• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.4
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• pp.343-350
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• 2013

Instant krill gruel was produced using peeled Antarctic krill Euphausia superba as a high nutritional ingredient and the food quality was investigated. The food quality of krill gruel was examined by measuring proximate composition, cholesterol, calorie, Hunter color value, total amino acids, fatty acids, fluoride, viscoelastic properties, and by sensory evaluation. The krill gruel had a moisture content of 87% and a pH of 6.65. The krill gruel contained 51 kcal/100 g, and 0.1% fat and 3.5 mg/100 g cholesterol. Its fatty acid composition exhibited high levels of unsaturated fatty acids. The levels of oleic acid and linolenic acid were high, and n-3, n-6, and n-9 fatty acid contents ranged from 1% to 6%. The total amino acid content was 2132 mg/100 g, and the levels of glutamic acid, aspartic acid, leucine, alanine, and arginine were particularly high. Essential amino acids accounted for over 30% of the total amino acids. Fluoride level in the krill gruel was 3.07 mg/kg. The viscoelastic properties of the krill gruel were determined as 6.28 Pa at shear stress of 2.51 Pa. In the recovery test, the elastic restoring force after deformation was low.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.117-127
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• 2011

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

• Journal of the Korean Wood Science and Technology
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• v.42 no.4
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• pp.367-375
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• 2014

A simplified material model, which was efficiently implemented in a three-dimensional finite solid element (3D FE) analysis for wood was developed. The bi-linear elasto-plastic anisotropic material theory was adopted to describe constitutive relations of wood in three major directions including longitudinal, radial and tangential direction. The assumption of transverse isotropy was made to reduce the requisite 27 material constants to 6 independent constants including elastic moduli, yield stresses and Poisson's ratios in the parallel, and perpendicular to grain directions. The results of Douglas fir compression tests in the three directions were compared to the 3D FE simulation incorporated with the wood material model developed in this study. Successful agreements of the results were found in the load-deformation curves and the permanent deformations. Future works and difficulties expected in the advanced application of the model were discussed.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.77-84
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• 2012

The engineering characteristics of natural sediments containing diatom microfossils have been investigated for their abnormal deformation and strength behavior for a few decades. The presence of disk or hollow shape diatoms causes low compressibility, high hydraulic conductivity, and high shear strength of sediments. Some of these unusual differences show the characteristic of diatom owing to the interlocking of large interparticle porosity and angular particles. This phenomenon implies the possible use of diatom as modification materials to change the engineering performance of soil mixtures. This paper describes the engineering characteristics of diatom-kaolin mixture to investigate the engineering properties of diatom modified soils using conventional geotechnical tests and elastic and electromagnetic wave propagation tests. Experimental test results show the performance improvement by increasing diatom contents and the performance degradation by the breakage of interlocking between diatom particles under high effective stress.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.345-356
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• 2008

In the previous study, direct inelastic strut-and-tie model (DISTM) was developed to perform inelastic design of reinforced concrete members by using linear analysis for their secant stiffness. In the present study, for convenience in design practice, the DISTM was further simplified so that inelastic design of reinforced concrete members can be performed by a run of linear analysis, without using iterative calculations. In the simplified direct inelastic strut-and-tie model (S-DISTM), a reinforced concrete member is idealized with compression strut of concrete and tension tie of reinforcing bars. For the strut and tie elements, elastic stiffness or secant stiffness is used according to the design strategy intended by engineer. To define the failure criteria of the strut and tie elements, concrete crushing and reinforcing bar fracture were considered. The proposed method was applied to inelastic design of various reinforced concrete members including deep beam, coupling beam, and shear wall. The design results were compared with the properties and the deformation capacities of the test specimens.

