• Geomechanics and Engineering
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• 제25권2호
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• pp.143-157
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• 2021

Expansive soil is the most predominant geologic hazard which shows a large amount of shrinkage and swelling with changes in their moisture content. This study investigates the macro-mechanical and micro-structural behaviours of dredged natural expansive clay from coal mining treated with ordinary Portland cement or hydrated lime addition. The stabilised expansive soil aims for possible reuse as pavement materials. Mechanical testing determined geotechnical engineering properties, including free swelling potential, California bearing ratio, unconfined compressive strength, resilient modulus, and shear wave velocity. The microstructures of treated soils are observed by scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy to understand the behaviour of the expansive clay blended with cement and lime. Test results confirmed that cement and lime are effective agents for improving the swelling behaviour and other engineering properties of natural expansive clay. In general, chemical treatments reduce the swelling and increase the strength and modulus of expansive clay, subjected to chemical content and curing time. Scanning electron microscopy analysis can observe the increase in formation of particle clusters with curing period, and x-ray diffraction patterns display hydration and pozzolanic products from chemical particles. The correlations of mechanical properties and microstructures for chemical stabilised expansive clay are recommended.

• Computers and Concrete
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• 제24권2호
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• pp.125-135
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• 2019

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that SiO2 nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as SiO2 nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of SiO2 nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• 한국항행학회논문지
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• 제22권2호
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• pp.168-172
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• 2018

HACCP이란 식품의 원재료부터 제조, 가공, 보존, 유통, 조리단계를 거쳐 최종소비자가 섭취하기 전까지의 각 단계에서 발생할 우려가 있는 위해요소를 규명하고, 이를 중점적으로 관리하기 위한 중요관리점을 결정하여 자율적이며 체계적이고 효율적인 관리로 식품의 안전성을 확보하기 위한 과학적인 위생관리체계라고 할 수 있다. 본 논문에서는 HACCP의 체계적이고 효율적인 관리를 위해 식품의 유통 단계인 운송과정에서의 온도 및 습도를 측정하고, 이 정보를 통신망을 이용하여 주기적으로 서버에 전송하는 모니터링 단말기 및 이를 구현하는 firmware를 설계하였다. Sub-net에서 측정된 정보를 포함하여 단말기에서 전송된 데이터가 서버에 잘 저장되었으며 서버에서 보낸 응답도 단말기에 잘 수신됨을 확인하였다. 향후 이를 이용하여 식품의 이력관리 및 데이터 추적, 통계자료로 활용할 수 있을 것으로 기대된다. 또한 본 시스템은 학교나 직장 등 단체 급식소, 원재료나 식품 보관 등의 물류창고 등에서도 응용할 수 있는 시스템이 될 것으로 사료된다.

• 대한금속재료학회지
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• 제49권7호
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• pp.549-556
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• 2011

This study aimed to evaluate the performance of diffusion barriers in order to prevent fuel-cladding chemical interaction (FCCI) between the metallic fuels and the cladding materials, a potential hazard for nuclear fuel in sodium-cooled fast reactors. In order to prevent FCCI, Zr or V metal is deposited on the ferritic-martensitic stainless steel surface by physical vapor deposition with a thickness up to $5{\mu}m$. The diffusion couple tests using uranium alloy (U-10Zr) and a rare earth metal such as Ce-La alloy and Nd were performed at temperatures between 660~800$^{\circ}C$. Microstructural analysis using SEM was carried out over the coupled specimen. The results show that significant interdiffusion and an associated eutectic reaction ocurred in the specimen without a diffusion barrier. However, with the exception of the local dissolution of the Zr layer in the Ce-La alloy, the specimens deposited with Zr and V exhibited superior eutectic resistance to the uranium alloy and rare earth metal.

