• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.15-21
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• 2003

A series of triaxial compression tests were performed on samples of compacted granite soil in a modified triaxial cell that allowed separate control of pore air pressure ($U_a$) and pore water pressure ($U_w$) in order to examine the characteristics of pore pressure, volume change and stress-strain behavior during undrained loading conditions. Triaxial samples of unsaturated and saturated compacted granite soil, 50mm in diameter and 100mm in height, were prepared by compaction in a mould. These samples were tested at 3 different suction values (0.5, 1.0, 2.0 kgf/cm$^2$) for unsaturated compacted granite soil and at 3 different confining stresses (1.0, 2.0, 4.0 kgf/cm$^2$). Results showed that only effective cohesion increased with little variation of friction angle, according to matric suction.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.19-30
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• 2006

The purpose of this study was to examine the effect of foot orthotics on the overall comfort and muscle activity during running. The subjects were 10 members from the joggers' club which consisted of 2 women and 8 men. These individuals ran on the treadmill by 4.0m/s speed with and without the custom foot orthotics. The data concerning the overall comfort was collected by a questionairre that examined the overall comfort, heel cushioning, forefoot cushioning, medio-lateral control, arch height, heel cup fit, shoe heel width, forefoot width, and shoe length The MegaWin ver. 2.1(Mega Electronics lid, Ma. Finland) was used to gain electromyography signals of the muscle activity; Tibialis anterior, medial gastronemius, lateral gastronemius, vastus lateralis, vastus medialis, biceps femoris, and rectus femoris were measured. The results of the study were as follows. 1. During running the overall comfort was higher for the foot arthotic condition than the nonorthotic condition. Among the inquiries the overall comfort showed the biggest difference comparing the two conditions. and the shoe heel width showed the highest score for contort. 2 The muscle activity of the biceps femoris, and vastus lateralis in the stance period decreased. due to the foot orthotics. The muscle activity of the vastus medialis in the swing period also decreased and the muscle activity tibialis anterior in the stance and swing stance decreased as well During running, orthotics showed positive result in foot comfort. The foot comfort related to decreased stress, muscle activity, and foot arch strain. Overall comfort and the adequate decrease of muscle activity were associated with injury prevention and the best method to prevent injury semms to be the maintenance of foot comfort.

• Korean Journal of Organic Agriculture
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• v.22 no.4
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• pp.825-839
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• 2014

Antioxidant activity is important for reducing oxidative stress that causes various metabolic disorders. Metabolic disorders are highly related to loss of productivity in livestock. Therefore, development of effective antioxidant compounds originating from plants is important for organic agriculture. Phenolic compounds in edible plants are regarded as major components relevant to antioxidant activity. The present study investigated the changes in antioxidant activity and phenolic compound profiles of Aronia (Aronia meloncarpa) by fermentation using different strains of Leuconostoc mesenteroides. A total of 5 strains of L. mesenteroides were used as starter cultures and their ${\beta}$-glucosidase activities were measured. A total of 6 experiment runs were prepared, one for control (uninoculated) and the others (inoculated) for treatments. For biological activity, antioxidant and antibacterial activities were measured. For phenolic compound profiling, TLC and HPLC analysis were performed. The strains of KACC12313 and KACC12315 showed greater enzyme activity than others. Treatment with KCCM35046 showed strong and broad antibacterial activity against to Listeria monocytogenes. Treatments with KCCM35046 and KACC12315 showed the highest total polyphenol content. The highest antioxidant activity was found in KACC12315 treatment. No remarkable alteration was found in thin layer chromatography (TLC) analysis. In phenolic compound profiling analysis, KCCM35046 showed notable alteration in compound area ratio compared to others and also showed the highest caffeic acid content. In chlorogenic acid, treatments with KCCM35046 and KACC12315 showed great content than others. Treatment with KACC12315 showed the greatest content of trans-ferulic acid. As a result of relative performance indexing analysis, L. mesenteroides KCCM35046 and KACC12315 were selected as the best strain for the fermentation of Aronia.

