• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2324-2331
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• 2024

The current study investigated Saudi Arabian oil fly ash impacts on Egyptian clay bricks' structural and radiation shielding properties. To produce the required bricks, crushed clay minerals from the Hafafit area were mixed with 0, 10, 20, 30, and 40 % wt.% Saudi Arabian oil fly ash and pressed at a pressure rate of 68.55 MPa. Identification of the minerals in the chosen clay was achieved via X-ray diffraction. Additionally, the material's morphology and chemical composition were determined through scanning electron microscope and energy-dispersive X-ray. The fabricated bricks' density was reduced by 36.3 % through increasing the concentration of fly ash from 0 to 40 wt%. Then, the fly ash addition's influence on the fabricated clay bricks' γ-ray shielding properties was investigated by Monte Carlo simulation, which found a reduction in the fabricated bricks' linear attenuation coefficient (LAC) by 41.2, 36.0, 33.8, and 33.8 % at the 0.059, 0.103, 0.662, and 1.252 MeV γ-ray energies, respectively. The LAC reduction caused an increase in the fabricated bricks' half-value thickness, transmission factor, and the equivalent thickness of the lead. Moreover, the thicker fabricated sample thicknesses were found to have high γ-ray shielding capacity and can thus be used in radiation shielding applications.

• Coupled systems mechanics
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• v.8 no.4
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• pp.299-313
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• 2019

The paper represents computer modeling of the deformed state of physically nonlinear transversally isotropic bodies with hole. In order to describe the anisotropy of the mechanical properties of transversally-isotropic materials a structurally phenomenological model has been used. This model allows representing the initial material in the form of the coupled isotropic materials: the basic material (binder) considered from the positions of continuum mechanics and the fiber material oriented along the anisotropy direction of the original material. It is assumed that the fibers perceive only the axial tensile-compression forces and are deformed together with the base material. To solve the problems of the theory of plasticity, simplified theories of small elastoplastic deformation have been used for a transversely-isotropic body, developed by B.E. Pobedrya. A simplified theory allows applying the theory of small elastoplastic deformations to solve specific applied problems, since in this case the fibrous medium is replaced by an equivalent transversely isotropic medium with effective mechanical parameters. The essence of simplification is that with simple stretching of composite in direction of the transversal isotropy axis and in direction perpendicular to it, plastic deformations do not arise. As a result, the intensity of stresses and deformations both along the principal axis of the transversal isotropy and along the perpendicular plane of isotropy is determined separately. The representation of the fibrous composite in the form of a homogeneous anisotropic material with effective mechanical parameters allows for a sufficiently accurate calculation of stresses and strains. The calculation is carried out under different loading conditions, keeping in mind that both sizes characterizing the fibrous material fiber thickness and the gap between the fibers-are several orders smaller than the radius of the hole. Based on the simplified theory and the finite element method, a computer model of nonlinear deformation of fibrous composites is constructed. For carrying out computational experiments, a specialized software package was developed. The effect of hole configuration on the distribution of deformation and stress fields in the vicinity of concentrators was investigated.

• Journal of the Korean Chemical Society
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• v.43 no.1
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• pp.23-29
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• 1999

The Al oxide layer formed in 1M $H_2SO_4$ solution and the influence of applied frequency for electrodeposition of Mn on Al oxide layer were characterized using by impedance spectroscopy. Mn compounds were electrodeposited at the base of pores during deposition with applied low frequency voltage. For the Mn deposited oxide layer at 6OHz and 5Hz in 1 g/L $KMnO_4$ solution, in equivalent circuit for interpretation, the resistance ($R_2$) and capacitance ($C_2$) were considered to be due to deposition of Mn on base of pore. The electrochemical behavior of barrier layer and porous oxide layer on Al have been characterized by capacitance ($C_b$) and Young capacitance ($C_Y$) in equivalent circuit model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.41-50
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• 2012

Improvement of steel material quality made fatigue problems more critical than failure of the material itself. In many cases, cracks on the welded parts of steel deck bridges are reported against the failure of steel materials. And the cracks are caused by alternate stress on the welded parts due to live loads on the bridge. The range of alternate stress on the welded part is related to property of the sections which compose othortropic steel deck. Othortropic steel deck is mainly composed of deck plate, ribs and floor beams, wearing surface, etc. In this paper, a methology to estimate the alternate stress for pthortropic steel deck using Pelikan-Esslinger method and signed Von-Mises equivalent stress is proposed first. Parametric study served references for fatigue stresses when designing or repairing othortropic steel deck bridges, by analyzing relationship between alternate stress range and properties of steel deck members.

• Journal of the Korea Convergence Society
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• v.12 no.1
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• pp.105-110
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• 2021

Radiation shielding of affinity material, which is widely used in medical institutions, is made in sheet form and is mainly applied to apron. Shielding performance is presented based on lead equivalent, and is presented as 0.25-0.50mmPb. In the case of shielding materials where lead is used as the main material, the shielding performance can be adjusted by thickness due to the excellent machinability of lead. However, eco-friendly shielding sheets are difficult to control shielding performance based on thickness criteria as shielding performance varies depending on the content of shielding materials, the properties of polymeric materials that are base materials, and the technical differences in the process. In this study, shielding sheets were manufactured based on thickness to solve these problems and the shielding performance was compared in this study. As a result, it was shown that the laminated structure shielding sheet was more effective.

