• Title/Summary/Keyword: Failure Mitigation

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Study of Light-induced Effect on Silicon Solar Cell from Wafer to Cell: A Review (광조사에 의한 실리콘 태양전지 열화 연구)

  • MyeongSeob Sim;Dongjin Choi;Myeongji Woo;Ji Woo Sohn;Youngho Choe;Donghwan Kim
    • Current Photovoltaic Research
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    • v.12 no.1
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    • pp.6-16
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    • 2024
  • The efficiency of silicon solar cells is approaching a theoretical limit referred to as 'the state of the art'. Consequently, maintaining efficiency is more productive than pursuing improvements the last room for limiting efficiency. One of the primary considerations in silicon module conservation is the occurrence of failures and degradation. Degradation can be mitigated during the cell manufacturing stage, unlike physical and spontaneous failure. It is mostly because the chemical reaction is triggered by the carrier generation of thermal and light injection, an inherent aspect of the solar cell environment. Therefore, numerous researchers and cell manufacturers are engaged in implementing mitigation strategies based on the physical degradation mechanism.

Damage analysis of three-leg jacket platform due to ship collision

  • Jeremy Gunawan;Jessica Rikanti Tawekal;Ricky Lukman Tawekal;Eko Charnius Ilman
    • Ocean Systems Engineering
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    • v.13 no.4
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    • pp.385-399
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    • 2023
  • A collision between a ship and an offshore platform may result in structural damage and closure; therefore, damage analysis is required to ensure the platform's integrity. This paper presents a damage assessment of a three-legged jacket platform subjected to ship collisions using the industrial finite element program Bentley SACS. This study considers two ships with displacements of 2,000 and 5,000 tons and forward speeds of 2 and 6.17 meters per second. Ship collision loads are applied as a simplified point load on the center of the platform's legs at inclinations of 1/7 and 1/8; diagonal bracing is also included. The jacket platform is modelled as beam elements, with the exception of the impacted jacket members, which are modelled as nonlinear shell elements with elasto-plastic material and constant isotropic hardening to provide realistic dented behavior due to ship collision load. The structural response is investigated, including kinetic energy transfer, stress distribution, and denting damage. The simulation results revealed that the difference in leg inclination has no effect on the level of localized denting damage. However, it was discovered that a leg with a greater inclination (1/8) resists structural displacement more effectively and absorbs less kinetic energy. In this instance, the three-legged platform collapses due to the absorption of 27.30 MJ of energy. These results provide crucial insights for enhancing offshore platform resilience and safety in high-traffic maritime regions, with implications for design and collision mitigation strategies.

Development of an AI-based remaining trip time prediction system for nuclear power plants

  • Sang Won Oh;Ji Hun Park;Hye Seon Jo;Man Gyun Na
    • Nuclear Engineering and Technology
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    • v.56 no.8
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    • pp.3167-3179
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    • 2024
  • In abnormal states of nuclear power plants (NPPs), operators undertake mitigation actions to restore a normal state and prevent reactor trips. However, in abnormal states, the NPP condition fluctuates rapidly, which can lead to human error. If human error occurs, the condition of an NPP can deteriorate, leading to reactor trips. Sudden shutdowns, such as reactor trips, can result in the failure of numerous NPP facilities and economic losses. This study develops a remaining trip time (RTT) prediction system as part of an operator support system to reduce possible human errors and improve the safety of NPPs. The RTT prediction system consists of an algorithm that utilizes artificial intelligence (AI) and explainable AI (XAI) methods, such as autoencoders, light gradient-boosting machines, and Shapley additive explanations. AI methods provide diagnostic information about the abnormal states that occur and predict the remaining time until a reactor trip occurs. The XAI method improves the reliability of AI by providing a rationale for RTT prediction results and information on the main variables of the status of NPPs. The RTT prediction system includes an interface that can effectively provide the results of the system.

Geotechnical investigation on causes and mitigation of ground subsidence during underground structure construction (터널 및 지중매설물 시공에 따른 지반함몰 발생 원인 및 대책에 대한 지반공학적 조사 연구)

  • Choi, Shin-Kyu;Back, Seung-Hun;An, Jun-Beom;Kwon, Tae-Hyuk
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.18 no.2
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    • pp.143-154
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    • 2016
  • This study investigated the occurrences, causes, and mitigation of the recent ground subsidence and underground cavity generation events in Korea. Two main causes of ground subsidence are (1) the soil erosion by seepage during tunneling and earth excavation and (2) the damage of underground pipes. The main cause of the soil erosion during tunneling was the uncontrolled groundwater flow. Especially, when excavating soft grounds using a tunnel boring machine (TBM), the ground near TBM operation halt points were found to be the most vulnerable to failure. The damage of underground pipes was mainly caused by poor construction, material deterioration, and differential settlement in soft soils. The ground subsidence during tunneling and earth excavation can be managed by monitoring the outflow of groundwater and eroded soils in construction sites. It is expected that the ground subsidence by the underground pipe damage can be managed or mitigated by life cycle analysis and maintenance of the buried pipes, and by controlling the earth pressure distribution or increasing the bearing capacity at the upper ground of the buried pipes.

