• 방사성폐기물학회지
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• 제6권2호
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• pp.111-117
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• 2008

배관 내부의 방사성 오염도를 측정하기 위한 ZnS(Ag)/플라스틱섬광체 조합의 알파/베타선 동시측정용 phoswich 검출기를 개발하였다. 알파/베타선 동시측정용 phoswich 검출기의 오염위치에 따른 검출 성능을 PSD (Pulse shape discrimination) 방법을 이용하여 평가하였다. 또한, 검출기를 방사성 오염물질로부터 보호하기 위한 오염방지용 필름에 대한 방사선 감쇄 정도를 실험적으로 평가하였다. PSD 방법으로 알파/베타선 분리 정도를 측정한 결과 충분히 알파와 베타선이 분리되었으며 오염방지용 필름의 적용 가능성을 확인하였다.

• 한국건설순환자원학회논문집
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• 제9권4호
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• pp.469-477
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• 2021

본 연구에서는 해양환경에 노출된 구조물의 내구성과 안전성 저하를 방지하는 셀룰로오스 방오 코팅제에 대한 기본적인 역학 성능을 평가하였다. 셀룰로오스 나노섬유와 AKD 및 폐유리 미분말을 주요 재료로 구성하여 제조하였으며, 접촉각 시험, 건조 시간, 점성 분석, 미세구조 분석을 실시하였다. 셀룰로오스 방오 코팅제를 1회 코팅할 경우 상대적으로 강재 시편에서 높은 소수성능을 발휘하는 것으로 나타났으며, 시멘트 모르타르에서는 AKD 함유량이 증가할수록 접촉각이 증가하는 것이 확인되었다. 3회 코팅시 최대 151.6°의 초소수성을 표면을 확인하였으며, 폐유리 미분말 혼입시 상대적으로 높은 소수성능을 갖는 것이 나타났다. 셀룰로오스와 증류수를 1:1 비율로 제조할 경우 의가소성 유체에 해당하여 코팅제로의 활용에 적합할 것으로 판단되었다.

• Geomechanics and Engineering
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• 제18권5호
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• pp.535-543
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• 2019

Building on/with expansive soils with no treatment brings complications. Compacted expansive soils specifically fall short in satisfying the minimum requirements for transport embankment infrastructures, requiring the adoption of hauled virgin mineral aggregates or a sustainable alternative. Use of hauled aggregates comes at a high carbon and economical cost. On average, every 9m high embankment built with quarried/hauled soils cost $12600MJ.m^{-2}$ Embodied Energy (EE). A prospect of using mixed cutting-arising expansive soils with industrial/domestic wastes can reduce the carbon cost and ease the pressure on landfills. The widespread use of recycled materials has been extensively limited due to concerns over their long-term performance, generally low shear strength and stiffness. In this contribution, hydromechanical properties of a waste tyre sand-sized rubber (a mixture of polybutadiene, polyisoprene, elastomers, and styrene-butadiene) and expansive silt is studied, allowing the short- and long-term behaviour of optimum compacted composites to be better established. The inclusion of tyre shred substantially decreased the swelling potential/pressure and modestly lowered the compression index. Silt-Tyre powder replacement lowered the bulk density, allowing construction of lighter reinforced earth structures. The shear strength and stiffness decreased on addition of tyre powder, yet the contribution of matric suction to the shear strength remained constant for tyre shred contents up to 20%. Reinforced soils adopted a ductile post-peak plastic behaviour with enhanced failure strain, offering the opportunity to build more flexible subgrades as recommended for expansive soils. Residual water content and tyre shred content are directly correlated; tyre-reinforced silt showed a greater capacity of water storage (than natural silts) and hence a sustainable solution to waterlogging and surficial flooding particularly in urban settings. Crushed fine tyre shred mixed with expansive silts/sands at 15 to 20 wt% appear to offer the maximum reduction in swelling-shrinking properties at minimum cracking, strength loss and enhanced compressibility expenses.

• Computers and Concrete
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• 제29권1호
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• pp.15-29
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• 2022

Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

• Journal of Microbiology and Biotechnology
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• 제33권1호
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• pp.1-14
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• 2023

Polyethylene terephthalate (PET) is a plastic material commonly applied to beverage packaging used in everyday life. Owing to PET's versatility and ease of use, its consumption has continuously increased, resulting in considerable waste generation. Several physical and chemical recycling processes have been developed to address this problem. Recently, biological upcycling is being actively studied and has come to be regarded as a powerful technology for overcoming the economic issues associated with conventional recycling methods. For upcycling, PET should be degraded into small molecules, such as terephthalic acid and ethylene glycol, which are utilized as substrates for bioconversion, through various degradation processes, including gasification, pyrolysis, and chemical/biological depolymerization. Furthermore, biological upcycling methods have been applied to biosynthesize value-added chemicals, such as adipic acid, muconic acid, catechol, vanillin, and glycolic acid. In this review, we introduce and discuss various degradation methods that yield substrates for bioconversion and biological upcycling processes to produce value-added biochemicals. These technologies encourage a circular economy, which reduces the amount of waste released into the environment.

