• Journal of Biosystems Engineering
• /
• v.43 no.4
• /
• pp.362-368
• /
• 2018

Purpose: Self-sufficiency in paper production is desired in Nigeria. This study was aimed at evaluating the performance of a locally fabricated batch pulp digester. Methods: The pulp yields of sheaths generated as waste in the production of bamboo (Bambusa vulgaris) laminates were determined at different liquor concentrations and treatment time after preliminary experiments to ascertain the conditions under which the sheath started to pulp. Moreover, the optimum pulping conditions and fiber characteristics were determined and estimated, respectively, to ascertain the pulp fiber suitability for paper production. Results: An optimum pulp yield of 65.1% was obtained at 50% NaOH and 25% $Na_2S$ liquor concentration (w/w) when the cooking time was 4 h. The results of fiber characterization of the pulp indicated an average fiber length of 2.19 mm with a low Runkel ratio of 1.63, both of which signify the suitability of the pulp for medium quality paper production. Conclusions: Softwood pulp can be blended with the fibers to improve the strength of the produced paper; further investigation should be carried out to use other non-woody plants for pulp and papermaking.

• Korean Journal of Weed Science
• /
• v.8 no.1
• /
• pp.64-70
• /
• 1988

An experiment was carried out to know the effects of paclobutrazol on the lodging related traits and yield of a japonia (Seomjinbyeo) and an indica (Samgangbyeo) rice variety grown at 3 N levels (10, 20, 30 kg/10a) and 3 N split rates [basal + top dressing 15 days after transplanting (DAT) : top dressing 25 days before heading (DBH) was 100 : 0, 80 : 20, and 60 : 40]. Paclobutrazol (3kg/10a of 0.6% G) was applied 15 DBH and lodging related traits were observed 3, 13, 23, and 33 days after heading (DAH). The results obtained summarized as follows. 1. Culm length was increased as N level increased, but decreased by application of paclobutrazol. Culm length was not affected by N split rates in both varieties. 2. Lodging was not occurred at all plots, but lodging index of Seomingbyeo was much greater than that of Samgangbyeo. In both varieties loding index increased up to 23 DAH due to an increase in fresh weight and a decrease in breaking strength and levelled off thereafter due to a decrease in both fresh weight and breaking strength. 3. Culm length of Seomjinbyeo and fresh weight of shoot and culm length of Samgangbyeo were positively correlated with lodging index, but breaking strength was not correlated with lodging index in both varieties during the most of ripening stages. Direct effect of culm length contributing to lodging index was positive and much greater than that of fresh weight and breaking strength in Seomjinbyeo, but in Samganbyeo direct effect of culm length and fresh weight was positive, but that of breaking strength was negative with similar magnitudes. 4. Yield in brown rice of Seomjinbyeo was not affected by N level, but split application of N increased yield. In contrast, yield of Samgangbyeo was increased as N level increased, but yield was not affected by N split rates. Paclobutrazol did not affect yield of rice in Seomjinbyeo, but decreased yield by 5.2% in Samgangbyeo due to a decrease in the number of spikelets per panicle.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.2 s.20
• /
• pp.53-60
• /
• 2006

The shear failure modes of reinforced concrete members using high-strength materials (high-strength concrete and high-strength steel) are different to those of reinforced concrete members using normal-strength materials. The reinforced concrete members using high-strength materials are inclined to fail due to concrete crushing before the shear reinforcing bar reaches its yield strength. This paper presents an evaluation equation to calculate the maximum shear reinforcement ratio based on the material stresses and strains when the reinforced concrete members fail in shear. The maximum shear reinforcement ratio calculated by the proposed equation increases as the compressive strength of concrete increases. Test results of 97 reinforced concrete members reported in the technical literatures are used to check the validity of the proposed equation. The comparison between the test results and the ratio calculated using the proposed equation indicated that the shear failure modes depended on the interaction between the amount of shear reinforcement and the compressive strength of concrete.

• Transactions of Materials Processing
• /
• v.21 no.5
• /
• pp.285-290
• /
• 2012

In spite of progress in predicting ductile failure, the development of a macroscopic yield criterion to describe damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in their plastic response due to twinning. Cazacu and Stewart(2009) developed an analytical yield criterion for porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that shows tension-compression asymmetry. The goal of the calculations in this paper is to investigate the effect of the tension-compression asymmetry on necking induced by void nucleation, evolution and consolidation. In order to investigate the effect of the tension-compression asymmetry of the matrix on necking and fracture initiation, three isotropic materials A, B, and C were examined with different ratios of tension-compression asymmetry. The various types of material had BCC, FCC, and HCP crystal structures, respectively. The ratio between tension and compression in plastic flow significantly influences the fracture shape produced by damage propagation as well as affecting the localized neck.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.304-307
• /
• 2004

Direct tensile tests were carried out for the tensile members of MMA-modified polymer concrete with different steel kinds and steel diameters and steel ratios to figure out the effect of tensile strength of polymer concrete. In the experiments, MMA-modified polymer concrete with $1000\;kgf/cm^2$ of compressive strength, steel with $5200\;kgf/cm^2$ of tensile strength, and the tensile members with 100 cm of constant length were used. Experimental results showed that, regardless of steel kinds, diameters and steel content, the strain energy exerted by concrete till the initial crack was $14-15\%$ of the total energy till the point of yield: The energy was much larger than the one of high-strength cement concrete. The behaviors of tensile members of MMA-modified polymer concrete were in relatively good agreement with the model suggested by Gupta-Maestrini (1990), which was idealized by the effective tensile stress-strain relationship of concrete and the load-strain relationship of members, while those showed a big difference from CEB-FIP model and ACI-224 equation suggested for the load-displacement relationship that was defined as the cross sectional stiffness of effective axis. Modified ACI-224 model code about the load-displacement relationship for the tensile members of MMA-modified polymer concrete and theoretical equation for the polymer concrete tensile stiffness of polymer concrete suggested through the results of this study are expected to be used in an accurate structural analysis and resign for the polymer concrete structural members.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2003.10a
• /
• pp.387-390
• /
• 2003

