• Journal of the Korean GEO-environmental Society
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• v.15 no.11
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• pp.61-66
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• 2014

The various recycling methods of mixed coal ash have been developed considerably and it's recycling quantity has been increased. However, the more relatively finer grain content of coal ash in ash pond is increased the more it's quantity is increased in recycling as products for drainage in soft ground etc. Accordingly, the geotechnical properties of mixed coal ash in ash pond would be inferior and it's recycling rate should reach the limitations in increase. In this study, to recycle mixed coal ash contained fine grain in considerably amount as products for strength, etc. By adding binder to it and manifesting, it's compressive strength is stronger than the criteria, these are suggested; 1) the variety of compressive strength test performed on mixed coal ash of various grain distributions as main material, 2) the kind of binder, it's mixing quantity and the optimum content rate range of fine grain coal ash that the compressive strength stronger than a certain compressive strength is manifested. Cement is more excellent than quicklime as binder in manifesting stronger compressive strength and the sieve type to sort it is #40 sieve in order to recycle all mixed coal ash in ash pond efficiently as products for drainage as well as products for strength, etc. And, it could increase insufficient compressive strength remarkably that content of pure sand is more in the rate as pure sand and the part of mixed coal ash in ash pond to pass through #40 sieve is mixed in the ratio of 2 to 8.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Resources Recycling
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• v.17 no.1
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• pp.29-37
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• 2008

Recently, domestically and internationally, the occurrences of Waste Glass are on the increase. Most of scrap glass are either reused of recycled. However, glass not recycled is buriedand is causing secondary environmental problem. With 5% mixture of Waste Glass, the average paste viscosity (rheology) decreased by 22.3% and 28-day compressive strength of mortar's flow and aging decreased by 1.5% and 6% respectively. Also, as Waste Glass mixture ratio of un-hardened elf-compacting concrete increased, fluidity increased and compressive strength decreased. In consideration of adequate compressive strength and fluidity that meets the 2nd class JSCE regulations; optimum mixture ratio of Waste Glass can be concluded as 20%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.465-468
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• 2008

This study investigated the best condition when mixed sand with a river and crushed sand was used though the experiment for the properties of the concrete corresponding to the control of fine aggregate ratio to apply the mixed sand and properties of the fine aggregate at the ready-mixed concrete factory on Yeongnam and Honam. The physical properties of Yeongnam and Honam is satisfied with KS F 2526 and KS F 2527 except fineness modulus and passing amount of 8mm sieve. And, the mixed sand above two types which were incongruent to use individually was being used at each factory, and it was managed in accordance with KS. The flowabillity of the mixture proportion of concrete which was estimated by method of unit volume weight according to the fine aggregate ratio at each factory on Yeongnam and Honam was higher than existing mixture proportion. It was analyzed that the residual water due to decline of the surface area caused by reducing fine aggregate ratio was increased relatively. Accordingly, it was considered that the effect on the economic mixture proportion and improvement of durability might be possible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.267-268
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• 2007

기존의 Free Sintering 방법을 사용하는 LTCC(Low Temperature Cofiring Ceramics)는 수축률이 일정하지 않아서 설계 치수와 동일하게 제작하기 어려운 단점을 가지고 있다. 이에 따라서 정밀한 전자부품을 제작하기 위한 방안으로 X-Y면 방향에서의 변형을 거의 zero로 제어하는 Constrained Sintering(CS) 기술이 요구되고 있다. 본 연구에서는 LTCC 기판이 소성되는 동안에 변형을 억제하기 위하여 소성온도가 LTCC 기판 보다 높은 $Al_2O_3$ 분말과 유기물을 혼합하여 페이스트를 제작한 후에 스크린 프린팅 방법을 이용하여 도포 후에 Z축 방향으로 일축가압을 하면서 소성하여 수축률을 제어 하였다. 또한 바인더와 $Al_2O_3$ 분말의 함량에 대한 최적 조성의 $Al_2O_3$ 페이스트를 제작하여 0.5%로 수축률을 가지는 균일한 LTCC 기판을 구현 할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.47.2-47.2
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• 2010

For reducing outer reflection in mono-crystalline silicon solar cell, wet texturing process has been adapted for long period of time. Nowadays mixed solution with potassium hydroxide and isopropyl alcohol is used in silicon surface texturing by most manufacturers. In the process of silicon texturing, etch rate is very critical for effective texturing. Several parameters influence the result of texturing. Most of all, temperature, process time and concentration of potassium hydroxide can be classified as important factors. In this paper, temperature, process time and concentration of potassium hydroxide were set as major parameters and 3-level test matrix was created by using robust design for the optimized condition. The process optimization in terms of lowest reflection and stable etch rate can be traced by using robust design method.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.90-90
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• 2000