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.197-215
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• 2021

Under a severe environment of multiple hazards such as earthquakes and winds, the life-cycle performance of engineering structures may inevitably be deteriorated due to the fatigue effect caused by long-term exposure to wind loads, which would further increase the structural vulnerability to earthquakes. This paper presents a framework for evaluating the lifetime structural seismic performance under the effect of wind-induced fatigue considering different sources of uncertainties. The seismic behavior of a high-rise steel-concrete composite frame with buckling-restrained braces (FBRB) during its service life is systematically investigated using the proposed approach. Recorded field data for the wind hazard of Fuzhou, Fujian Province of China from Jan. 1, 1980 to Mar. 31, 2019 is collected, based on which the distribution of wind velocity is constructed by the Gumbel model after comparisons. The OpenSees platform is employed to establish the numerical model of the FBRB and conduct subsequent numerical computations. Allowed for the uncertainties caused by the wind generation and structural modeling, the final annual fatigue damage takes the average of 50 groups of simulations. The lifetime structural performance assessments, including static pushover analyses, nonlinear dynamic time history analyses and fragility analyses, are conducted on the time-dependent finite element (FE) models which are modified in lines with the material deterioration models. The results indicate that the structural performance tends to degrade over time under the effect of fatigue, while the influencing degree of fatigue varies with the duration time of fatigue process and seismic intensity. The impact of wind-induced fatigue on structural responses and fragilities are explicitly quantified and discussed in details.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1431-1438
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• 2022

In this study, natural radioactivity concentrations and dosimetric values of fly ash samples were evaluated for the landfill area of the coal-fired power plant (CFPP) complex at Binh Thuan, Vietnam. The average activity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were 93, 77, 92 and 938 Bq kg^-1, respectively. The average results for radon dose, indoor external, internal, and total effective dose equivalent (TEDE) were 5.27, 1.22, 0.16, and 6.65 mSv y^-1, respectively. The average emanation fraction for fly ash were 0.028. The excess lifetime cancer risks (ELCR) were recorded as 20.30×10^-3, 4.26×10^-3, 0.62×10^-3, and 25.61×10^-3 for radon, indoor, outdoor exposures, and total ELCR, respectively. The results indicated that the cover of shielding materials above the landfill area significantly decreased the gamma radiation from the ash and slag in the ascending order: Zeolite < PVC < Soil < Concrete. Total dose of all radionuclides in the landfill site reached its peak at 19.8 years. The obtained data are useful for evaluation of radiation safety when fly ash is used for building material as well as the radiation risk and the overload of the landfill area from operation of these plants for population and workers.

• 한국지반공학회논문집
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• 제24권5호
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• pp.15-25
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• 2008

본 논문에서 매년 항만개발 및 항로유지의 목적으로 발생하는 준설토사의 유효활용을 위하여 주요 항만 준설토사에 대하여 오염현황을 조사 및 분석하였다. 그리고 준설물질별 인간의 건강에 대한 피해확률을 과학적으로 추정하는 위해성 평가를 실시하여 공업 및 주거지역에서 직접 인체에 대하여 안전하고 유효하게 활용할 수 있는 기준을 제시하였다. 제시한 기준은 기존의 준설토사 처리.활용기준 및 토양환경보전법상의 환경기준보다 엄격한 것으로 나타났다. 그리고 유효활용에 대한 사전평가를 실시할 수 있는 관련 기준을 근거로 국내 주요항만의 발생준설토사에 대한 오염도를 평가한 결과, 일부 항만에서 카드뮴(Cd), 비소(As), 크롬(Cr) 및 아연(Zn)이 환경기준을 초과하는 것으로 나타나 정밀한 조사가 이루어져야 할 것으로 나타났지만 대부분 항만에서 발생한 준설토사는 유효활용이 가능한 것으로 나타났다.

