• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.46-51
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• 1990

Laser plasma was generated by a 1GW iodine photodissociation laser ($\lambda$=1.315$\mu\textrm{m}$, E=12.7J) whose output beam was focused on a molybdenum target surface. The experiment was conducted in a vacuum chamber under 1D-sTorr and several tens of laser shooting were necessary for sufficient exposure for the PBS resist of 111m thickness. Aluminium was coated on the top of the resist by 0.1$\mu\textrm{m}$ thickness which acts as an X-ray filter to cut off the visible and the ultraviolet lights. A bio-specimen was put directly on the aluminium coated resist and located at a distance of 3 cm from the X-ray source. The replicas of a steel mesh, spider's web. and a red blood cell were obtained by this technique and were observed by Nomarski microscope and SEM. The limitation of its resolution is determined by the X-ray source size and Fresnel diffraction effect, and its theoretical prediction is well matched with the experimental results. In this experiment, a resolution better than 0.1$\mu\textrm{m}$ could be obtained. ained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.54-62
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• 2019

In this paper, a stress-strain model for high-strength confined concrete is proposed using compressive fracture energy. In the compression test performed by author in Reference [6], an acrylic bar with strain gauges was embedded in the center of the specimen to measure the local strain distribution. It was found from the test that the local strain measurement by this acrylic rod is very effective. The local fracture zone length was defined based on the local strain distribution measured by the acrylic rod. Specifically, it was defined as the length where the local strain increases more than twice of the strain corresponding to maximum stress. In addition, the stress-strain relationship of confined concrete with compressive fracture energy is proposed on the assumption that the amount of energy absorbed by the compressive members subjected to the given lateral confining pressure is constant regardless of the aspect ratio and size. The proposed model predicts even results from other researchers accurately.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.39-54
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• 2009

Large scale direct shear tests were carried out to analyze the shear behavior of crushed rocks at local representative quarries. Shear strength for each specimen was derived and the effects on shear behavior induced by the variation of factors such as particle size, water immersion, density, uniformity coefficient, and particle breakage were evaluated and quantitatively compared with previous studies. The opportunity was also taken to identify stress-dilatancy relation of crushed rocks following the energy-based theory and friction coefficients at critical state as well as peak friction angles and dilation angles were estimated. As a result of tests it was found that uniaxial compressive strength and particle breakage of the parent rocks have crucial effect on internal friction angles; in addition, dilatancy at the failure showed strong relationship as well.

• Journal of the Korean Geotechnical Society
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• v.23 no.11
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• pp.59-66
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• 2007

In order to clarify the influence of gravel content on the mechanical properties of gravel-mixed decompose granite soils, large-scale one-dimensional compression tests were performed. The sample used in the study was a decomposed granite soil from Shimonoseki in Yamaguchi prefecture in Japan. After adjusting the grain size of the said soils, the specimen compacted with a certain level of compaction energy was put to the test. Based on the results obtained, when gravel-mixed decomposed granite soil was compacted at the same energy level, there existed the specific gravel content at which dry density was maximum and which also produced the minimum compression index. Furthermore, from these results, an expression based on a two-phase mixture theory was proposed to quantitatively evaluate the effects of gravel content and initial dry density and the material parameters calculated through the proposed method proved to exactly estimate the actual measuring value.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.429-432
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• 2009

The deformation and burst pressure of composite motor case highly depends on fiber material properties. Therefore, measuring exact fiber material properties is a priority item to develop a advanced composite motor case. However, the fiber material properties in composite motor case is very sensitive on the various processing variables (equipment, operator and environmental condition etc..)and size effect, so the fiber material properties can't be measured exactly from the existing specimen test method. This paper suggests a newly developed test method, hoop ring test, that is capable of pressure testing with ring specimens extracted from real composite motor case. The results of hoop ring test showed excellent agreement with measured fiber material properties from hydro-burst test with full scale composite motor cases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.65-74
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• 2015

In order to design an advanced composite materials drainage pipe structures for an undersea tunnel, mechanical properties for the lamina types of the structural member must be predetermined. It is also reported that the size effect of the specimen is significant. In this study the tensile tests for the lamina types of the structural member are conducted at the room temperature ($20^{\circ}C$) and the seawater temperature ($0^{\circ}C$). In addition, the mechanical properties are predicted by theory based on the rule of mixtures and elasticity solution technique. The predicted mechanical properties are compared with test results obtained by a test method. In the design of an advanced composite materials drainage pipe structural members for an undersea tunnel, the used mechanical properties must be applied at the room temperature with considering the modified factors. These are to be offered the datum for the design an advanced composite materials drainage pipe structures for an undersea tunnel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.54-58
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• 1996

