forms the Marangoni convection (or thermocapillary flow) that comes from the inside the flow field, a flow circulation is observed near the corner close both to the crucible wall and the free surface. Due to this circulation, buoyancy effect has been turned out to be local rather than global. As the aspect ratio decreases, the radial component of the magnetic field prevails compared with the axial component in the flow field. Under the influence of this magnetic field, the melt flow and the temperature distribution in a meridional plane tend to depend on the radial position. As the aspect ratio decreases, the temperature gradient near the edge of the crystal decreases yielding smaller thermocapillarity, and the oxygen concentration near the crystal and the oxygen incorporation rate also decrease.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.1
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• pp.26-32
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• 1985

Ten recommended rice varieties were cultivated in paddy area affected by air-pollutants and in normal area to select varieties adaptable to air-pollution environment. Rice plants grown in pollution site showed higher contents of total sulfur and fluorine in leaf through the whole growing period compared with those in non-pollution site, and rice leaves destroyed by air-pollutants were found only in pollution site. Rice grain yield and four yield components of ten rice varieties grown in pollution site were lower than those in normal area. Five rice varieties among ten were selected as adaptable to air-pollution environment, based on their yielding potential in pollution site and grain yield ratio between two sites. Rice varieties adaptable to pollution showed little variation of percent ripened grains and number of panicles per hill between two sites. Chlorophyll content in flag leaf of rice plants grown in pollution area was lower than in non-pollution area. No relationship was found between grain yield ratio (pollution/non-pollution site) of ten varieties and total sulfur content ratio, fluorine content ratio, chlorophyll content ratio between two sites, and percent destroyed leaf in pollution site, respectively. This result suggest that varietal adaptability to air-pollution environment is not related with the amount of pollutants absorbed, but with the degree of response to pollutants.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.147-157
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• 2018

The basis of capacity design has been explicitly or implicitly regulated in most bridge design specifications. It is to guarantee ductile failure of entire bridge system by preventing brittle failure of pier members and any other structural members until the columns provides fully enough plastic rotation capacity. Brittle shear is regarded as a mode of failure that should be avoided in reinforced concrete bridge pier design. To provide ductility behavior of column, the one of important factors is that flexural hinge of column must be detailed to ensure adequate and dependable shear strength and deformation capacity. Eight small scale circular reinforced concrete columns were tested under cyclic lateral load with 4.5 aspect ratio. The test variables are longitudinal steel ratio, transverse steel ratio, and axial load ratio. Eight flexurally dominated columns were tested. In all specimens, initial flexural-shear cracks occurred at 1.5% drift ratio. The multiple flexural-shear crack width and length gradually increased until the final stage. The angles of the major inclined cracks measured from the vertical column axis ranged between 42 and 48 degrees. In particular, this study focused on assessing transverse reinforcement contribution to the column shear strength. Transverse reinforcement contribution measured during test. Each three components of transverse reinforcement contribution, axial force contribution and concrete contribution were investigated and compared. It was assessed that the concrete stresses of all specimen were larger than stress limit of Korea Bridge Design Specifications.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.43-51
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• 2017

As per current seismic design codes, diagonally reinforced coupling beams are restricted to coupling beams having aspect ratio below 4. However, a grouped diagonally reinforcement detail makes distribution of steel bars in the beam much harder, furthermore it may result in poor construction quality. This paper describes the experimental results of concrete coupling beam reinforced with high-strength steel bars (SD500 & SD600 grades). In order to improve workability for fabricating coupling beams, a headed large diameter steel bar was used in this study. Two full-scale coupling beams were fabricated and tested with variables of reinforcement details and aspect ratio. To reflect real behavior characteristic of the beam coupling shear walls, a rigid steel frame system with linked joints was set on the reaction floor. As a test result, it was noted that cracking and yielding of reinforcement were initially progressed at the coupling beam-to-shear wall joint, and were progressed to the mid-span of the coupling beam, based on the steel strain and failure modes. It was found that the coupling beams have sufficient deformation capacity for drift ratio of shear wall corresponding to the design displacement in FEMA 450-1. In this study, the headed horizontal steel bar was also efficient for coupling beams to exhibit shear performance required by seismic design codes. For detailed design for coupling beam reinforced with high-strength steel, however, research about the effect of variable aspect ratios on the structural behavior of coupling beam is suggested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.71-77
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• 2019

Recently, most of the pile foundations have been applied as a method to transfer the heavy load of the structure to the ground with high bearing capacity. In this study, the pile-cap behavior between foundation and hollow-head precast reinforced concrete(HPC) pile reinforced with longitudinal rebar and filling concrete was experimentally evaluated depending on the cyclic load and reinforcement ratio. As the drift ratio increases, it was found that the cracks pattern and fracture behavior of two types of pile-cap specimens according to the reinforcement ratio were evaluated to be similar. As the reinforcement ratio increases by 1.77 times, the BS-H25 specimen increases the maximum load by 1.47 times compared to the BS-H19 specimen. However, the ductility ratio of positive and negative was decreased by 76% and 70% respectively. After the yielding of the pile-cap reinforcing rebars, the positive and negative stiffness of the all specimens were decreased by a range from 66% to 71% and a range from 54% to 57% respectively, and the average stiffness of BS-H25 specimen is 13% higher than that of BS-H19 specimen. The cumulative dissipated energy capacity of BS-H19 and BS-H25 specimen under ultimate load state is 5.5 times and 6.6 times higher than that of service load state.

