• Computers and Concrete
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• 제23권2호
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• pp.107-119
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• 2019

In-service reinforced concrete structures are simultaneously subjected to a combination of multi-deterioration environmental actions and mechanical loads. The combination of two or more deteriorative actions in environments can potentially accelerate the degradation and aging of concrete materials and structures. This paper reviews the coupling and synergistic mechanisms among various deteriorative driving forces (e.g. chloride salts- and carbonation-induced reinforcement corrosion, cyclic freeze-thaw action, alkali-silica reaction, and sulfate attack). In addition, the effects of mechanical loads on detrimental environmental factors are discussed, focusing on the transport properties and damage evolution in concrete. Recommendations for advancing current testing methods and predictive modeling on assessing the long-term durability of concrete with consideration of the coupling effects are provided.

• Current Photovoltaic Research
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• 제9권2호
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• pp.36-44
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• 2021

To endorse the reliability and durability of the solar photovoltaic (PV) device several tests were conducted before exposing to the outdoor field in a non-ideal condition. The PV module has high probability that intend to perform adequately for 30 years under operating conditions. To evaluate the long term performance of the PV module in diversified terrestrial conditions, one should use the outdoor performance data. However, no one wants to wait for 25 years to determine the module reliability. The accelerating stress tests performing in the laboratory by mimicking different field conditions are thus important to understand the performance of a PV module. In this review, we will discuss briefly about different accelerating stress types, levels and prioritization that are used to evaluate the PV module reliability and durability before using them in real field.

• 소성∙가공
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• 제33권4호
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• pp.261-269
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• 2024

This study aimed to optimize the MIL-53 metal-organic framework coatings for enhanced durability in carbon dioxide capture applications. We synthesized MIL-53 powders using a hydrothermal method and deposited them on stainless-steel substrates by spin coating at various speeds, ranging from 300 to 2,000 rpm. The microstructure, surface properties, and tribological characteristics of the coatings were analyzed systematically. The results indicated that the spin speed significantly impacted the coating uniformity and defect formation. Coatings prepared at moderate speeds of 500 to 1,000 rpm exhibited optimal thickness and density, resulting in superior wear resistance. The tribological tests revealed that the coatings prepared at 700 to 1000 rpm had the lowest wear rates. These findings offer valuable insights for the development of durable MOF-based coatings for carbon dioxide capture and other applications requiring long-term stability under mechanical stress.

• 한국정밀공학회지
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• 제26권6호
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• pp.114-121
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• 2009

Mobile phone is a representative personal communication tool among wireless communication devices. Recently, with the miniaturization and light-weight trend of mobile phone, the vibration motor has been replaced by coin type. The required performances of coin type vibration motor needed by user are long life, higher vibration, and thin thickness. Also the most important factor determines the performance of vibration motor is long-term reliability, which is mainly related to PCB plating technique for commutator. In this study, three types of fault were categorized to analyze the cause for malfunction of vibration motor. And, hardness and surface morphology on plating surface are also investigated to optimize the plating method and plating conditions. As a result, new plating method and conditions were proposed to increase the durability of PCB commutator.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.809-812
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• 2008

지난 수년간 콘크리트의 염소이온 침투와 유관되어 실험방법론 및 해석적 모델 기법의 개발에 많은 발전이 있어왔다. 그러나 실제 콘크리트 구조물에는 다소의 균열이 존재하며 이는 장기 내구성에 큰 영향을 줄 수 있음에도 불구하고, 대부분의 연구들은 비균열의 콘크리트를 대상으로 연구되어 온 문제점이 있었으며 균열이 존재하는 콘크리트의 염소이온 침투에 대한 연구는 매우 드문 실정이다. 본 연구의 저자는 단기 촉진실험에 의하여 균열이 염소이온에 미치는 영향을 살펴보았다. 그러나 신뢰성있는 결과를 얻기 위해서는 장기 실험을 통한 고찰이 필요하다. 본 연구의 목적은 장기 및 단기 실험결과를 비교하였는데, 자기치료 효과에 의하여 균열이 시간이 경과함에 따라 감소하는 뚜렷한 경향을 확인할 수 있었다.이러한 경향은 균열 폭이 클수록 자기치료에 의한 균열감소 효과가 더욱 뚜렷하였다.

• 콘크리트학회논문집
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• 제20권6호
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• pp.773-784
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• 2008

동의 제련과정에서 생성되는 동슬래그의 건설용 골재 활용이 국내에서도 2004년부터 가능하게 되었으나, 현재까지 장기적인 안정성 즉, 내구성에 대한 충분한 판단자료가 미흡하여 실용화를 저해하는 한 요인으로 작용하고 있다. 본 연구에서는 동슬래그를 천연모래 (잔골재)의 부분 치환재로 사용한 콘크리트의 내구적 특성을 18 MPa 및 27 MPa급 상용 콘크리트에 대해 촉진 및 폭로 실험을 수행하여 규명하고, 이를 통해 동슬래그 콘크리트의 실용화를 가속시키기 위한 토대를 마련하고자 하였다. 실험결과, 동슬래그 30% 치환조건에서는 대부분의 천연모래를 사용한 배합과의 내구특성 차이가 크지 않은 것으로 나타났으며, 부순모래를 사용한 경우는 대체로 50% 치환조건과 유사한 것으로 확인되었다. 특히 8년간 진행된 폭로실험 결과에서도 천연모래만을 사용한 경우와 대비하여 동등한 정도의 내구성을 확보함은 물론, 저품위인 18 MPa 콘크리트의 경우에도 피복두께 20 mm까지 중성화에 도달하는 수명을 50년 이상 확보할 수 있음을 알 수 있었다.

