• 한국지반공학회논문집
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• 제20권7호
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• pp.99-105
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• 2004

포화점토가 보오링공에서 불교란시료로써 채취되면, 부의 간극수압이 체적팽창을 억제한다. 이 점토시료에는 지반중에서 작용한 평균주응력이 등방적으로 작용하며, 이 평균주응력은 수직응력보다 작고, 수평응력보다 크다. 그러므로 시료는 비배수조건하에서 수직으로 늘어나고, 수평으로 수축하게 된다. 통상적인 압밀시험은 이와 같이 변형된 시료를 그대로 사용하여 압밀링 크기와 똑같이 성형한 후 수행한다. 따라서 지반중의 유효상재압이 재하되면, 이 압력이 수평응력보다 크기 때문에 압밀량이 늘어나게 된다. 즉 압밀시험공시체는 현장의 압밀거동을 정확하게 나타내지 못하고 항상 아래에 위치하게 된다. 이 논문에서는 상기와 같은 시료변형의 영향을 고려하여, 압밀시험 공시체에 유효상재압이 재하되었을때 수평방향으로 비배수 변형하여 압밀링 내경에 밀착해도록 하였다. 그리고 제안하는 시험법의 적용성과 결과를 통상적인 압밀시험결과와 검토하였다.

• 공업화학
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• 제29권2호
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• pp.201-208
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• 2018

올소-타입 불포화폴리에스테르 수지와 이소-타입 불포화폴리에스테르 수지를 합성하여 폴리머 모르타르 복합재료의 폴리머 결합재로 사용하였다. 불포화폴리에스테르 수지의 희석제로는 스티렌 모노머와 아크릴로니트릴을 사용하였고, 경화제로 methyl ethyl ketone peroxide (MEKPO), 가속제로 cobalt octoate (CoOc)를 사용하였다. 수지의 형태와 희석제의 종류에 따라 4종의 불포화폴리에스테르 수지를 제조하여 공시체 제조의 폴리머 결합재로 사용하였다. 폴리머 결합재의 첨가량에 따라 총 16종의 폴리머 모르타르 공시체를 제작하여 내열수성 시험을 행한 후 압축 및 휨강도시험, 세공분석 및 SEM 분석을 실시하였다. 시험결과, 이소-타입 불포화폴리에스테르 수지를 폴리머 결합재로 사용한 공시체가 올소-타입 불포화폴리에스테르 수지를 사용한 공시체보다 더 우수한 강도를 나타내었다. 내열수성시험 후에 측정한 총세공량과 세공의 평균직경은 시험 전에 측정한 값에 비하여 감소되었다. 내열수성시험 전에 관찰한 사진에서 폴리머 결합재와 충전재 및 잔골재가 co-matrix 상으로 견고하게 결합되어 있었으나 내열수성시험 후에 관찰한 사진에서는 폴리머 결합재가 대부분 분해되어 있는 것을 관찰할 수 있었다.

• 한국재료학회지
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• 제22권2호
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• pp.66-70
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• 2012

Ti-Ni alloys are widely used in numerous biomedical applications (e.g., orthodontics, cardiovascular science, orthopaedics) due to their distinctive thermomechanical and mechanical properties, such as the shape memory effect, superelasticity and low elastic modulus. In order to increase the biocompatibility of Ti-Ni alloys, many surface modification techniques, such as the sol-gel technique, plasma immersion ion implantation (PIII), laser surface melting, plasma spraying, and chemical vapor deposition, have been employed. In this study, a Ti-49.5Ni (at%) alloy was electrochemically etched in 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF electrolytes to modify the surface morphology. The morphology, element distribution, crystal structure, roughness and energy of the surface were investigated by scanning electron microscopy (SEM), energy-dispersive Xray spectrometry (EDS), X-ray diffractometry (XRD), atomic force microscopy (AFM) and contact angle analysis. Micro-sized pores were formed on the Ti-49.5Ni (at%) alloy surface by electrochemical etching with 1M $H_2SO_4$+ X (1.5, 2.0, 2.5) wt% HF. The volume fractions of the pores were increased by increasing the concentration of the HF electrolytes. Depending on the HF concentration, different pore sizes, heights, surface roughness levels, and surface energy levels were obtained. To investigate the osteoblast adhesion of the electrochemically etched Ti-49.5Ni (at%) alloy, a MTT test was performed. The degree of osteoblast adhesion was increased at a high concentration of HF-treated surface structures.