• 한국인터넷방송통신학회논문지
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• 제20권2호
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• pp.239-246
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• 2020

본 논문에서는 우산의 물기를 건조하는 자동 제수 시스템을 제안한다. 우산의 물기 제거방법은 우산용 비닐을 씌우거나 사용자가 직접 우산을 털어 수동적으로 제거하는 번거로운 방법과, 수동으로 우산을 제수면에 접촉 시켜 물기를 제거하는 제수기를 사용하는 방법이다. 기본 방법은 수동으로 제거해야 하는 번거로움 뿐만 아니라 제수기의 물기 제거 성능도 만족할 만한 건조감을 기대하기 힘든 문제점이 있었다. 이러한 문제점을 해결하기 위하여 에어 컴프레셔를 이용하여 사용자가 우산을 넣으면 압력 센서가 넣어진 우산의 무게를 감지해, 모터를 구동시키는 방식으로 우산의 물기를 제거하는 시스템을 개발하였다. 본 발명품은 비닐을 사용하지 않아 폐비닐의 발생을 없앰으로써 경제적, 환경적인 효과를 얻을 수 있을 것으로 기대된다.

• 지질공학
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• 제8권3호
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• pp.225-234
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• 1998

지하공동의 거동은 굴착전에 암반에 존재하는 초기응력의 크기와 굴착에 따른 공동주변에서의 응력재분배에 많은 영향을 받는다. 암반과 같은 탄소성 재료인 경우 굴착으로 인한 공동주변의 거동은 응력경로의 영향을 받기 때문에 굴착방법과 순서 등에 따라 해석결과는 달라지게 된다. 따라서 지하 원자력발전소, 방사성폐기물 영구처분시설, 원유비축시설 등과 같은 대단면을 갖는 지하공동을 보다 합리적으로 설계하기 위해서는 해석과정에 굴착으로 인한 영향을 반영하는 것이 바람직하다. 본 연구에서는 굴착으로 인한 응력변화를 파악하기 위해서 유한요소법과 개별요소법에 의한 수치해석을 각각 수행하였다. 해석결과를 분석한후 합리적인 굴착단면형상, 굴착방법 및 순서, 지보효과, 다공동 굴착시 인접공동의 굴착으로 인한 영향 등을 검토하였다.

• 한국지반신소재학회논문집
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• 제12권3호
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• pp.55-64
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• 2013

본 연구는 포천석분을 재성형하여 등방압축-팽창시험과 구속압력을 달리한 일련의 비배수삼축압축시험을 실시하여 Lade 단일항복면 구성모델의 토질매개변수를 결정하였으며, 실험결과의 역해석을 통하여 단일항복면 구성모델의 적용성과 포천석분의 거동특성을 확인하였다. 그 결과 포천석분은 축변형률이 증가함에 따라 축차응력이 증가하는 경화현상을 보이고 있으며 큰축변형률에서 파괴되므로 실용적인 파괴기준을 검토할 필요성을 확인하였으며, 구성모델의 11개 토질매개변수를 이용하여 시험치를 역해석한 결과 응력-변형거동을 양호하게 예측하지만 항복함수에 관련된 토질매개변수를 파괴규준에 관련한 상관식과 상수로 역해석한 경우는 다소 상이한 양상을 보이고 있다.

• 한국환경과학회지
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• 제24권8호
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• pp.1037-1043
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• 2015

Since single-use disposable plastic usage has steadily been increasing, recent trends in polymeric research point to increasing demand for eco-friend materials which reduce plastic waste. A huge amount of non-degradable polypropylene (PP)-based pots for seedling culture are discarded for transplantation. The purpose of this study is to investigate an eco-friendly biodegradable material as a possible substitute for PP pot. The blend of poly(lactic acid) (PLA) with poly(butylene adipate-co-terephthalate) (PBAT) was used because of its good mechanical and flexible properties as well as biodegradation. After landfill, various properties of the blend pot were investigated by UTM, SEM, NMR and TGA. The results showed the tensile strength of the blend film rapidly decreased after 5 weeks of landfill due to degradation. From NMR data after landfill, the composition of PLA in the blend was decreased. These results indicate that the biodegradation of the blend preferentially occurs in PLA component. To investigate the effect of holes in pot bottom and side on root growth, a plant in the pot was grown. Some roots came out through holes as landfill period increases. These results indicate that the eco-friendly pot can be directly planted without the removal of pot.

• Environmental Engineering Research
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• 제23권3호
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• pp.250-257
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• 2018

We developed new composites by combining the solid waste from Low-Density Polyethylene in the form of plastic bag (PB) and biomass from rice husk (RH),in the form of $(RH)_x(PB)_{1-x}$ (x = (1, 0.9, 0.7, 0.5)), as alternative fuels for electrical energy sources, and for providing the best solution to reduce environmental pollution. Elemental compositions were obtained by using proximate analysis, ultimate analysis, and X-ray fluorescence spectroscopy, and the thermal characteristics were obtained from thermogravimetric analysis. The compositions of carbon and hydrogen from the ultimate analysis show significant increases of 20-30% with increasing PB in the composite. The activation energy for RH is 101.22 kJ/mol; for x = 0.9 and 0.7, this increases by 4 and 6 magnitude, respectively, and for x = 0.5, shows remarkable increase to 165.30 kJ/mol. The range of temperature of about $480-660^{\circ}C$ is required for combustion of the composites $(RH)_x(PB)_{1-x}$ (x = (1, 0.9, 0.7, 0.5)) to perform the complete combustion process and produce high energy. In addition, the calorific value was determined by using bomb calorimetry, and shows value for RH of 13.44 MJ/kg, which increases about 30-40% with increasing PB content, indicating that PB has a strong effect of increasing the energy realized to generate electricity.