A Study on the Flexural Capacity of Reinforced Timber Beams with the Inserting Method of CFRP Plates (탄소섬유판 삽입공법으로 보강된 목재보 휨강도에 관한 연구)

  • Kwon, Ki-Hyuk;Yu, Hye-Ran;Lee, Jin-Hyuk;Choi, Min-Seok
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.1
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    • pp.1-7
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    • 2008
  • When historical or cultural buildings need to be repaired or reinforced, the changes of original features should be minimized, and the strengths of structures should be improved. Among the existing methods to reinforce historical wood structures, the carbon fiber reinforcement polymer (CFRP) installation method is one of the best ones to achieve the afore-mentioned requirements. Therefore, this study aims at investigating the reinforcing effects and failure modes of timber beams reinforced with the inserted CFRP, a part of roof trusses in modern wood structures, and at providing the fundamental test data to estimate the CFRP rein-forced timber beam in the application of this reinforcing method. The primary parameters in this study were the layout and amount of CFRP. It was observed that, when $0.3{\sim}0.7%$ of CFRP were installed, the strengths of reinforced timber beams increased up to 173% compared to its original strength, but their strengthening effects were heavily influenced by the characteristics of timber such as burls. In order to improve the applicability of this strengthening method, fundamental understandings on the characteristics of wood would be necessary, and there would be in need of researches on the non-destructive test for wood structures as well.

A Study on the Reinforcement of Bridge Foundation in the Limestone Cavity (석회암 공동지역의 교량기초 보강에 관한 연구)

  • Lee, Sang-Chul;Ryu, Chang-Yeol;Cho, Kook-Hwan
    • Journal of the Korean Society of Hazard Mitigation
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    • v.11 no.1
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    • pp.51-57
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    • 2011
  • Irregular distributions of limestone cavity in Gang-Won province area may cause unexpected accidents from reduced serviceability or failure of structure. It is requested that an appropriate ground reinforcement method should be used to improve bearing capacity of structure, and the method should also be satisfied with environmental requirements. Among several methods used for foundation constructions in cavity area, Rod Jet Pile(RJP) method has been widely used. While the RJP method was used to improve bearing capacity for the railway bridge foundations, water pollutions of drinking water as well as fishery located adjacent to this project area were occurred. The main reason of the water pollution was cement runoff used in cement mortar during injecting material in RJP method. Laboratory tests were performed to prevent water pollution. The compaction mortar method using low movable material was selected for this project. The quality of water at a fishery adjacent to the site and the compressive strength of cores taken from the construction site were measured. Test results show that the water pollutions was minimized, and the average compressive strength of foundation material was over 5 MPa. As a result of this study, compaction mortar method can be used to ensure the bearing capacity of foundation and to prevent environment pollutions.

Study on collapse mechanism and treatment measures of portal slope of a high-speed railway tunnel

  • Guoping Hu;Yingzhi Xia;Lianggen Zhong;Xiaoxue Ruan;Hui Li
    • Geomechanics and Engineering
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    • v.32 no.1
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    • pp.111-123
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    • 2023
  • The slope of an open cut tunnel is located above the exit of the Leijia tunnel on the Changgan high-speed railway. During the excavation of the open cut tunnel foundation pit, the slope slipped twice, a large landslide of 92500 m3 formed. The landslide body and unstable slope body not only caused the foundation pit of the open cut tunnel to be buried and the anchor piles to be damaged but also directly threatened the operational safety of the later high-speed railway. Therefore, to study the stability change in the slope of the open cut tunnel under heavy rain and excavation conditions, a 3D numerical calculation model of the slope is carried out by Midas GTS software, the deformation mechanism is analyzed, anti-sliding measures are proposed, and the effectiveness of the anti-sliding measures is analyzed according to the field monitoring results. The results show that when rainfall occurs, rainwater collects in the open cut tunnel area, resulting in a transient saturation zone on the slope on the right side of the open cut tunnel, which reduces the shear strength of the slope soil; the excavation at the slope toe reduces the anti-sliding capacity of the slope toe. Under the combined action of excavation and rainfall, when the soil above the top of the anchor pile is excavated, two potential sliding surfaces are bounded by the top of the excavation area, and the shear outlet is located at the top of the anchor pile. After the excavation of the open cut tunnel, the potential sliding surface is mainly concentrated at the lower part of the downhill area, and the shear outlet moves down to the bottom of the open cut tunnel. Based on the deformation characteristics and the failure mechanism of the landslides, comprehensive control measures, including interim emergency mitigation measures and long-term mitigation measures, are proposed. The field monitoring results further verify the accuracy of the anti-sliding mechanism analysis and the effectiveness of anti-sliding measures.