• Journal of the Earthquake Engineering Society of Korea
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• v.25 no.3
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• pp.103-110
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• 2021

A shake table test is conducted for the three-story reinforced concrete building structure using 0.28 g, 0.5 g, 0.75 g, and 1.0 g of seismic input motions based on the Gyeongju earthquake. Computational efforts are made in parallel to explore the mechanical details in the structure. For engineering practice, the elastic modulus of concrete and rebar in the dynamic analysis is reduced to 38% and 50%, respectively, to calibrate the structure's natural frequencies. The engineering approach to the reduced modulus of elasticity is believed to be due to the inability to specify the flexibility of the actual boundary conditions. This aspect may lead to disadvantages of nonlinear dynamic analysis that can distort local stress and strain relationships. The initial elastic modulus can be applied directly without the so-called engineering adjustment with infinite element models with spring and spring-dashpot boundary conditions. This has the advantage of imposing the system flexibility of the structure on the sub-boundary conditions of springs and damping devices to control its sensitivity in a serial arrangement. This can reflect the flexibility of realistic boundary conditions and the effects of system damping (such as the gap between a concrete footing and shake table, loosening of steel anchors, etc.) in scalar quantities. However, these spring and dashpot coefficients can only be coordinated based on experimental results, making it challenging to select the coefficients in-prior to perform an experimental test.

• Geomechanics and Engineering
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• v.19 no.1
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• pp.37-47
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• 2019

The main objective of this study is to evaluate and compare the efficiency of ordinary Portland cement (OPC) in enhancing the unconfined compressive strength of soft soil alone and soft soil mixed with recycled tiles. The recycled tiles have been used to treat soft soil in a previous research by Al-Bared et al. (2019) and the results showed significant improvement, but the improved strength value was for samples treated with low cement content (2%). Hence, OPC is added alone in this research in various proportions and together with the optimum value of recycled tiles in order to investigate the improvement in the strength. The results of the compaction tests of the soft soil treated with recycled tiles and 2, 4, and 6% OPC revealed an increment in the maximum dry density and a decrement in the optimum moisture content. The optimum value of OPC was found to be 6%, at which the strength was the highest for both samples treated with OPC alone and samples treated with OPC and 20% recycled tiles. Under similar curing time, the strength of samples treated with recycled tiles and OPC was higher than the treated soil with the same percentage of OPC alone. The stress-strain curves showed ductile plastic behaviour for the untreated soft clay and brittle behaviour for almost all treated samples with OPC alone and OPC with recycled tiles. The microstructural tests indicated the formation of new cementitious products that were responsible for the improvement of the strength, such as calcium aluminium silicate hydrate. This research promotes recycled tiles as a green stabiliser for soil stabilisation capable of reducing the amount of OPC required for ground improvement. The replacement of OPC with recycled tiles resulted in higher strength compared to the control mix and this achievement may results in reducing both OPC in soil stabilisation and the disposal of recycled tiles into landfills.

• Food Engineering Progress
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• v.21 no.3
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• pp.233-241
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• 2017

Scaffolds of cell substrates are biophysical platforms for cell attachment, proliferation, and differentiation. They ultimately play a leading-edge role in the regeneration of tissues. Recent studies have shown the potential of bioactive scaffolds (i.e., osteo-inductive) through 3D printing. In this study, rice bran-derived biocomposite was fabricated for fused deposition modeling (FDM)-based 3D printing as a potential bone-graft analogue. Rice bran by-product was blended with poly caprolactone (PCL), a synthetic commercial biodegradable polymer. An extruder with extrusion process molding was adopted to manufacture the newly blended "green material." Processing conditions affected the performance of these blends. Bio-filament composite was characterized using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Mechanical characterization of bio-filament composite was carried out to determine stress-strain and compressive strength. Biological behaviors of bio-filament composites were also investigated by assessing cell cytotoxicity and water contact angle. EDX results of bio-filament composites indicated the presence of organic compounds. These bio-filament composites were found to have higher tensile strength than conventional PCL filament. They exhibited positive response in cytotoxicity. Biological analysis revealed better compatibility of r-PCL with rice bran. Such rice bran blended bio-filament composite was found to have higher elongation and strength compared to control PCL.

