• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.115-120
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• 2015

Explicit expressions are derived for the effective reflection coefficients of obliquely incident light on a multilayered substrate coated with two uniaxially anisotropic films. Based on these reflection coefficients, ellipsometric constants are obtained as function of the tilt and azimuthal angles of the optical axes of the uniaxial films. Explicit expressions are provided, which can be used to separate the effects of surface anisotropy for anisotropic film from that of its bulk anisotropy, so that these expressions may be utilized in characterizing the surface anisotropy of alignment layers.

• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.13-17
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• 2022

The mechanical properties of REBCO coated conductor (CC) tapes under uniaxial tension are mainly determined by the thick layer Components like the substrate and the stabilizer. Depending on the applications of the CC tapes, it is also needed to externally reinforce thin metallic foils to one side or both sides of the CC tapes. This study investigated the effect of additional stabilizer layers or lamination on the electrical resistivity and electromechanical properties in RCE-DR processed GdBCO CC tapes with different structures. The strain/stress tolerance of I_c in differently processed 12 mm-wide REBCO CC tapes under uniaxial tension at 77 K and self-field could be determined by the loading-unloading scheme. As a result, Sn-Cu stabilized CC tape showed a significant decrease in mechanical properties due to its soft but thick stabilizing layer. However, similar electromechanical properties have been observed on both Sn-Cu and Sn-stabilized CC tapes, the I_c degradation behavior was independent of whether the CC tape has an external reinforcement or different stabilizing layers.

• Computers and Concrete
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• v.33 no.6
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• pp.659-670
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• 2024

The mechanical behaviour of layered concrete samples containing an internal crack was numerically studied by modelling the geo-mechanical specimens in the particle flow code in two dimensions (PFC2D). The numerical modelling software was calibrated with the experimental results of the Brazilian tensile strengths gained from the laboratory disc-type specimens. Then, the samples with the bedding layers and internal notch were numerically simulated with PFC2D under uniaxial compressive loading. In each specimen, the layers' thickness was 10 mm but the layer's inclination angle was changed to 0°, 30°, 60°, 90°, 120° and 150°. Of course, the layers'interfaces are considered to have very low strengths. The internal notch was kept at 3 cm in length however, its inclination angle was changed to 0°, 40°, 60° and 90°. Therefore, a total, of 24 numerical models were made to study the failure mechanism of the layered concrete samples. Considering these results, it has been concluded that the inclination angles of both internal crack and bedding layers affect the failure mechanism and uniaxial compressive strength of the concrete.

• International Journal of Highway Engineering
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• v.17 no.5
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• pp.25-31
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• 2015

PURPOSES: The objective of this study is to analyze the relationship between the FWD back-calculated modulus and dynamic modulus of asphalt layers for existing asphalt pavements. METHODS: To evaluate the dynamic modulus of the asphalt mixture in the existing and new asphalt layers, the uniaxial direct tension test was conducted on small asphalt specimens obtained from the existing asphalt-covered pavements. A dynamic modulus master curve was estimated by using the uniaxial direct tension test for each asphalt layer. The falling weight deflectometer (FWD) testing was conducted on the test sections, and the modulus values of pavement layers were back-calculated using the genetic algorithm and the finite element method based back-calculation program. The relationship between measured and back-calculated asphalt layer moduli was examined in this study. The normalized dynamic modulus was adopted to predict the stiffness characteristics of asphalt layers more accurately. RESULTS: From this study, we can conclude that there is no close relationship between dynamic modulus of first layer and back-calculated asphalt modulus. The dynamic moduli of second and third asphalt layers have some relation with asphalt stiffness. Test results also showed that the normalized dynamic modulus of the asphalt mixture is closely related to the FWD back-calculated modulus with 0.73 of R square value. CONCLUSIONS: The back-calculated modulus of asphalt layer can be used as an indicator of the stiffness characteristics of asphalt layers in the asphalt-covered pavements.