이온빔을 이용한 리소그래피의 경우 미크론 이하의 미세구조를 형성할 수 있는 유용한 수단으로서 방사광 X-선과 함께 주목을 받고 있으며, 이와 같은 미세구조 제작은 MEMS (Micro Electro-Mechanical System) 개발에 있어서 매우 중요하다. 그러나 이온빔을 이용한 리소그래피에 대한 연구가 많이 이루어져 있지 않은 상태이다. MeV급 양정사 빔을 이용한 리소그래피의 가능성을 확인하기 위하여 기본적인 실험을 수행하였으며, 최적 이온빔 조사 조건 및 최적 현상 조건을 도출하였다. Resist로는 PMMA를 사용하였으며, 1.8 MeV 양성자 빔을 사용하여 50$\mu\textrm{m}$ 깊이의 구조물을 만들었다. 1.8MeV 양성자 빔의 조사선량이 7x1013ions/cm2 이상이 되면 PMMA 내부에 기포가 형성되므로 적정 조사선량을 4x1013 ions/cm2으로 결정하였다. 또한 선량을 4x1013ions/cm2 으로 고정하고 선량률을 변화시켜주면 선량률이 8x1011ions/cm2S 일 때부터 시료에 기포나 터짐 현상 등의 문제가 발생하였으며 5x1010~~1x1010ions/cm2s 의 선량률이 조사시간, 결함측면에서 가장 적합한 영역임을 알 수 있었다. 현상제로는 20% morpholine, 5% etanolamine 60% diethylenglykol-monobutylether, 15% 증류수를 혼합하여 사용하였다. 현상 온도를 30~5$0^{\circ}C$로 변화시켜서 현상을 한 결과, 4$0^{\circ}C$에서 현상 소요시간은 1시간 이내이며 SEM으로 관찰된 표면의 상태도 제일 양호한 결과를 보였다. 82 mesh 밀도, 선굵기 60$\mu\textrm{m}$, 크기 20x20 mm인 백금 망을 마스크로 사용하여 실제 3차원 미세구조를 제작하여 보았다. 그림 1에서 제작된 구조물의 SEM 사진을 보여주었으며, 식각된 면의 조도가 매우 뛰어나며 모서리의 직각성도 우수함을 확인할 수 있다. 이와 같이 도출된 시험 조건을 기초로 하여 리소그래피 후에 전기 도금을 이용한 금속 몰드 제작 및 이온빔 리소그래피 장점을 최대한 살릴수 있는 미세구조 제작에 대한 연구를 계속 추진할 계획이다.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.5
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• pp.392-399
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• 2007

This study was carried out to assess optimum conditions of peatmoss-based substrates for red pepper plug seedlings. Peatmoss-based substrates prepared by mixing of peatmoss with vermiculite, perlite, rice hull and zeolite at various mixing ratios were used for growing pepper plug seedlings. The physical and chemical properties of the peatmoss substrate were analyzed by the CEN(European committee for standardization) method. Fresh and dry weights (shoot, root), leaf area, root length and T/R ratio (dry shoot weight/dry root weight) were determined at 55 days after sowing. The results showed that the growing media PVSZ 6 (peatmoss:silver vermiculite: zeolite=6:3.9:0.1) and PVGZ 6 (peatmoss:gold vermiculite: zeolite=6:3.9:0.1) can successfully be used for red pepper plug seedlings judging from dry weight and T/R ratio of the plug seedlings. The optimal ranges of total pore space, water volume, air volume, easily available water content and water buffering capacity of the peatmoss based growing media for pepper plug seedlings were 87~93%, 52~71%, 20~41%, 10~37% and 0.6~10%, respectively.

• Resources Recycling
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• v.29 no.3
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• pp.51-60
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• 2020

This study was carried out to get the optimum conditions for manufacturing high refractive glass beads from waste fluorescent lamp glass. Chemical composition, X-ray diffraction pattern, particle size distribution, refractive index of glass beads, and the effect of air mixing ratio and ejection rate were investigated. The obtained results are as follows. The X-ray diffraction pattern and chemical composition of glass beads made of waste fluorescent glass are similar to common glass except ReO₂ 0.0108 wt%, BaO 0.071 wt%, NiO 0.0039 wt% and CaO 7.8 wt% but 11.7 wt% of common glass. The glass beads made of waste fluorescent lamp glass have the narrower particle size distribution of and the higher refractive index than the glass beads made of common glass. The optimal conditions of kiln operation for manufacturing glass beads from waste fluorescent lamp glass are 20 m/sec of ejection rate, 1.7 of air mixing ratio, and 940℃ of temperature.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.3
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• pp.289-296
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• 2007

Porous media for sewage treatment were developed through a pyrolysis process of food wastes with loess in the study. This work was carried out in two consecutive stages; in the first stage, new porous media were prepared through a high temperature pyrolysis process, and then the resultant media were applied to a simple lab-scale sewage treatment process in the second stage. To determine the optimum operating conditions of pyrolysis and mixing ratio of materials, physical properties such as specific surface area, porosity and compressive strength of final products were analyzed. The removal efficiencies of TOC and COD were measured to evaluate the effectiveness of resultant porous media. As a result of the experiment, we found that the best mixing ratio of food wastes to loess was 1 : 1 at $1,100^{\circ}C$. Average porosity of the developed media was 37.0%, in which pore size ranged from 1 to $20{\mu}m$, showing quite vigorous microbial activation. After immersing the media into a reactor for sewage treatment for eight days, removal efficiencies of TOC and COD were 87.3% and 85.0%, respectively.