• 공업화학
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• 제19권6호
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• pp.652-660
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• 2008

급냉 제강슬래그를 재활용하기 위하여 제강슬래그의 치환율을 다양하게 변화시켜 만든 EVA-폴리머 시멘트 모르타르의 기계적강도와 물성에 대하여 조사하였다. EVA-폴리머 시멘트 모르타르 공시체는 폴리머-시멘트비를 5단계(0, 5, 10, 15, 20 wt%), 급냉 제강슬래그의 치환율을 5단계(0, 25, 50, 75, 100 wt%)로 각각 변화시켜 총 25 종류의 공시체를 제작하였다. 공시체의 제 성능을 조사하기 위하여 후레쉬 모르타르의 물-시멘트비, 단위용적중량, 공기량과 경화 공시체의 압축 및 휨강도, 흡수시험, 내열수성시험, 세공분포측정 및 SEM에 의한 미세조직 관찰 등을 실시하였다. 그 결과 급냉 제강슬래그의 치환율이 증가됨에 따라 물-시멘트비는 감소되었으나 단위용적중량은 현저히 증가 되었다. 폴리머-혼화제 및 급냉 제강슬래그의 첨가량 증가에 따라 흡수율은 감소되었으나, 압축 및 휨강도는 현저히 증가되었다. 내열수성시험에 의하여 기계적강도는 현저히 감소되었으나, 세공량과 공극률은 현저히 증가되었다. 전자현미경 관찰에서 내열수시험 전의 조직은 견고하게 융착되어 있었으나 내열수시험 후의 조직에서는 폴리머-혼화제가 분해 또는 열화되어 있는 것을 관찰할 수 있었다.

• 한국지반환경공학회 논문집
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• 제11권6호
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• pp.77-83
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• 2010

본 연구에서는 화력발전소에서 발생한 바텀애쉬를 성토재로 사용하기 전 환경에 미치는 영향을 평가하고자 하였다. 바텀애쉬에 대한 기본 물성치는 공업분석, 원소분석, XRD, XRF를 통해 구하였고, 폐기물 용출실험, 토양오염 공정실험을 통해 바텀애쉬에 대한 폐기물 분류 및 토양오염 가능성을 평가하였다. 위 용출실험 결과는 국내 수질환경기준 및 지하수 수질기준과 비교하였고 수질오염의 가능성은 없는 것으로 평가되었다. 측정된 대부분의 중금속은 검출한도 이하였으며 $Cr^{6+}$의 경우 미량이 검출되었으나 기준치 이하였다. 컬럼실험에서는 Pb, Zn 및 황산염이 기준치를 초과하였으나, Pb과 Zn은 1 PVE 전에 모두 기준치 이하로 감소하였고 황산염은 기준치 이하로 감소하는데 최대 8 PVE의 시간이 소요되었다. 중금속의 경우 대부분이 기준치 이하이므로 문제가 없으나 황산염은 기준치를 10배 정도 초과하므로 사용에 주의를 요한다.

• 한국건설순환자원학회논문집
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• 제8권1호
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• pp.56-63
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• 2020

The usage of OPC-free alkali activated ground granulated blast furnace slag(GGBS) mortar has been widely studied on the previous years, due to its advantages on sustainability, durability and workability. This paper brings a new view, aiming to classify the best application in situ for each mortar, according to the type and activator content. By this practical implication, more efficiency is achieved on the construction site and consequently less waste of materials. In order to compare the different activators, the following experiments were performed: analysis of compressive strength at 28 days, setting time measured by needles penetration resistance, analysis of total pore volume performed by MIP and permeability assessment by RCPT test. In general, activated GGBS had acceptable performance in all cases compared to OPC, and remarkable improved durability. Following the experimental results, it was confirmed that each activator and different concentrations impose distinct outcome performance to the mortar which allows the classification. It was observed that the activator Ca(OH)2 is the most versatile among the others, even though it has limited compressive strength, being suitable for laying mortar, coating/plaster, adhesive and grouting mortar. Samples activated with NaOH, in turn, presented in general the most similar results compared to OPC.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.104-109
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• 2016