• Journal of the Korean Society of Safety
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• v.16 no.1
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• pp.53-58
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• 2001

Constructions on the soft clay layer of low strength and high compression bring out many problems. Recent studies show that strength of the soft clay layer could be substantially improved by mixing quicklime. For the purpose, a series of uniaxial compression tests were performed, using quicklime, in order to analyze strength characteristics. The major test results are summarized following : When water content is 90%, the strength is observed to precipitously increase between 3～14 days, then, the extent slowly increase in relative terms. When water content is 130%, the strength is observed to precipitously increase up to 28 days. When the strength of water content 90% is compared to that of water content 130%, the initial strength of the former is higher than that of the latter. The analyses show that the improvement of soft clay layers can be realized by the mixture of both quicklime and sand, and by the mixture of quicklime only.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.69-75
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• 1995

The deformation behavior of stainless steel-clad aluminum sheet metals under uniaxial tension has been investigated. The differences in mechanical properties such as elastic modulus, flow stress and plastic strain ratio, of component layers of the composite sheet gave rise to warping of the tensile specimens. The warping has been analyzed by FEM and the total force and momentum equilibria. The analyzed radii of curvature of the warped specimens were smaller than the measured data possibly due to elastic recovery during unloading. The differences in mechanical properties may also give rise to transverse stresses in the component layers. The transverse stresses have been analyzed on the assumption of isostrain and by the FEM in which the warping has been taken into account. The transverse stresses calculated by the FEM were lower than those by the isostrain hypothesis due to stress relaxation by the warping and turned out to be negligible compared with the longitudinal stresses. Consequently, the flow stresses of the composite sheets follow the rule of mixtures.

• Macromolecular Research
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• v.14 no.3
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• pp.318-323
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• 2006

We investigated the rheological behaviors and orientation of three different types of layered silicate composite systems under external flow: microcomposite, intercalated and exfoliated nanocomposites. Rheological measurements under shear and uniaxial extensional flows, two-dimensional, small-angle X-ray scattering and transmission electron microscopy were conducted to investigate the properties, as well as nano- and micro-structural changes, of polymer/layered silicate nanocomposites. The preferred orientation of the silicate layers to the flow direction was observed under uniaxial extensional flow for both intercalated and exfoliated systems, while the strain hardening behavior was observed only in the exfoliated systems. The degree of compatibility between the polymer matrix and clay determined the microstructure of polymer/clay composites, strain hardening behavior and spatial orientation of the clays under extensional flow.

• Advances in concrete construction
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• v.9 no.6
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• pp.529-535
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• 2020

The current study investigated experimentally the effectiveness of Carbon Fiber Reinforced Polymer (CFRP) in confining concrete cylinders after being subjected to high temperature. Parameters examined were: (a) the exposing temperatures (20, 100, 200, 400 600 and 700℃) and (b) the number of CFRP layers (1 and 3 layers). A uniaxial compressive testing was carried out on 36 concrete cylinders with dimensions of 150 mm×300 mm. The results obtained show that the compressive strength reduced with the increased of temperature compared to that measured at 20℃. In particular, the reduction in the compressive strength was more observed when the temperature exceeded 400℃. Further, the concrete cylinders confined with one and three layers of CFRP significantly increased the compressive strength compared to the counterpart unconfined specimen tested at the same temperature. Also, the average percentages of the increase in the compressive strength were approximately 112% and 158% when applying 1 and 3 layers of CFRP, respectively, compared to the counterpart unstrengthened specimen tested at the same temperature.

• Proceedings of the Korean Magnestics Society Conference
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• 2014.11a
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• pp.153-153
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• 2014

• Korean Journal of Optics and Photonics
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• v.26 no.5
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• pp.275-282
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• 2015

The effective reflection coefficients for light obliquely incident upon a substrate coated with uniaxially anisotropic films and with isotropic films are derived. Multiple reflections inside anisotropic films, as well as those inside isotropic films, are properly treated. These expressions, together with the related ellipsometric expressions, can be used to find the nonuniform distribution of an uniaxially anisotropic film perpendicular to the film's surface, by approximating it as consisting of uniaxially anisotropic uniform layers and applying the conventional modeling technique for spectroscopic ellipsometry.