• Design & Manufacturing
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• v.16 no.3
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• pp.9-15
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• 2022

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1117-1118
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.315-316
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.239-240
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• 2007

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.255-258
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• 2000

The new approach for synthesis of novel condensation monomers and polyimides on the basis of them was developed. The correlation between synthesis regularities, structure and properties of monomers and polyimides was studied. The areas of industrial application of synthesized polymer were determined.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.22-28
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• 2016

In this study, we fabricated high quality color conversion component with green/red phosphor and low melting glass frit. The color conversion component was prepared by placing the green and red phosphor layer on slide glass via screen printing process. The properties of color conversion component could be controlled by changing coating sequence, layer thickness and heat treatment temperature. We discovered that optical properties of color conversion component were generally determined by the lowest layer. On the other hand, the heat treatment temperature also affected to correlated color temperature (CCT) and color rending index (CRI). The color conversion component with a green (lower) - red (upper) layer which was sintered at $550^{\circ}C$ showed the best optical properties: CCT, CRI and luminance efficacy were 3340 K, 78, and 56.5 lm/w, respectively.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.96-101
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• 2017

In this article, pure $m-LaVO_4:Eu^{3+}$ and $t-LaVO_4:Eu^{3+}$ nanocrystals were prepared by an EG-assisted hydrothermal method with regular shapes. A series of controlled experiments showed that the pH value of a mixed solution, the volume ratio of $EG/H_2O$ and the dosage of the doped $Eu^{3+}$ all had an important effect on the sizes and shapes of the final products. Furthermore, the constitutional unit of the products changed from 0D to 2D with an increase in the EG dosage. The PL results showed that $t-LaVO_4$ doped with $Eu^{3+}$ ions had better luminescence properties than $m-LaVO_4$ due to its special structure. All of these results not only expand our understanding of the luminescence properties of lanthanide orthovanadates, but they also elucidate the principles of the crystal growth.

• Advances in aircraft and spacecraft science
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• v.4 no.5
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• pp.585-611
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• 2017

This article covenants with the post buckling witticism of carbon nanotube reinforced composite (CNTRC) beam supported with an elastic foundation in thermal atmospheres with arbitrary assumed random system properties. The arbitrary assumed random system properties are be modeled as uncorrelated Gaussian random input variables. Unvaryingly distributed (UD) and functionally graded (FG) distributions of the carbon nanotube are deliberated. The material belongings of CNTRC beam are presumed to be graded in the beam depth way and appraised through a micromechanical exemplary. The basic equations of a CNTRC beam are imitative constructed on a higher order shear deformation beam (HSDT) theory with von-Karman type nonlinearity. The beam is supported by two parameters Pasternak elastic foundation with Winkler cubic nonlinearity. The thermal dominance is involved in the material properties of CNTRC beam is foreseen to be temperature dependent (TD). The first and second order perturbation method (SOPT) and Monte Carlo sampling (MCS) by way of CO nonlinear finite element method (FEM) through direct iterative way are offered to observe the mean, coefficient of variation (COV) and probability distribution function (PDF) of critical post buckling load. Archetypal outcomes are presented for the volume fraction of CNTRC, slenderness ratios, boundary conditions, underpinning parameters, amplitude ratios, temperature reliant and sovereign random material properties with arbitrary system properties. The present defined tactic is corroborated with the results available in the literature and by employing MCS.

• 보존과학연구
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• s.21
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• pp.101-118
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• 2000

Stone cultural properties(pagoda, Buddhist statue etc.) is moved in original place for many reasons and restored after taking to pieces for structural safety. With the movement and restoration after taking to pieces, the cast iron is used for the sake of a fixation and horizontality. The stone cultural properties are spoiled the beauty and accelerated the weathering because of the corrosion product of cast iron. So we need to substitute for the improved property in all aspects. We are executed the corrosion test and inquired the property of material on the usable material for the shim of stone cultural properties. That is the Cast iron, Stainless steel, Titanium and Fiber Reinforced Plastics. In the result of the physical property and strength, the Stainless steel and Titanium was superior to the Cast iron. And the Stainless steel and Titanium was slower than the Cast iron in the corrosion velocity for the acid, salt and rain. If the shim is substitute the Stainless steel or Titanium for the Cast iron, the stone cultural properties are able to reduce the pollution of stone cultural properties by corrosion product and should not happen in the matter of stone pagoda.

• Journal of Ocean Engineering and Technology
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• v.14 no.3
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• pp.90-99
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• 2000

This study has been investigated about the influence of moisture environment properties in the unidirectional and cross laminated carbon fiber/epoxy and glass fiber/epoxy composites. As a results, it was found that the weight gain of water increased with the immersion time and the mechanical properties were decreased with the weight gain of water. And it was also shown that the mechanical properties of carbon fiber/epoxy laminates were better than those of glass fiber/epoxy laminates. And a gap of the mechanical properties between the two kinds of laminates was increasing with the immersion time in distilled water of 80$^{\circ}C $. Mechanical properties which decreased by moisture absorption in the CF and GF reinforced laminates were recovered up to some extent by drying in oven at 80$^{\circ}C $ for 10 days.