• 한국산업융합학회 논문집
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• 제27권3호
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• pp.601-607
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• 2024

The discharge of oily wastewater into water bodies and soil poses a serious hazard to the environment and public health. Various conventional techniques have been employed to treat oil-water mixtures and emulsions; Unfortunately, these approaches are frequently expensive, time-consuming, and unsatisfactory outcomes. Porous materials and adsorbents are commonly used for purification, but their use is limited by low separation efficiencies and the risk of secondary contamination. Recent advancements in nanotechnology have driven the development of innovative materials and technologies for oil-contaminated wastewater treatment. Nanomaterials can offer enhanced oil-water separation properties due to their high surface area and tunable surface chemistry. The fabrication of nanofiber membranes with precise pore sizes and surface properties can further improve separation efficiency. Notably, novel technologies have emerged utilizing nanomaterials with special surface wetting properties, such as superhydrophobicity, to selectively separate oil from oil-water mixtures or emulsions. These special wetting surfaces are promising for high-efficiency oil separation in emulsions and allow the use of materials with relatively large pores, enhancing throughput and separation efficiency. In this study, we introduce a facile and scalable method for fabrication of superhydrophobic-superoleophilic felt fabrics for oil/water mixture and emulsion separation. AlN nanopowders are hydrolyzed to create the desired microstructures, which firmly adhere to the fabric surface without the need for a binder resin, enabling specialized wetting properties. This approach is applicable regardless of the material's size and shape, enabling efficient separation of oil and water from oil-water mixtures and emulsions. The oil-water separation materials proposed in this study exhibit low cost, high scalability, and efficiency, demonstrating their potential for broad industrial applications.

• 한국건축시공학회지
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• 제24권2호
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• pp.261-271
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• 2024

국내외 건설현장에서 사용빈도가 급격히 증가하고 있는 슬래브용 알루미늄 폼은 탈형시 바닥으로 그대로 떨어뜨리는 경우가 많아 소음으로 인한 주변 민원이 발생하고, 높은 위치에서 떨어지면서 형틀이 변형되거나 바닥에서 튀어 오로면서 주변 인부들에게 상해를 입히기도 하여 중대재해처벌법이 강화되는 현실에서 개선이 절실한 상황이다. 이에 본 연구에서는 공동주택의 1세대 슬래브 거푸집 전체가 동시에 작업자가 펼친 손이 닿는 위치까지 안전하게 낙하되면 자유롭게 분해하여 다음 층으로 인양할 수 있게 함으로써 안전성, 품질, 경제성, 공정이 개선된 필러서포터 존치형 공법으로써 슬래브의 처짐문제 해결 등의 장점을 확인되고 건설신기술을 획득하였으므로 적극적인 시장개척을 통한 적용 활성화가 가능할 것으로 판단된다.

• 한국가스학회지
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• 제28권1호
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• pp.35-43
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• 2024

산업 및 과학기술의 고도화로 인해 신규 화학물질 수와 사용량은 꾸준히 증가하고 있으며 이에 따른 화학물질 안전관리의 중요성이 사회적으로 부각됨에 따라 국민적 요구가 높아지고 있다. 정부적인 차원에서 화학물질의 안전관리에 대해 부처별로 역할을 구분하여 관리하고 있으나 시설 노후화 및 취급 부주의 등의 문제로 매년 화학물질로 인한 사고가 빈번하게 발생되고 있는 실정이다. 국내에서 발생한 화학물질 관련 사고사례를 바탕으로 사고 유형을 분석한 결과, 누출·폭발·화재·기타 등의 순으로 사고가 발생하고 있으며 사고의 원인은 시설결함, 안전관리 미준수로 순으로 분석되었다. 본 연구에서는 화학물질 중 불산을 취급하고 있는 사업장을 대상으로 HAZOP을 통해 취급공정에 대한 유해위험요인을 파악하여 Bow-Tie를 활용한 위험성평가를 수행하였다. 본 연구 결과를 바탕으로 동종·유사 사업장의 화학사고 예방을 위한 안전관리 계획을 개선할 수 있을 것이며 이를 통해 화학사고를 사전에 예방할 수 있는 화학안전관리 체계의 선진화에 기여할 수 있을 것으로 기대된다.