• Computers and Concrete
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• 제25권2호
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• pp.119-132
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• 2020

There is a growing interest in the use of by-product materials such as ceramics as alternative materials in construction. The aim of this study is to investigate the mechanical properties and durability of sustainable concrete containing waste ceramic powder (WCP), and to predict the results using artificial neural network (ANN). In this order, different water to binder (W/B) ratios of 0.3, 0.4, and 0.5 were considered, and in each W/B ratio, a percentage of cement (between 5-50%) was replaced with WCP. Compressive and tensile strengths, water absorption, electrical resistivity and rapid chloride permeability (RCP) of the concrete specimens having WCP were evaluated by related experimental tests. The results showed that by replacing 20% of the cement by WCP, the concrete achieves compressive and tensile strengths, more than 95% of those of the control concrete, in the long term. This percentage increases with decreasing W/B ratio. In general, by increasing the percentage of WCP replacement, all durability parameters are significantly improved. In order to validate and suggest a suitable tool for predicting the characteristics of the concrete, ANN model along with various multivariate regression methods were applied. The comparison of the proposed ANN with the regression methods indicates good accuracy of the developed ANN in predicting the mechanical properties and durability of this type of concrete. According to the results, the accuracy of ANN model for estimating the durability parameters did not significantly follow the number of hidden nodes.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2002년도 학술대회지
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• pp.355-358
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• 2002

국내에서 1960년대부터 공동주택의 활발한 보급이 이루어지고 있는 반면, 공동주택의 물리${\cdot}$사회적 성능을 유지하여 수명을 연장시키기 위한 제도 및 표준적 유지관리 기법 등이 마련되지 못하여 시설안전 및 주거환경 문제가 발생하게 되었다. 이러한 현 상황 하에 공동주택의 유지관리를 통하여 주택의 수명을 증진함으로써 주택자원의 효율적인 이용이 시급한 실정이다. 공동주택의 유지관리 업무 측면에 있어 정확한 장기수선계획의 수립과 그에 따른 특별수선충당금 산정은 주택의 조기 노후화를 방지할 수 있다. 하지만 유지관리 행위주체인 주택 관리자들뿐 아니라 유지관리 대상시설물에 거주하는 입주자들에게 있어서 정확한 장기수선계획의 수립과 그에 따른 특별수선충당금의 적립에 관한 필요성 의식이 불충분한 현실이다. 장기수선계획의 미수립은 특별수선충당금의 비합리적인 적립을 허용하는 결과를 초래하고 있다. 따라서, 공동주택의 성능을 최대한 발휘하도록 하여 건물의 경제적 수명을 연장시키기 위하여 정확한 근거에 의한 장기수선계획의 수립과 그에 따른 특별수선충당금산정 방법을 제시하고자 한다.

• Advances in concrete construction
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• 제5권3호
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• pp.271-288
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• 2017

This paper aims to investigate the effects of replacing cement with ground granulated blast furnace slag (GGBFS) in self compacting concrete in the fresh and hardened state. The performance of SCC in moderate climate is well investigated but few studies are available on the effect of hot environment. In this paper, the effect of initial water-curing period and curing conditions on the performance of SCC is reported. Cement was substituted by GGBFS by weight at two different levels of substitution (15% and 25%). Concrete specimens were stored either in a standard environment (T=$20^{\circ}C$, RH=100%) or in the open air in North Africa during the summer period (T=35 to $40^{\circ}C$; R.H=50 to 60%) after an initial humid curing period of 0, 3, 7 or 28 days. Compressive strength at 28 and 90 days, capillary absorption, sorptivity, water permeability, porosity and chloride ion penetration were investigated. The results show that the viscosity and yield stress are decreased with increasing dosage of GGBFS. The importance of humid curing in hot climates in particular when GGBFS is used is also proved. The substitution of cement by GGBFS improves SCC durability at long term. The best performances were observed in concrete specimens with 25% GGBFS and for 28 days water curing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1108-1109
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• 2008

To survive in outdoor environments, photovoltaic modules rely on packaging materials to provide requisite durability. We analyzed the properties of encapsulant materials that are important for photovoltaic module packaging. Recently, the thickness of solar cell gets thinner to reduce the quantity of silicon. And the reduced thickness make it easy to be broken while PV module fabrication process. Solar cell's micro cracks are increasing the breakage risk over the whole value chain from the wafer to the finished module, because the wafer or cell is exposed to tensile stress during handling and processing. This phenomenon might make PV module's maximum power and durability down. So, when using thin solar cell for PV module fabrication, it is needed to optimize the material and fabrication condition which is quite different from normal thick solar cell process. Normally, gel-content of EVA sheet should be higher than 80% so PV module has long term durability. But high gel-content characteristic might cause micro-crack on solar cell. In this experiment, we fabricated several specimen by varying curing temperature and time condition. And from the gel-content measurement, we figure the best fabrication condition. Also we examine the crack generation phenomenon during experiment.