• ETRI Journal
• /
• v.25 no.2
• /
• pp.81-88
• /
• 2003

We designed a multimode interference (MMI) coupler to use in vertical coupling of double layered polymeric waveguides and analyzed the coupling characteristics by comparing our experimental and simulation results. We found that our proposed new structure, a stepped MMI coupler, is effective in vertical coupling between waveguide layers with a short length of MMI and has a high tolerance for the variation in the structure of an MMI coupler that can be induced as errors in the fabrication process.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.11a
• /
• pp.45-46
• /
• 2012

This study is intended to use the insulation effect of the dual bubble sheet to review the freezing prevention capability of underground walls by pouring the dual bubble sheet on the retaining walls before the concrete pouring to contemplate the temperature profile for each area of installation and the area of non-installation of the dual bubble sheet, and as a result, the temperature of the concrete was heightened than the ground due to the insulation effect in using the bubble sheet.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.1 s.190
• /
• pp.64-70
• /
• 2007

A long-exposing technique (LET) has been conducted to create nanoscale patterns applicable to diverse micro-devices using two-photon polymerization (TPP). By the weakly-polymerized region via the LET, double-layered embossing patterns can be fabricated simply in a single step. The LET makes possible a voxel and its surrounding to be fully grown into more than 500 nm in lateral size and weakly-polymerized region (WPR), respectively. In the WPR. interconnecting ribs between voxels are generated, and they lead to the creation of double-layered dot patterns. Moreover, by controlling the distance between voxels, various shapes of interconnecting rib can be fabricated when the LET is applied. Various embossing patterns were fabricated to evaluate the usefulness of the proposed technique as a novel nanopatterning technique in TPP.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.248-248
• /
• 2003

층상이중수화물(Layered Double Hydroxides, LDH)은 층 사이에 무기물 음이온이 있는 2차원 충상구조물로서 이들 층 사이의 공간에 이동 가능한 수화된 음이온의 존재로 전하균형을 이룬다. 층 사이의 음이온은 교환이 가능하며, 나머지의 공간은 물분자로 채워져 있다. 이러한 특성을 응용하여 LDH는 촉매, 음이온 교환제, 흡착제, 담체로 사용가능하며, 특히 음이온 교환능이 있는 소재로 고분자에 적용되고 있으며, 층간에 염료를 삽입한 복합체의 제조 둥에 관한 연구가 활발히 이루어지고 있다. 이의 적용에서 LDH의 입도는 결정적인 한계 요인으로 작용하기도 한다. 본 실험에서는 Mg-Al-NO$_3$ 층상이중수산화물(Mg-Al-NO$_3$-LDH)을 공침전법으로 합성하고, 양이온의 농도와 공침시 pH 및 교반조건의 변화가 생성된 LDH의 결정상, 형상, 입도, 및 양이온교환능에 미치는 영향을 알아보았다. 특히 초음파 분산법을 적용하는 경우 생성되는 LDH 입자크기의 미세화에 효과적인 것을 확인 할 수 있었다.

• Ceramist
• /
• v.22 no.3
• /
• pp.269-280
• /
• 2019

Ceramic layered double hydroxide (LDH) nanohybrids have attracted considerable interest in biomedical science due to their unique structural feature and characteristics in biological condition. Many studies on LDH nanoparticles have been reported in diagnosis applications including magnetic resonance imaging (MRI) contrast agents in order to not only provide better imaging performance through multimodal imaging strategy, but realize therapeutic function which treat cancers in one platform. This review highlights the recent progress in MRI T₁ contrast agent, dual modal imaging system, and MRI-guided drug delivery systems ranging from synthetic method and characterization to evaluation in vitro and in vivo based on the ceramic LDH nanohybrids. Future research directions are also suggested for next-generation bio-imaging contrast agent.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.4
• /
• pp.346-352
• /
• 1996

A wide-band design method of double layered electromagnetic wave absorbers cross-slotted in the second layer(which has very wide band frequency characteristics) is proposed and discussed. The wide-band electromagnetic wave absorber can be designed under some approximations by the the- oretical model using the equivalent material constants method applied to the second layer. Based on the developed model, wide-band electromagnetic wave absorbers with excellent reflectivity characteristics in the frequency range of 30MHz to 3, 170MHz were designed.

• Journal of Environmental Science International
• /
• v.23 no.7
• /
• pp.1333-1338
• /
• 2014

LDHs(layered double hydroxides) are of use adsorbent to remove heavy metals, micro-organic pollutants as well as high concentration of phosphorus from wastewater to low concentration of surface water without pH adjustments. This study examined the generation condition of LDHs saturated with phosphorus. Less than 20% regeneration rate was obtained in the absence of alkali and regeneration solution. After the desorption of LDHs with several conditions of acid and alkali solution, more than 60% of regeneration rate could be expected in the case of using $MgCl_2$ as regeneration solution.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.30A no.1
• /
• pp.44-50
• /
• 1993

In an attempt to improve the electrical characteristics of tantalum pentoxide dielectric film, silicon substrate was reacted with a nitrogen plasma to form a silicon nitride of 50.angs. and then tantalum pentoxide thin films were formed by reactive sputtering in the same chamber. Breakdown field and leakage current density were measured to be 2.9 MV/cm and 9${\times}10^{8}\;A/cm^{2}$ respectively in these films whose thickness was about 180.angs.. With annealing at rectangular waveguides with a slant grid are investigated here. In particular, 900.deg. C in oxygen ambient for 100 minutes, breakdown field and leakage current density were improved to be 4.8 MV/cm and 1.61.6${\times}10^{8}\;A/cm^{2}$ respectively. It turned out that the electrical characteristics could also be improved by oxygen plasma post-treatment and the conduction mechanism at high electric field proved to be Schottky emission in these double-layered films.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.7
• /
• pp.1720-1730
• /
• 1995

Finite-difference analysis was conducted to study the natural convection of a stably stratified salt-water solution in an annulus due to lateral heating. The main purpose of this study is to examine in detail the multi-layered flow structure. Calculation was thus made for R $a_{\eta}$=2*10$^{5}$ and 6.5*10$^{5}$ . Formation of layered flow structure, merging process of layers, the corresponding temperature and concentration distributions, Nusselt number variations with time are examined. Numerical results show that in each layer, the temperature profile looks 'S`-shaped and the concentration profile is uniform due to the convective mixing. The formation of the roll and the layer is governed by natural convection due to the temperature gradient and the merging process of the layer by diffusion of the concentration.ation.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.05a
• /
• pp.81-83
• /
• 2012

This paper is to compare the temperature history of the concrete using existing curing sheet and developed curing sheet made with double layered bubble sheet subjected to clod climate. Field application was conducted. According to results, application of developed curing sheet makes the temperature of curing house and concrete higher than existing curing sheet by about 3℃. This is due to the lower thermal conductivity of developed curing sheet.