In this paper, the structure, dieletric and piezoelectric properties of Pb(Fe$_{\frac{1}{2}}$/Sb$_{\frac{1}{2}}$$O_3$+ Pb(Zr$_{0.52}$ Ti$_{0.48}$ )O$_3$system ceramics were investigated and the effects of donor Nb$^{+5}$ on these properties were characterized for the application of the actuator. In xPb(Fe$_{\frac{1}{2}}$Sb$_{\frac{1}{2}}$)O$_3$+ (1-x) Pb(Zr$_{0.52}$ Ti$_{0.48}$ )O$_3$system ceramics, tetragonality decreased as x and Nb$_2$O$_{5}$ wt% were increased. In 0.05Pb(Fe$_{\frac{1}{2}}$Sb$_{\frac{1}{2}$}$)O$_3$+ 0.95 Pb(Zr$_{0.52}$ Ti$_{0.48}$ )O$_3$system, grain size was smallest but showed best dielectric and piezoelectric properties. The specimen sintered at 120$0^{\circ}C$ in 0.05pb(Fe$_{\frac{1}{2}}$Sb$_{\frac{1}{2}}$ )O$_3$+ 0.95 Pb(Zr$_{0.52}$ Ti$_{0.48}$ )O$_3$+ Nb$_2$O$_{5}$ 0.6wt% exihibited best piezoeletric properties such as $K^{p}$ =64%, d$_{33}$ =490 [$\times$10$^{-12}$ C/N] and strain was 1320[$\times$10$^{-6}$ Δ$\ell$/$\ell$]at AC 6kV/cm

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.40-48
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• 2013

Eco deck plate system is a construction method that deconstruction of galvanized steel sheets is possible by integrating steel-wire-integrated girders and the galvanized steel sheets with bolts. Therefore, compared with previous steel-wire-integrated deck plates which were joined by welding, the system is acknowledged as the construction method possible management and repair. This study conducted an experimental research by manufacturing total 24 full size specimens in a same condition for 12-shape specimens by two parts to evaluate structural behaviors of the eco deck plates. In the results after the test, permissible deflection for the construction load action was shown to be values under design values and satisfactory. The processing of lattice steel wires was presented to be structurally advantageous in being manufactured by cutting downward. Also, in case of a specimen that D13 as a steel wire was used, destruction occurred at the welding part of the bottom steel wire and the lattice steel wire, so improvement measures for the welding in factory manufacture are necessary.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.486-492
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• 2004

We report the crystallization and magnetic properties of non-equilibrium $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}(x=0.25, 0.50, 0.75)$ alloy powders produced by rod-milling as well as by new chemical leaching. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h or 500 h milling, only the broad peaks of nano bcc crystalline phases were detected in the XRD patterns. The crystallite size, the peak and the crystallization temperatures increased with increasing Fe. After being annealed at $600{^\circ}C$ for 1 h for as-milled alloy powders, the peaks of bcc $AlCu_{4}\;and\;Al_{13}Cu_{4}Fe_{3}\;for\;x=0.25,\;bcc\;AlCu_{4}\;and\;Al_{5}Fe_{2}\;for\;x=0.50,\;and\;Al_{5}Fe_{2},\;and\;Al_{0.5}Fe_{0.5}\;for\;x=0.75$ are observed. After being annealed at $500{^\circ}\;and\;600{^\circ}C$for 1 h for leached specimens, these non-equi-librium phases transformed into fcc Cu and $CuFe_{2}O_{4}$phases for the x=0.25 specimen, and into bcc ${\alpha}-Fe,\;fcc\;Cu,\;and\;CuFe_{2}O_{4}$ phases for both the x=0.50 and the x=0.75 specimens. The saturation magnetization decreased with increasing milling time for $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}$ alloy powders. On cooling the leached specimens from $800{\~}850^{\circ}C$,\;the magnetization first sharply increase at about $491.4{\circ}C,\;745{\circ}C,\;and\;750.0{\circ}C$ for x=0.25, x=0.50, and x=0.75 specimens, repectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.561-564
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• 2001

The cladding area of HANARO Research Reactor fuel rods should be checked not to have any defects larger than the size required at QA documents by using eddy torrent testing method doting fabrication process. To apply eddy current testing inspection to the fuel rods, encircling differential probes and standard specimen were designed and fabricated. The impedance of the fabricated probes was measured with impedance analyzer in order to cheek that the probe has a suitable impedance for the inspection frequency, and with this probe and MIZ-40A eddy current equipment, the detectability of this probes was investigated. The developed probes could detect artificial notch with 2mm length 10% depth of cladding thickness in cladding area. In addition, the probe was successfully applied to detect the defects in cladding area doting fabrication of the research reactor rods.