Purpose: The purpose of this study is to analyze fracture behavior and failure mechanism of porous titanium for dental implant fabricated by space holder process. Method: Three porous titanium specimens with a specific volume fraction of open pore were test by 3 point bending and compression stress condition, respectively. Fracture appearance was observed by scanning electron microscope and discussed in relation with oxygen content. Results: For compression-tested specimens, two specimen showed brittle failure, while the other one showed normal failure after deformation. High oxygen content was detected in the brittle-fractured specimen. Several micro-cracks initiated at the struts propagated down to the bottom of the specimen resulting in normal failure. Conclusion: Oxygen contamination during the fabrication process can leads brittle premature failure, and hence quality problem of the porous titanium for dental implant.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1996년도 경북지부 결성 및 추계학술발표회 논문집
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• pp.131-139
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• 1996

To quantitatively investigate the effects of manure compost on the soil and water environment including ground water the elution patterns of anions and hydraulic conductivity wore estimated with four different depth(15, 30, 45 60cm) and four variable ratio of compost treatment(0, 2, 4, 6%) through soil column test. 1. There were over 95% of elution of chloride and nitrate within 0.1 pore volume(PV), and sulfate within 0.2 PV. With 2 ton/10a of cow manure compost treatment recommended total 40 kg/10a of anions added was recovered as effluent at the amount of 17kg chloride, 5.4kg nitrate, and 13.2kg sulfate, respectively However, phosphate rarely recovered in the effluent due to the strong affinity for sorption sites in soils. 2. In multi-layered soil column the maximum peaks of each anion eluted were retardated with increasing soil depth and the amount of organic matter(OM) treatment. 3. With increasing OM up to 2% the saturated hydraulic conductivity(SHC) was greatly decreased, but the slight decrease in SHC was found by addition of OM greater than 4％. In multi-layered soil column SHC was more effected by the lower SHV layer than by that of the higher.

• 한국막학회:학술대회논문집
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• 한국막학회 1995년도 춘계 총회 및 학술발표회
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• pp.11-15
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• 1995

Polysulfone (PS) membranes were prepared by the phase inversion process using water or isopropanol as nonsolvent. The Flory-Huggins theory for a ternary system nonsolvent/solvent/polymer is applied to describe the thermodynamic equilibria of the components. The calculated ternary phase equilibria show that demixing of a PS binary solution with n-methylpyrrolidone (NMP) will be fast in a water coagulation bath and will be delayed in an isopropanol bath. The prepared membranes were characterized by SEM, gas adsorption-desorption measurement, and permeability test. The membrane, which is precipitated by fast demixing in a water bath, has nodular structures in the skin region and includes finger-like cavities in the sublayer. The membrane coagulated by isopropanol has a very dense and thick skin structure, which is formed by delayed demixing. The membrane coagulated by isopropanol showed considerably lower pore volume and surface area compared to that observed with water coagulation method. With dimethylformamide (DMF) as solvent and 2-3 wt% of water, the solution can show the liquid-liquid phase separation due to agglomation of the polymer-lean phase from the homogeneous solution. The membranes, which were coagulated near an equilibrium state, show the large (micron size) round pores in the whole membranes. The pores do not contribute the permeation characteristics.

• 한국식생활문화학회지
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• 제25권1호
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• pp.47-53
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• 2010

This study was conducted to investigate the effects of saltwort, on the quality characteristics of sponge cake. In addition, we examined the commercialization potential of sponge cake containing saltwort. To accomplish this, saltwort was added to sponge cakes at concentrations of 0%, 3%, 5% and 7% and quality and sensory tests were then conducted. The 7% group had the highest water and ash content. There was no difference in the fat content between samples. The control group showed the highest protein content and the lowest specific gravity. As the content of saltwort increased, the specific gravity of the sponge cake increased. Additionally, the dough yield and loss during baking were highest, in the control group, and these values decreased as the saltwort content increased. Similarly, the volume and specific volume were highest in the control group, and these values decreased as the content of saltwort powder increased. Color measurements of the samples, revealed that the L-value decreased as the content of saltwort powder increased. Furthermore, the a-value of the saltwort powder groups was higher than that of the control group and the b-value was highest in the 7% group. There were no differences in elasticity and cohesion between samples, but chewiness and brittleness increased the content of saltwort powder increased. The results of the sensory test revealed that the color, flavor and taste scores were the highest in the 5% group. The pore size was greatest in the control group, while hardness was greatest in the 7% group, chewiness was highest in the 5% group and moistness was highest in the 5% group. Finally, the overall preference was for the 5% group.