• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.835-837
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• 2017

In this paper, manufacturing processes of cylindrical composite lattice structures using filament winding method was described. Cylindrical composite lattice structures were manufactured in accordance with four major steps. Silicon mold of lattice shape was installed on mandrel and then continuous fiber was wound on silicon mold. After winding process, in order to ensure the same thickness for all regions, compression process was done for its intersection parts. Finally, the composite lattice structure was demoulded after curing in oven. It was found that the manufactured cylindrical composites lattice structure had 2.4% of dimensional error compared to the design requirements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.77-86
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• 2024

In this study, authors attempted to determine the bond behavior characteristics to utilize Grid typed CFRP reinforcement as an alternative to steel rebar used as concrete reinforcement. Since it is difficult to understand the influence of the transverse grid length of the Grid typed CFRP reinforcement in the existing numerical analysis proposal for bond behavior, a nonlinear 3D model was created and finite element analysis was performed. To perform the analysis, the analysis was conducted by inputting a nonlinear material model and modeling the bond interface characteristics between the Grid typed CFRP reinforcement and concrete and comparing them with the actual direct pull-out test results. The bond behavior characteristics of the Grid typed CFRP reinforcement were found to be very dominated by the factors of the transverse grid, and showed a tendency to continuously increase load.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.5
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• pp.123-128
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• 2022

Applying rigorous modal transmission-line theory (MTLT), the properties of resonant diffraction gratings under conical light incidence is investigated. The mode vectors pertinent to resonant diffraction under conical mounting vary less with incident angle than those associated with diffraction gratings in classical mounting. Furthermore, as the evanescent diffracted waves drive the leaky modes responsible for the resonance effects, the conical mounting imbues diffraction gratings with larger angular tolerance than their classical counterparts. Based on these concepts, the angular-spectral and wavelength-spectral performance of resonant diffraction gratings in conical and classical mounts by numerical calculations with spectra found for conical incidence are quantified. These results will be useful in various applications demanding resonant diffraction gratings that are efficient and physically sparse.

• Composites Research
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• v.34 no.2
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• pp.129-135
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• 2021

In this paper, in order to examine the effect of fiber volume fraction non-uniformity in thickness direction on the buckling load of cylindrical composite lattice structures, we modified the equation of buckling load of the cylindrical composite lattice structures proposed by Vasiliev. The thickness of each layer of the rib was varied by fiber volume fraction, and material properties were applied differently by using the rule of mixture. Also, we performed linear buckling analysis by varying the structure size, thickness, and average value of the fiber volume fraction of finite element model. Finally, by comparing the calculation results of the buckling load of the equivalent model using the modified buckling load equation and the results of the finite element analysis, we found that the fiber volume fraction non-uniformity in thickness direction can reduce the buckling load of the cylindrical composite lattice structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.73-81
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• 2022

Recently, as the service life of structures increased, the load-carrying capacity of deteriorated reinforced concrete, where corrosion of reinforcing bars occurs due to various causes, is frequently decreased. In order to address this problem, many studies on the bond characteristic of FRP (Fiber Reinforced Polymer) bars with corrosion resistance, light weight and high tensile strength have been conducted, however there are not many studies on the bond characteristic of grid-typed CFRP embedded in concrete. Therefore, in order to evaluate the bond characteristics of grid-typed CFRP and its usability as a substitute for steel rebar, a pull-out test is performed using the longitudinal bond length and transverse grid length of the grid-typed CFRP as variables. Through the pull-out test, the bond load-slip curve of the grid-typed CFRP is derived, and the bond behavior is analyzed. The total bond load equation is proposed as the sum of the bond force of the longitudinal bond length and the shear force of the grid in the transverse direction. Also, expressing the area of the bond load-slip curve as total work, the change in dissipated energy with respect to the slip is analyzed to examine the effect of the tranverse grid on the bond force.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.56-64
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• 1996

In this study, a review is made of the previous work(Ref. 1 and 5) for the development of the limit design method of the flat rectangular grillages under the lateral pressure. And the effect of the in-plane loads on the collapse theory is considered. The main part of the work is devoted in developing the standard design method of grillages under the criteria of minimum weight and minimum cost. In the final part, it was shown that Pareto solution methods can be easily applied to structural optimization with the multiple objectives, and the designer can have an appropriate choice from those Pareto optimal solutions.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.63-67
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• 2015

In this study, we demonstrate the change of optical characteristic by thickness of metal deposition on nano metal grid polarizer film fabrication. Nano metal grid polarizer film consists of aluminium grid polarizer layer on PET (Polyethylene phthalate) substrate. We aim at metal grid layer formation for the large nano wire grid polarizer fabrication. we draw process conditions of the nano metal grid polarizer film fabrication to improve transmittance and extinction ratio and Nano wire grid polarizer film (NWGP) film is fabricated with 140 nm pitch, 70 nm width, and 70 nm depth of metal grid on optimum design conditions. As a result, we get high optical properties of nano wire grid polarizer which is the maximum transmittance of 80% and the extinction ratio of $10^6$ at 600 nm wavelength respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.8-12
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• 1989

In this paper, dielectric waveguide gratings, which can be applied to the nonreciprocal devices such as isolators, are proposed. Those grating structures can be considered as cascade connections of step discontinuities between uniform dielectric waveguides and another uniform dielectric waveguides with a ferrite layer. Therefore, the nonreciprocal scattering characteristics of such gratings can be obtained form the scattering characteristics of step discontinuities and uniform dielectric wave guides. For the periodic grating structures, band-reject characteristics can be located inside or outside the frequency range of interest. Numerical analyses are performed at 35GHz and experimental results at X-band are also presented.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.120-126
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• 2006

A grating-assisted fiber coupler(GAFC), which consists of a thin-film waveguide with grating and circular optical fiber, is proposed and the optimized power coupling is evaluated by using a technique amenable to rigorous longitudinal modal transmission-line theory(L-MTLT). In addition, novel criteria to couple an optical signal incident through the grating waveguide to a single-mode optical fiber are proposed. The numerical result reveals that the optimized power coupling occurs at minimum-gap condition between rigorous modes rather than for the conventional phase-matching condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.6
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• pp.74-86
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• 2021

The composite lattice structure is a structure that supports the required load with the minimum weight and thickness. Composite lattice structure is manufactured by the filament winding process using impregnating high-strength carbon fiber with an epoxy resin. Filament winding process can laminate and manufacture only structurally necessary parts, composite lattice structure can be applied to aircraft fuselages, satellite and launch vehicles, and guided weapons to maximize weight reduction. In this paper, the development and evaluation of the composite lattice structure corresponding to the entire process from design, analysis, fabrication, and evaluation of large-scale cylindrical and conical composites lattice structure were performed. To be applicable to actual projectiles and guided weapons, we developed a cylindrical lattice structure with a diameter of 2,600 mm and a length of 2,000 mm, and a conical lattice structure with an upper diameter of 1,300 mm, a lower diameter of 2,500 mm, and a length of 900 mm. The performance of the developed composite lattice structure was evaluated through a load test.