• Journal of Powder Materials
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• v.30 no.2
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• pp.146-155
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• 2023

The Ti-6Al-4V lattice structure is widely used in the aerospace industry owing to its high specific strength, specific stiffness, and energy absorption. The quality, performance, and surface roughness of the additively manufactured parts are significantly dependent on various process parameters. Therefore, it is important to study process parameter optimization for relative density and surface roughness control. Here, the part density and surface roughness are examined according to the hatching space, laser power, and scan rotation during laser-powder bed fusion (LPBF), and the optimal process parameters for LPBF are investigated. It has high density and low surface roughness in the specific process parameter ranges of hatching space (0.06-0.12 mm), laser power (225-325 W), and scan rotation (15°). In addition, to investigate the compressive behavior of the lattice structure, a finite element analysis is performed based on the homogenization method. Finite element analysis using the homogenization method indicates that the number of elements decreases from 437,710 to 27 and the analysis time decreases from 3,360 to 9 s. In addition, to verify the reliability of this method, stress-strain data from the compression test and analysis are compared.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.289-295
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• 2008

The purpose of this study was to examine the flexural behavior of reinforced concrete beams strengthened with CFRP strips. A total of 12 rectangular beams were tested. Test variables in this study were the shapes, bonded length and the number of longitudinal layers of CFRP strips. From the experimental study, flexural capacity of the beams strengthened with CFRP strips significantly increased compared to the reinforced concrete beam without a CFRP strip. Maximum increase of ultimate strength was found about 120% more than the control beam. In this test, most of the strengthened beams failed suddenly due to the debonding of CFRP strips. It is also observed that the debonding of the strip was initiated in the flexural zone of the beam and propagated rapidly to the end of the beam. The ultimate tensile strains of CFRP strips in this test were occurred at the level of 36% of rupture tensile strength of the CFRP strip, and an analytical approach to compute the flexural strength of reinforced beams strengthened with CFRP strips based on the effective stresses was conducted.

• Steel and Composite Structures
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• v.51 no.3
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• pp.243-260
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• 2024

Thirteen self-compacting recycled concrete filled aluminium tubular (SCRCFAT) columns were tested under concentric compression loads. The effects of the replacement ratio of the recycled concrete aggregate (RCA) and steel fibre (SF) reinforcement on the structural performance of the SCRCFAT columns were studied. A control specimen (C000) was cast with normal concrete without SF to be reference for comparison. Twelve columns were cast using RCA, six columns were cast using concrete incorporating 2% SF while the rest of columns were cast without SF. Failure mode, ductility, ultimate load capacity, axial deformation, ultimate strains, stress-strain response, and stiffness of the SCRCFAT columns were studied. The results showed that, the peak load of tested SCRCFAT columns incorporating 5-100 % RCA without SF reduced by 2.33-11.28 % compared to that of C000. Conversely, the peak load of tested SCRCFAT columns incorporating 5-100% RCA in addition to 2% SF increased by 21.1-40.25%, compared to C000. Consequently, the ultimate axial deformation (Δ) of column C100 (RCA=100% and SF 0%) increased by about 118.9 % compared to C000. The addition of 2% SF to the concrete mix decreased the axial deformation of SCRCFAT columns compared to those cast with 0% SF. Moreover, the stiffness of the columns cast without SF decreased as the RCA % increased. In contrast, the columns stiffness cast with 2% SF increased by 26.28-89.7 % over that of C000. Finally, a theoretical model was proposed to predict the ultimate loads tested SCRCFAT columns and the obtained theoretical results agreed well with the experimental results.

• Advances in concrete construction
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• v.17 no.5
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• pp.273-284
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• 2024

The steel-concrete composite system has been playing a vital role in the construction sector for the past two decades. By using steel and concrete together, we achieve strong load resistance with minimal deflection and bending stress. The study focuses on the numerical and analytical behaviour of concrete encased steel castellated beams and compared them with previous experiments. The study used five composite beams, including one control reinforced concrete beam (CC), one fully concrete encased steel beam (FCES), and three fully concrete encased castellated beams. The major variable is the opening configuration of the castellated beam, such as openings along the longitudinal axis, above the longitudinal axis, and below the longitudinal axis. The 150 mm × 250 mm cross section and 2000 mm in length of beams were used. Using the finite element software ANSYS, we conduct nonlinear finite element analysis for the entire beam and compare it with test data. The numerical load carrying capacity of concrete encased steel castellated beam with a hexagonal opening above the longitudinal axis (FCESCB H2) is 160 kN is closer to the experimental observation. Von Mises strain of FCESB is 0.004232, which is lower than CB and composite castellated beam. The ductility factor and energy absorption capacity of FCESB are 5.090 and 1688.47 kNm. It was observed that the configuration of the opening will influence the strength of the composite beam. Plastic moment methods were employed to estimate the ultimate load carrying capacity of the beam. In the analytical study the beams were assumed as perfectly plastic. The ultimate analytical load carrying capacity of FCESCB H2 is 21.87% higher than FCESB. It found that performing FCESCB H2 is superior to the entire specimen.