• Korean Journal of Poultry Science
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• v.24 no.4
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• pp.185-191
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• 1997

In order to obtain the basic information needed to utilize poultry by-products as feed resources, the yielding ratio, chemical composition and nutrient bioavailability of 5 offal components such as autoclaved head, feet, viscera, blood and feathers were investigated. Yielding ratios of head, feet, viscera, blood and feathers were 2.93％ 4.78％, 10.98％, 3.91％ and 4.83％, respectively. The crude protein contents of feathers (86.71％) and blood (82.99％) were higher than those of viscera (64.67％), feet (58.76％) and head (49.51％) , Inversely, the crude fat contents of blood (6.96％) and feathers (2.96％) were lower than those of head (26.19％), viscera (23.96％) and feet (13.73％). The crude ash contents of feet (21.69％) and head (20.38％) were higher than those of other by-products (0.96∼8.62％). The macro-mineral contents of head and feet were higher than those of other components, and the iron content of blood was higher than the other by-products. The total amino acid contents of poultry by-products showed the same trend as the crude protein contents. In addition, the Iysine content of feathers was very low compared to its high protein content. The essential amino acid contents of feathers were poorer than those of other offal components. Among the 5 offal components, the feathers showed the poorest amino acid availabilities. The ME contents were highest in viscera, and head, blood, feathers and feet. in decreasing order.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.3
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• pp.142-146
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• 2003

To obtain information on the inheritance of grain weight and grain size of japonica cultivar, Sobibyeo which has high yielding potential and large grain in rice, the genetic variation, heritability and phenotypic correlation of 1,000 grain weight, grain length, width and thickness were investigated in two crosses, Iksan 429/Sobibyeo and Iksan 430/Sobibyeo. The gram characteristics of $\textrm{F}_1$ hybrids exceeded mid-parental values, while grain length: width ratio was intermediate between the parents. In $\textrm{F}_2$ populations, the average grain length, width and thickness were intermediate as mid-parental values, but grain weight exceeded the mid-parental values. In $\textrm{F}_2$ populations of Iksan 429/Sobibyeo and Iksan 430/Sobibyeo, mean 1,000 grain weights were 24.86g and 25.04 g on the average, and ranged 18.4g-32.2g and 19.5g-33.4g, respectively. The segregation mode for grain weight was regarded as a nearly normal distribution in two crosses of $\textrm{F}_2$ populations. Estimates of broad sense heritabilities for grain weight in Iksan 429/Sobibyeo and Iksan 430/Sobibyeo were high as 89.00% and 89.06%, and grain length showed the highest heritability among grain characteristics as 97.45% and 97.35%, respectively. Grain weight was highly correlated with grain length, width and thickness, and grain length was highly correlated with grain width and thickness. These grain characteristics were apparently controlled by polygenes. Accordingly, these traits will be readily improved through selection in the early segregating generations.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.542-550
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• 2020

The use of high-strength aluminum alloys for ships and of shore structures has many benefits compared to carbon steels. Recently, high-strength aluminum alloys have been widely used in onshore and of shore industries, and they are widely used for the side shell structures of special-purpose ships. Their use in box girders of bridge structures and in the topside of fixed platforms is also becoming more widespread. Use of aluminum material can reduce fuel consumption by reducing the weight of the composite material through a weight composition ratio of 1/3 compared to carbon steel. The characteristics of the stress strain relationship of an aluminum structure are quite different from those of a steel structure, because of the influence of the welding[process heat affected zone (HAZ). The HAZ of aluminum is much wider than that of steel owing to its higher heat conductivity. In this study, by considering the HAZ generated by metal insert gas (MIG) welding, the buckling and final strength characteristics of an aluminum reinforcing plate against longitudinal compression loads were analyzed. MIG welding reduces both the buckling and ultimate strength, and the energy dissipation rate after initial yielding is high in the range of the HAZ being 15 mm, and then the difference is small when HAZ being 25 mm or more. Therefore, it is important to review and analyze the influence of the HAZ to estimate the structural behavior of the stiffened plate to which the aluminum alloy material is applied.