Technical Review on Risk Assessment Methodology for Carbon Marine Geological Storage Systems (이산화탄소 해양 지중저장 시스템에서의 누출 위해성 평가방법에 관한 기술적 검토)

  • Hwang, Jin-Hwan;Kang, Seong-Gil;Park, Young-Gyu
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.13 no.2
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    • pp.121-125
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    • 2010
  • Carbon Capture and Storage (CCS) technology mitigates the emission amount of carbon dioxide into the atmosphere and can reduce green house effect which causes the climate change. Deep saline aquifer or obsolete oil/gas storage etc. in the marine geological structure are considered as the candidates for the storage. The injection and storage relating technology have been interested in the global society, however the adverse effect caused by leakage from the system failure. Even the safety level of the CCS is very high and there is almost no possibility to leak but, still the risk to marine ecosystem of the high concentrated carbon dioxide exposure is not verified. The present study introduces the system and environmental risk assessment methods. The feature, event and process approach can be a good starting point and we found the some possibility from the fault tree analysis for evaluation. From the FEP analysis, we drove the possible scenario which we need to concentrate on the construction and operation stages.

Urban Inundation Analysis by Applying with GIS (GIS를 이용한 도시지역 침수해석)

  • Lee, Chang-Hee;Han, Kun-Yeun;Kim, Ji-Sung
    • Journal of the Korean Association of Geographic Information Studies
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    • v.9 no.2
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    • pp.115-126
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    • 2006
  • The purpose of this study is to develop an urban inundation model using GIS(geographic information system). The model is combining a storm sewer system model and a overland-flow model for the estimation inundation depth in urban area caused by the surcharge of storm sewers. SWMM(storm water management model) was employed to resolve the storm sewer flow and to provide the overflow hydrographs caused by the failure of a drainage system due to the shortage of drainage capacity. The level-pool overland-flow model and DEM based overland-flow model were used to calculate the detail inundation zones and depths due to the surcharge on overland surface. The simulation results can help the decision preventing flood damages by redesigning and enlarging the capacities of storm sewer systems in the inundation-prone areas. The model can also be applied to make the potential inundation area map and establish flood-mitigation measures as a part of the decision support system for flood control authority.

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Seismic mitigation of substation cable connected equipment using friction pendulum systems

  • Karami-Mohammadi, Reza;Mirtaheri, Masoud;Salkhordeh, Mojtaba;Mosaffa, Erfan;Mahdavi, Golsa;Hariri-Ardebili, Mohammad Amin
    • Structural Engineering and Mechanics
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    • v.72 no.6
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    • pp.785-796
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    • 2019
  • Power transmission substations are susceptible to potential damage under seismic excitations. Two of the major seismic failure modes in substation supplies are: the breakage of brittle insulator, and conductor end fittings. This paper presents efficient isolation strategies for seismically strengthening of a two-item set of equipment including capacitive voltage transformer (CVT) adjacent to a Lightning Arrester (LA). Two different strategies are proposed, Case A: implementation of base isolation at the base of the CVT, while the LA is kept fixed-base, and Case B: implementation of base isolation at the base of the LA, while the CVT is kept fixed-base. Both CVT and LA are connected to each other using a cable during the dynamic excitation. The probabilistic seismic behavior is measured by Incremental Dynamic Analysis (IDA), and a series of appropriate damage states are proposed. Finally, the fragility curves are derived for both the systems. It is found that Friction Pendulum System (FPS) isolator has the potential of decreasing flexural stresses caused by intense ground motions. The research has shown that when the FPS is placed under LA, i.e. Case B (as oppose to Case A), the efficiency of the system is improved in terms of reducing the forces and stresses at the bottom of the porcelain. Several parametric studies are also performed to determine the optimum physical properties of the FPS.