The Experts below are selected from a list of 80700 Experts worldwide ranked by ideXlab platform
Joaquim Figueiras - One of the best experts on this subject based on the ideXlab platform.
-
design and implementation of a monitoring system applied to a long span prestressed concrete bridge
Structural Concrete, 2011Co-Authors: Helder Sousa, Carlos Felix, Joao Bento, Joaquim FigueirasAbstract:Currently, long-term monitoring systems are mandatory for major civil engineering structures such as bridges, tunnels and dams. Generally, they monitor a set of physical, chemical and mechanical parameters in critical sections of the structure by incorporating appropriate sensors. The set of data collected demonstrates great potential in the prevention of damage and contributes to more Efficient Maintenance of the structures monitored. This work presents the long-term monitoring system installed on the new Leziria Bridge over the River Tagus in Portugal. The system was developed to control some aspects of the construction process and to survey the service life of the structure. A set of structural, durability and environmental parameters defining the bridge condition are remotely assessed in real-time via a fibreoptic network. Aspects such as architecture, installation and functionality of the monitoring system are discussed and the innovative aspects of the implementation are highlighted. In this context, the main goal of this work is to present the long-term monitoring system of Leziria Bridge, sharing the experiences, the solutions and the procedures adopted, given their potential usefulness in the implementation of similar projects. Copyright © 2011 Ernst & Sohn Verlag fur Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
-
design and implementation of a monitoring system applied to a long span prestressed concrete bridge
Structural Concrete, 2011Co-Authors: Helder Sousa, Carlos Felix, Joao Bento, Joaquim FigueirasAbstract:Currently, long-term monitoring systems are mandatory for major civil engineering structures such as bridges, tunnels and dams. Generally, they monitor a set of physical, chemical and mechanical parameters in critical sections of the structure by incorporating appropriate sensors. The set of data collected demonstrates great potential in the prevention of damage and contributes to more Efficient Maintenance of the structures monitored. This work presents the long-term monitoring system installed on the new Leziria Bridge over the River Tagus in Portugal. The system was developed to control some aspects of the construction process and to survey the service life of the structure. A set of structural, durability and environmental parameters defining the bridge condition are remotely assessed in real-time via a fibreoptic network. Aspects such as architecture, installation and functionality of the monitoring system are discussed and the innovative aspects of the implementation are highlighted. In this context, the main goal of this work is to present the long-term monitoring system of Leziria Bridge, sharing the experiences, the solutions and the procedures adopted, given their potential usefulness in the implementation of similar projects. Copyright © 2011 Ernst & Sohn Verlag fur Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.
Jun Yang - One of the best experts on this subject based on the ideXlab platform.
-
boxes Efficient Maintenance of order based labeling for dynamic xml data
International Conference on Data Engineering, 2005Co-Authors: Adam Silberstein, Jun YangAbstract:Order-based element labeling for tree-structured XML data is an important technique in XML processing. It lies at the core of many fundamental XML operations such as containment join and twig matching. While labeling for static XML documents is well understood, less is known about how to maintain accurate labeling for dynamic XML documents, when elements and subtrees are inserted and deleted. Most existing approaches do not work well for arbitrary update patterns; they either produce unacceptably long labels or incur enormous relabeling costs. We present two novel I/O-Efficient data structures, W-BOX and B-BOX that Efficiently maintain labeling for large, dynamic XML documents. We show analytically and experimentally that both, despite consuming minimal amounts of storage, gracefully handle arbitrary update patterns without sacrificing lookup efficiency. The two structures together provide a nice tradeoff between update and lookup costs: W-BOX has logarithmic amortized update cost and constant worst-case lookup cost, while B-BOX has constant amortized update cost and logarithmic worst-case lookup cost. We further propose techniques to eliminate the lookup cost for read-heavy workloads.
-
Efficient Maintenance of materialized top k views
International Conference on Data Engineering, 2003Co-Authors: Jun Yang, Gangqiang Xia, Yuguo ChenAbstract:We tackle the problem of maintaining materialized top-k views. Top-k queries, including MIN and MAX as important special cases, occur frequently in common database workloads. A top-k view can be materialized to improve query performance, but in general it is not self-maintainable unless it contains all tuples in the base table. Deletions and updates on the base table may cause tuples to leave the top-k view, resulting in expensive queries over the base table to "refill" the view. We propose an algorithm that reduces the frequency of refills by maintaining a top-k' view instead of a top-k view, where k' changes at runtime between k and some k/sub max//spl ges/k. We show that in most practical cases, our algorithm can reduce the expected amortized cost of refill queries to O(1) while still keeping the view small. The optimal value of k/sub max/ depends on the update pattern and the costs of querying the base table and updating the view. Compared with the simple approach of maintaining either the top-k view itself or a copy of the base table, our algorithm can provide orders-of-magnitude improvements in performance with appropriate k/sub max/ values. We show how to choose k/sub max/ dynamically to adapt to the actual system workload and performance at runtime, without requiring accurate prior knowledge.
Luca Podofillini - One of the best experts on this subject based on the ideXlab platform.