• Composites Research
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• v.24 no.4
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• pp.29-35
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• 2011

The characteristic length method used to determine a laminate's strength generally requires the test for un-notched and notched laminates and finite element analysis together. In this paper, the methods used to predict the stress distribution and tensile characteristic length of open-hole laminates using the stress concentration factor and equivalent material properties are proposed. These methods do not require data on the failure load of open-hole laminates or finite element analysis. Once the stress and characteristic length have been determined, the failure load of the open-hole laminate can be calculated. The proposed method considers the effect of the material properties as a parameter and therefore can be applied to a variety of materials. The stress distribution is verified by comparing with a finite element analysis and test results. The predicted failure load shows a maximum deviation of 8% from the test results.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.3
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• pp.383-391
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• 2014

This study was conducted to ascertain the antioxidant properties of Hamcho (Salicornia herbacea L.) and as well as manufacture pettitoes using Hamcho as a natural antioxidant material for diverse applications. The DPPH radical scavenging activities of 25, 50, 100 mg/mL in methanol extracts from Salicornia herbacea L. increased significantly (p<0.05) to 12.8%, 21.6% and 39.1%, respectively. The total phenolic content was $38.58{\pm}4.25{\mu}M$ as tannic acid equivalent for 100 mg/mL of methanol extracts from Hamcho. FRAP value was $448.58{\pm}14.01{\mu}M$ as ascorbic acid equivalent in reducing power. To apply Hamcho to food as a natural antioxidant, pettitoes were prepared with added Hamcho. To manufacture pettitoes added with Hamcho, general quality characteristics of pettitoes added with 0%, 2%, 4% and 6% based on 100 g of pettitoes were determined. In conclusion, mineral components increased according to the added amount of Salicornia herbacea L. Crude protein showed the highest value with 2% added Hamcho. Overall, the addition of Hamcho led to hardening of the meat texture. As a result of measuring color in terms of brightness, redness, and yellowness with chromaticity, the L value (brightness) increased with added amount of Hamcho. There was no significant difference in redness or yellowness. As a result of the sensory evaluation of pettitoes according to addition of Hamcho, the group with 4% added Hamcho showed enhanced overall preference with improved flavor, taste and textural properties.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.284-295
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• 2012

Abrasiveness of rock plays an important role on the wear of rock cutting tools. In this study, Cerchar abrasiveness tests were carried out to assess the abrasiveness of 19 different Korean rocks. Cerchar abrasiveness test is widely used to assess the abrasiveness of rock because of its simplicity and inexpensive cost. This study examines the relationship between Cerchar Abrasiveness Index (CAI) and mechanical properties (uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio, porosity, shore hardness of rock), and the effect of quartz content, equivalent quartz content, which was obtained from XRD analysis. As a result of test, CAI was more influenced by petrographical properties than by the bonding strength of the matrix material of rock. CAI prediction model which consisted of UCS and EQC was proposed. CAI decreased linearly with the hardness of the steel pin. Numerical analysis was performed using Autodyn-3D for simulating the Cerchar abrasiveness test. In the simulations, most of pin wear occurred during the initial scratching distance, and CAI increased with the increase of normal loading.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.184-192
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• 2019

Compared to 31-mode rings, 33-mode rings are highly utilized as wide bandwidth underwater acoustic transducers because the electro-mechanical coupling and piezoelectric constant d are high. On the other hand, the 31-mode ring is an axial symmetry structure, so it is possible to model it as a simple two-dimensional asymmetrical model for numerical analysis, but the 33-mode ring requires a three-dimensional numerical analysis. That is, a lot of computing resources and computation time are required. In this study, the effective material properties of an equivalent 31-mode ring were derived to simulate the electro-mechano-acoustical responses of the 33-mode ring transducer. Using the effective material properties derived from this study, a numerical analysis of rings in vacuum, air backed rings in water, and FFR (Free Flooded Ring) transducers were performed to compare the responses of 33-mode rings.

• Advances in concrete construction
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• v.9 no.1
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• pp.103-113
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• 2020

This paper deal with the critical fluid velocity response of nanocomposite pipe conveying fluid based on numerical method. The pressure of fluid is obtained based on perturbation method. The motion equations are derived based on classical shell theory, energy method and Hamilton's principle. The shell is reinforced by nanoparticles and the distribution of them are functionally graded (FG). The mixture rule is applied for obtaining the equivalent material properties of the structure. Differential quadrature method (DQM) is utilized for solution of the motion equations in order to obtain the critical fluid velocity. The effects of different parameters such asCNT nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios and internal fluid are presented on the critical fluid velocity response structure. The results show that with increasing the CNT nanoparticles, the critical fluid velocity is increased. In addition, FGX distribution of nanoparticles is the best choice for reinforcement.