• Corrosion Science and Technology
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• v.23 no.2
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• pp.113-120
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• 2024

An attempt was made to apply digital image correlation (DIC) strain analysis to in-situ scanning electron microscopy (SEM) observations of bending deformation to quantify local strain distribution inside a ZnMgAl-alloy coating in deformation. Interstitial-free steel sheets were hot-dipped in a Zn-3Mg-6Al (mass%) alloy melt at 400 ℃ for 2 s. The specimens were deformed using a miniature-sized 4-point bending test machine inside the SEM chamber. The observed in situ SEM images were used for DIC strain analysis. The hot-dip ZnMgAl-alloy coating exhibited a solidification microstructure composed of a three-phase eutectic of fine Al (fcc), Zn (hcp), and Zn2Mg phases surrounding the primary solidified Al phases. The relatively coarsened Zn₂Mg phases were locally observed inside the ZnMgAl-alloy coating. The DIC strain analysis revealed that the strain was localized in the primary solidified Al phases and fine eutectic microstructure around the Zn₂Mg phase. The results indicated high deformability of the multi-phase microstructure of the ZnMgAl-alloy coating.

• Composites Research
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• v.14 no.1
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• pp.8-14
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• 2001

A simplified method for determining the three mode(I, II, III) components of the strain energy release rate of free-edge delaminations in composite laminates is proposed. The interlaminar stresses are evaluated using the interface moment and the interface shear forces which are obtained from the equilibrium equations at the interface between the adjacent layers. Deformation of an edge-delaminated laminate is analysed by using a generalized quasi-three dimensional classical laminated plate theory. The analysis provides closed-form expression for the three components of the strain energy release rate. The analyses are performed for composite laminates subjected to uniaxial tension, with free-edge delaminations located symmetrically and asymmetrically with respect to the laminate midplane. The analysis results agreed with a finite element solution using the virtual crack closure technique.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.5
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• pp.377-381
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• 2006

A study was carried out to determine a suitable light intensity and inoculum size for the growth of Rhodopseudomonas palustris strain B1. The pollution reduction of sago effluent using free and immobilised R. palustris cells was also evaluated. The growth rate in glutamatemalate medium was highest at 4 klux compared to 2.5 and 3 klux. The optimal inoculum size was 10% (v/v). Both the COD and BOD of the sago effluent were reduced by 67% after three days of treatment. The difference in biomass production or BOD and COD removal with higher inoculum sizes of 15 and 20% was minimal. This could be attributed to limited nutrient availability in the substrate. The use of immobilised cells of R. palustris reduced the pollution load 10% less compared to pollution reduction by free cells. Hence, there was no significant difference in using free or immobilised cells for the treatment of sago effluent.

• Korean Journal of Metals and Materials
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• v.48 no.1
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• pp.77-84
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• 2010

Annealing characteristics of an oxygen free copper (OFC) processed by differential speed rolling (DSR) were investigated in detail. An OFC sample with a thickness of hum was rolled to 35% reduction at ambient temperature without lubrication, varying the differential speed ratio from 1.0:1 to 2.2:1, and then annealed for 0.5h at various temperatures from 100 to $400^{\circ}C$. Different recrystallization behavior was observed depending on the differential speed ratio, especially in the case of annealing at $200^{\circ}C$ Complete recrystallization occurred in the specimens annealed at temperatures above $250^{\circ}C$ regardless of the differential ratios. The hardness distribution in the thickness direction of the rolled OFC sheets varied depending on the differential speed ratios. These annealing characteristics were explained by the magnitude of shear strain introduced during rolling.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.408-414
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• 2021

This study analyzes the phase transition behavior and electrical properties of lead-free (1-x)K_0.5Na_0.5NbO₃-xBaZrO₃ (KNN-100xBZ) piezoelectric ceramics. The stabilized crystal structures in BaZrO₃-modified KNN ceramics is clarified to be pseudocubic. The polymorphic phase transition from the orthorhombic to pseudocubic phases can be observed with KNN-6BZ ceramics considering the optimized piezoelectric constant (d₃₃). Electromechanical strain behaviors are discussed. Accordingly, the enhancement of strain value at x = 0.08 (composition) may originate from the coexistence of ferroelectric domains and polar nanoregions. A schematic of domains for KNN, KNN-8BZ, and KNN-15BZ ceramics has been proposed to describe the relationship between the stabilized relaxor and changes in electrical properties.

• Geomechanics and Engineering
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• v.28 no.1
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• pp.25-33
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• 2022

The energy transferred on drill rods by dynamic impact mainly determines the penetration depth for in-situ tests. In this study, the dynamic response and transferred energy of drill rods are determined from the frequency of the stress waves. AW-type drill rods of lengths 1 to 3 m are prepared, and strain gauges and an accelerometer are installed at the head and tip of the connected rods. The drill rods are hung on strings, allowing free vibration, and then impacted by a pendulum hammer with fixed potential energy. Increasing the rod length L increases the wave roundtrip time (2L/c, where c is the wave velocity), and hence the transferred energy at the rod head. At the rod tip, the first velocity peak is higher than the first force peak because a large and tensile stress wave is reflected, and the transferred energy converges to zero. The resonant frequency increases with rod length in the waveforms measured by the strain gauges, and fluctuates in the waveforms measured by the accelerometer. In addition, the dynamic response and transferred energy are perturbed when the cutoff frequency is lower than 2 kHz. This study implies that the resonant frequency should be considered for the interpretation of transferred energy on drill rods.

• Journal of the Korean Professional Engineers Association
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• v.24 no.1
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• pp.33-56
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• 1991

• Journal of Microbiology
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• v.42 no.4
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• pp.305-314
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• 2004

An exopolysaccharide-producing microalgal dinoflagellate was isolated from a red-tide bloom and des­ignated strain KG03. A bacteria-free culture of strain KG03 was achieved using a modified wash with phototaxis and antibiotic treatment. Combined treatment with neomycin and cephalosporin was the most effective for eliminating the bacteria associated with the microalgae. Strain KG03 was identified as Gyrodinium impudicum by analyzing the ITS regions of the 5.8S rDNA, 18S rDNA, morphological phenotype and fatty acid composition. The exopolysaccharide production and cell growth in a 300-ml photobioreactor were increased 2.7- and 2.4-fold, respectively, compared with that in a flask culture at the first isolation step.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.697-700
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• 2003

Lactococcus lactis NK24, Lactobacillus plantarum NK181, and strain HW161 were previously isolated from Jeot-gal. For antioxidative activity, the culture supernatants of there probiotic strains were shown to be 78, 77, and 81% by DPPH method. Also, the peroxidation of linoleic acid of them was investigated and they were about 3.5, 4.6, and 2.0%. And cholesterol-lowering activity of Jeot-gal probiotic strains were about 40, 33, and 60%, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.355-360
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• 1996

When the operational strains of a structure can not be directly measured in order to predict the life of the structure due to the problem of the attachment, those must be obtained indirectly. Since the displacement and the strain are interrelated, the strain can be predicted from the measured displacement and displacement-strain transformation matrix. The transformation matrix is dependent on the boundary condition, unfortunately, and it is also difficult to know exactly that of the operational system. In this study, for the structure with arbitrary boundary condition under the operation, the approximate method is proposed in order to predict the operational strains using the transformation matrix obtained by using free boundary conditions. And the method is applied to predict the strains of leads of surface mount component under the vibration of the printed circuit board.