Direct tensile tests were carried out for the tensile members of steel-reinforced polymer concrete with different steel diameters and steel ratios to figure out the effect of tensile strength of polymer concrete. In the experiments, polymer concrete with $1000kgf/cm^2$ of compressive strength, steel with $5200kgf/cm^2$ of tensile strength, and the tensile members with 100 cm of constant length were used. Experimental results showed that, regardless of steel diameters and steel content, the strain energy exerted by concrete till the initial crack was 14-15% of the total energy till the point of yield: The energy was much larger than the one of high-strength cement concrete. The behaviors of tensile members of steel-reinforced polymer concrete were in relatively good agreement with the model suggested by Gupta-Maestrini (1990), which was idealized by the effective tensile stress-strain relationship of concrete and the load-strain relationship of members, while those showed a big difference from CEB-FIP model and ACI-224 equation suggested for the load-displacement relationship that was defined as the cross sectional stiffness of effective axis. Modified ACI-224 model code about the load-displacement relationship for the tensile members of steel-reinforced polymer concrete and theoretical equation for the polymer concrete tensile stiffness of polymer concrete suggested through the results of this study are expected to be used in an accurate structural analysis and design for the polymer concrete structural members.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.321-324
• /
• 2002

Hydraulic valve control the pressure and the How of fluid by the hydraulic oil transfered from pump but the ER fluid consists of solid particles of micrometer in size and insulating oil so in the general hydraulic valve. We invented ER-Valve using ER fluid as working fluid. The ER fluid, working fluid of ER-Valve is a functional fluid to represent the feature of fluid according to strength of electric field. In this research we made our own 4 types of plate type ER-Valve which has same surface but different width and length and then we conducted performance test. We measured flow rate and pressure drop of fluid which is flowing in the ER-Valve according to the electric field strength to conduct this test. We modeling ER-Valve relating to ER-Valve system and yield shear stress according to the strength of electric field. We used the pressure drop according to the strength of electric field by differential pressure gauge in the our own made ER-Valve. This test reviewed experimental the special changes of ER-Fluid in the steady flow condition.

• Advances in concrete construction
• /
• v.10 no.5
• /
• pp.431-441
• /
• 2020

For the purpose of improving the properties of UHPC as well as the economic efficiency in production of the material, Availability of river sands as fine aggregate instead of micro silica sand were investigated. Four different sizes of river sands were considered. Using river sand instead of micro silica sand increased the flowability, and decreased the yield stress and plastic viscosity in rheological properties, and the effect was higher with larger particle size of river sand. It was demonstrated by analyses based on the packing density. In the results of compressive strength and elastic modulus, even though river sand was not as good as micro silica sand, it could provide high strength of over 170 MPa and elastic modulus greater than 40 GPa. The difference in compressive strength depending on the size of river sand was explained with the concept of maximum paste thickness based on the packing density of aggregate. The flexural performance with river sand also presented relatively lower resistance than micro silica sand, and the reduction was greater with larger particle size of river sand. The flexural performance was proven to be also influenced by the difference in the fiber orientation distribution due to the size of river sand.

• Korean Journal of Materials Research
• /
• v.27 no.9
• /
• pp.477-483
• /
• 2017

This present study deals with the microstructure and tensile properties of 600 MPa-grade high strength and seismic resistant reinforcing steels. The high strength reinforcing steel (SD 600) was fabricated by Tempcore processing, while the seismic resistant reinforcing steel (SD 600S) was air-cooled after hot-rolling treatment. The microstructure analysis results showed that the SD 600 steel specimen consisted of a tempered martensite and ferrite-pearlite structure after Tempcore processing, while the SD 600S steel specimen had a fully ferrite-pearlite structure. The room-temperature tensile test results indicate that, because of the enhanced solid solution and precipitation strengthening caused by relatively higher contents of C, Mn, Si and V in the SD 600S steel specimen, this specimen, with fully ferrite-pearlite structure, had yield and tensile strengths higher than those of the SD 600 specimen. On the other hand, the hardness of the SD 600 and SD 600S steel specimens changed in different ways according to location, dependent on the microstructure, ferrite grain size, and volume fraction.

• Steel and Composite Structures
• /
• v.20 no.3
• /
• pp.571-597
• /
• 2016

A new unified design formula for calculating the composite compressive strength of the axially loaded circular concrete filled double steel tubular (CFDST) short and slender columns is presented in this paper. The formula is obtained from the analytic solution by using the limit equilibrium theory, the cylinder theory and the "Unified theory" under axial compression. Furthermore, the stability factor of CFDST slender columns is derived on the basis of the Perry-Robertson formula. This paper also reports the results of experiments and finite element analysis carried out on concrete filled double steel tubular columns, where the tested specimens include short and slender columns with different steel ratio and yield strength of inner tube; a new constitutive model for the concrete confined by both the outer and inner steel tube is proposed and incorporated in the finite element model developed. The comparisons among the finite element results, experimental results, and theoretical predictions show a good agreement in predicting the behavior and strength of the concrete filled steel tubular (CFST) columns with or without inner steel tubes. An important characteristic of the new formulas is that they provide a unified formulation for both the plain CFST and CFDST columns relating to the compressive strength or the stability bearing capacity and a set of design parameters.