-
condition based Maintenance optimization by means of genetic algorithms and monte carlo simulation
Reliability Engineering & System Safety, 2002Co-Authors: M Marseguerra, Enrico Zio, Luca PodofilliniAbstract:Abstract Efficient Maintenance policies are of fundamental importance in system engineering because of their fallbacks into the safety and economics of plants operation. When the condition of a system, such as its degradation level, can be continuously monitored, a Condition-Based Maintenance (CBM) policy can be implemented, according to which the decision of maintaining the system is taken dynamically on the basis of the observed condition of the system. In this paper, we consider a continuously monitored multi-component system and use a Genetic Algorithm (GA) for determining the optimal degradation level beyond which preventive Maintenance has to be performed. The problem is framed as a multi-objective search aiming at simultaneously optimizing two typical objectives of interest, profit and availability. For a closer adherence to reality, the predictive model describing the evolution of the degrading system is based on the use of Monte Carlo (MC) simulation. More precisely, the flexibility offered by the simulation scheme is exploited to model the dynamics of a stress-dependent degradation process in load-sharing components and to account for limitations in the number of Maintenance technicians available. The coupled (GA[plus ]MC) approach is rendered particularly Efficient by the use of the ‘drop-by-drop’ technique, previously introduced by some of the authors, which allows to effectively drive the combinatorial search towards the most promising solutions.
Haitao Gao - One of the best experts on this subject based on the ideXlab platform.
-
an Efficient Maintenance optimisation method for series parallel systems using stochastic ordering and revenue difference boundaries
International Conference on Quality Reliability Risk Maintenance and Safety Engineering, 2013Co-Authors: Yifan Zhou, Zhisheng Zhang, Yangqing Bian, Haitao GaoAbstract:A critical problem during the Maintenance optimisation of series-parallel systems is the large strategy space. To address this issue, existing research largely relies on heuristic algorithms, e.g. genetic algorithm (GA) and ant colony optimisation (ACO). These heuristic algorithms can have a low convergence speed, and the obtained strategy are often not global optimal. Instead of searching an optimal strategy in a large space, this paper focuses on the reduction of optimisation space. After investigating the performance dependence among subsystems, this research develops a new strategy space reduction criterion based on the average revenue difference boundaries. By combining the proposed criterion and an earlier method developed by the authors which is based on the stochastic ordering [1], this research develops an Efficient Maintenance optimisation algorithm. The simulation study shows that the developed Maintenance optimisation algorithm can reduce the strategy space more considerably than that proposed in [1].
-
notice of retraction an Efficient Maintenance optimisation method for series parallel systems using stochastic ordering and revenue difference boundaries
International Conference on Quality Reliability Risk Maintenance and Safety Engineering, 2013Co-Authors: Yifan Zhou, Zhisheng Zhang, Yangqing Bian, Haitao GaoAbstract:A critical problem during the Maintenance optimisation of series-parallel systems is the large strategy space. To address this issue, existing research largely relies on heuristic algorithms, e.g. genetic algorithm (GA) and ant colony optimisation (ACO). These heuristic algorithms can have a low convergence speed, and the obtained strategy are often not global optimal. Instead of searching an optimal strategy in a large space, this paper focuses on the reduction of optimisation space. After investigating the performance dependence among subsystems, this research develops a new strategy space reduction criterion based on the average revenue difference boundaries. By combining the proposed criterion and an earlier method developed by the authors which is based on the stochastic ordering [1], this research develops an Efficient Maintenance optimisation algorithm. The simulation study shows that the developed Maintenance optimisation algorithm can reduce the strategy space more considerably than that proposed in [1].
Fangzhou Yin - One of the best experts on this subject based on the ideXlab platform.
-
development of a bridge management system based on the building information modeling technology
Sustainability, 2019Co-Authors: Chunfeng Wan, Zhenwei Zhou, Youliang Ding, Zegang Yang, Yefei Xia, Fangzhou YinAbstract:With the development of the Chinese transportation industry, the number of bridges has increased significantly, but this results in high pressure of structural Maintenance and management. Bridge management system (BMS) is critical for Efficient Maintenance and ensured safety of bridge structures during long-term operation. Building information modeling (BIM) is an emerging technology with powerful visualization and informatization capability, making it an ideal tool for developing modern management systems. This paper introduces the development of a bridge management system based on the BIM technology. Industry Foundation Classes (IFC) and International Framework for Dictionaries (IFD) standards are studied and extended, and coding rules are proposed for the Chinese bridge industry. Also, a standard structural modeling method is proposed to fast build the bridge BIM model. Web-BIM oriented bridge management is proposed, and portable devices are introduced into the system. Collaborative management is realized for different users. The BIM-based Maintenance management system is designed. Finally, a practical BIM-based BMS is established for a long-span cable-stayed bridge in China. This system integrates the BIM with the geographic information system (GIS) and contains information management, inspection management, technical condition evaluation, and enables users to cooperate with each other. Such a BMS could help to improve the management efficiency and ensure its normal operation, providing a useful platform for the Maintenance of massive bridges in China.