• Composites Research
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• v.17 no.4
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• pp.61-67
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• 2004

Nondestructive damage sensitivity on single-basalt fiber/epoxy composites was evaluated by micromechanical technique and acoustic emission (AE). Piezoelectric lead-zirconate-titanate (PZT), polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer were used as AE sensor, respectively. In single-fiber composite, the damage sensing with different sensor types were compared to each other. Piezoelectric PVDF polymer sensor was embedded in and attached on the composite, whereas PZT sensor was only attached on the surface of specimen. In case of embedded polymer sensors, responding sensitivity was higher than that of the attached case. It can be due to full constraint inside specimen to transfer elastic wave coming from micro-deformation. For both the attached and the embedded cases, the sensitivity of P(VDF-TrFE) sensor was almost same as that of conventional PVDF sensor.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1489-1498
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• 2013

The monolithically coupled finite element analysis for a deformable unsaturated soil slope is performed to investigate the effect of antecedent rainfall which is assumed by initial conditions varying degree of saturation (36, 51, 77%) in finite element analysis. The distributions of matric suction and deformation on slope surface obtained from numerical simulation show the instability of antecedent rainfall-induced unsaturated soil slope. Moreover, the numerical analysis using Drucker-Prager model can be checked if a soil slope has reached failure (trial failure criterion $f^{tr}$ >0, plastic behavior) or not (trial failure criterion $f^{tr}$ < 0, elastic behavior). It is found that displacement of slope surface layer increases and the matric suction on soil slope decreases with an increase of initial degree of saturation by antecedent rainfall. Especially, the matric suction of the soil slope in dry condition (S=36%) rapidly decreases rather than that in wet condition (S=51%) at the same rainfall duration. The results of the trial failure criterion ($f^{tr}$ > 0) show slope instability in the toe region and surface of the slopes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.777-785
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• 2000

The low-cycle fatigue behaviors of cast AI-Si alloy and composite with reinforcement of SIC particles were compared with those of extruded unreinforced matrix alloy and composite in order to investigate the influence of cast and extrusion processes on the cyclic deformation and fatigue life. Generally, both cast and extruded composites including the unreinforced alloy exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. However, cast composite under a low applied cyclic strain showing no observable plastic strain exhibited cyclic softening behavior due to the cast porosities. The elastic modulus and yield strength of the cast composite were found to be quite comparable to those of the extruded composite, however, the extrusion process considerably improved the ductility and fracture strength of the composite by effectively eliminating the cast porosities. Low-cycle fatigue lives of the cast alloy and composite were shorter than those of the extruded counterparts. Large difference in life between cast and extruded composites was attributed to the higher influence of the cast porosities on the fatigue life of the composite than that of the unreinforced alloy material. A fatigue damage parameter using strain energy density effectively represented the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced alloy.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.1-7
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• 2007

As fiber reinforced composite materials are widely used in aircraft, space structures and robot arms, the study on non-destructive testing methods has become an important research area for improving their reliability and safety. AE (acoustic emission) can evaluate the defects by detecting the emitting strain energy when elastic waves are generated by the initiation and growth of crack, plastic deformation, fiber breakage, matrix cleavage, or delamination. In the paper, AE signals generated under uniaxial tension were measured and analyzed using the $8{\times}8$ matrix piezo electric sensor. The electronic circuit to control the transmitting distance of AE signals was designed and constructed. The optical data storage system was also designed to store the AE signal of 64channels using LED (light emitting diode) elements. From the tests, it was shown that the source location and propagation path of AE signals in composite materials could be detected effectively by the $8{\times}8$ matrix piezo electric sensor.

• Steel and Composite Structures
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• v.36 no.3
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• pp.355-367
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• 2020

The current work, present dynamic analysis of the FG-sandwich plate seated on elastic foundation with various kinds of support using refined shear deformation theory. The present analytical model is simplified which the unknowns number are reduced. The zero-shear stresses at the free surfaces of the FG-sandwich plate are ensured without introducing any correction factors. The four equations of motion are determined via Hamilton's principle and solved by Galerkin's approach for FG-sandwich plate with three kinds of the support. The proposed analytical model is verified by comparing the results with those obtained by other theories existing in the literature. The parametric studies are presented to detect the various parameters influencing the fundamental frequencies of the symmetric and non-symmetric FG-sandwich plate with various boundary conditions.