The Experts below are selected from a list of 9738 Experts worldwide ranked by ideXlab platform
John Dalsgaard Sørensen - One of the best experts on this subject based on the ideXlab platform.
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Reliability Analysis and Risk-Based Methods for Planning of Operation and Maintenance of Offshore Wind Turbines
Volume 9: Offshore Geotechnics; Torgeir Moan Honoring Symposium, 2017Co-Authors: John Dalsgaard SørensenAbstract:Reliability analysis and probabilistic models for wind turbines are considered with special focus on structural components and application for Reliability-based calibration of partial safety factors. The main design load cases to be considered in design of wind turbine components are presented including the effects of the control system and possible faults due to failure of electrical / mechanical components. Considerations are presented on the Target Reliability Level for wind turbine structural components. Application is shown for Reliability-based calibrations of partial safety factors for extreme and fatigue limit states are presented. Operation & Maintenance planning often follows corrective and preventive strategies based on information from condition monitoring and structural health monitoring systems. A Reliability- and risk-based approach is presented where a life-cycle approach is used. An example with wind turbine blades is considered using the NORCOWE reference wind farm.
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Optimal Reliability-based code calibration
Structural Safety, 1994Co-Authors: John Dalsgaard Sørensen, I. B. Kroon, Michael Havbro FaberAbstract:Abstract Calibration of partial safety factors is considered in general, including classes of structures where no code exists beforehand. The partial safety factors are determined such that the difference between the Reliability for the different structures in the class considered and a Target Reliability Level is minimized. Code calibration on a decision theoretical basis is also considered and it is shown how Target Reliability indices can be calibrated. Results from code calibration for rubble mound breakwater designs are shown.
Miguel Sepulcre - One of the best experts on this subject based on the ideXlab platform.
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On the Capacity of 5G NR Grant-Free Scheduling with Shared Radio Resources to Support Ultra-Reliable and Low-Latency Communications.
Sensors, 2019Co-Authors: M. Carmen Lucas-estan, Javier Gozalvez, Miguel SepulcreAbstract:5G and beyond networks are being designed to support the future digital society, where numerous sensors, machinery, vehicles and humans will be connected in the so-called Internet of Things (IoT). The support of time-critical verticals such as Industry 4.0 will be especially challenging, due to the demanding communication requirements of manufacturing applications such as motion control, control-to-control applications and factory automation, which will require the exchange of critical sensing and control information among the factory nodes. To this aim, important changes have been introduced in 5G for Ultra-Reliable and Low-Latency Communications (URLLC). One of these changes is the introduction of grant-free scheduling for uplink transmissions. The objective is to reduce latency by eliminating the need for User Equipments (UEs—sensors, devices or machinery) to request resources and wait until the network grants them. Grant-free scheduling can reserve radio resources for dedicated UEs or for groups of UEs. The latter option is particularly relevant to support applications with aperiodic or sporadic traffic and deterministic low latency requirements. In this case, when a UE has information to transmit, it must contend for the usage of radio resources. This can lead to potential packet collisions between UEs. 5G introduces the possibility of transmitting K replicas of the same packet to combat such collisions. Previous studies have shown that grant-free scheduling with K replicas and shared resources increases the packet delivery. However, relying upon the transmission of K replicas to achieve a Target Reliability Level can result in additional delays, and it is yet unknown whether grant-free scheduling with K replicas and shared resources can guarantee very high Reliability Levels with very low latency. This is the objective of this study, that identifies the Reliability and latency Levels that can be achieved by 5G grant-free scheduling with K replicas and shared resources in the presence of aperiodic traffic, and as a function of the number of UEs, reserved radio resources and replicas K. The study demonstrates that current Fifth Generation New Radio (5G NR) grant-free scheduling has limitations to sustain stringent Reliability and latency Levels for aperiodic traffic.
Ralph Ledbetter - One of the best experts on this subject based on the ideXlab platform.
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A Resilience-Based Methodology for Improved Water Resources Adaptation Planning under Deep Uncertainty with Real World Application
Water Resources Management, 2018Co-Authors: Tom Roach, Zoran Kapelan, Ralph LedbetterAbstract:Resilience of a water resource system in terms of water supply meeting future demand under climate change and other uncertainties is a prominent issue worldwide. This paper presents an alternative methodology to the conventional engineering practice in the UK for identifying long-term adaptation planning strategies in the context of resilience. More specifically, a resilience-based multi-objective optimization method is proposed that identifies Pareto optimal future adaptation strategies by maximizing a water supply system’s resilience (calculated as the maximum recorded duration of a water deficit period over a given planning horizon) and minimizing total associated costs, subject to meeting Target system robustness to uncertain projections (scenarios) of future supply and demand. The method is applied to a real-world case study for Bristol Water’s water resource zone and the results are compared with those derived using a more conventional engineering practice in the UK, utilizing a least-cost optimization analysis constrained to a Target Reliability Level. The results obtained reveal that the strategy solution derived using the current practice methodology produce a less resilient system than the similar costing solutions identified using the proposed resilience driven methodology. At the same time, resilience driven strategies are only slightly less reliable suggesting that trade-off exists between the two. Further examination of intervention strategies selected shows that the conventional methodology encourages implementation of more lower cost intervention options early in the planning horizon (to achieve higher system Reliability) whereas the resilience-based methodology encourages more uniform intervention options sequenced over the planning horizon (to achieve higher system resilience).
Pedro Reviriego - One of the best experts on this subject based on the ideXlab platform.
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Selection of the Optimal Memory Configuration in a System Affected by Soft Errors
IEEE Transactions on Device and Materials Reliability, 2009Co-Authors: Juan Antonio Maestro, Pedro ReviriegoAbstract:The selection of the best memory configuration is a challenge for designers when systems are affected by soft errors. When memory Reliability is an issue and scrubbing is not recommendable, multibit protection codes are one of the available options. In this paper, the Reliability of memories protected with those codes is studied. First, a method to analytically approximate the mean number of events to failure of memories protected with error correction codes capable of handling multiple bit errors is presented and validated through simulation experiments. Then, the selection of the optimal protection code for a given memory configuration in terms of memory size, word length, and Target Reliability Level is analyzed. This selection process is illustrated using a practical case study. The study is then extended to determine, for a given error correcting code, the maximum memory size that would meet a Target Reliability Level. Finally, the effect of the memory word size on the system Reliability is considered by comparing different options. In summary, the proposed methods can be useful for designers when choosing the memory configuration at the system Level for critical applications in which Reliability is a major concern.
M. Carmen Lucas-estan - One of the best experts on this subject based on the ideXlab platform.
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On the Capacity of 5G NR Grant-Free Scheduling with Shared Radio Resources to Support Ultra-Reliable and Low-Latency Communications.
Sensors, 2019Co-Authors: M. Carmen Lucas-estan, Javier Gozalvez, Miguel SepulcreAbstract:5G and beyond networks are being designed to support the future digital society, where numerous sensors, machinery, vehicles and humans will be connected in the so-called Internet of Things (IoT). The support of time-critical verticals such as Industry 4.0 will be especially challenging, due to the demanding communication requirements of manufacturing applications such as motion control, control-to-control applications and factory automation, which will require the exchange of critical sensing and control information among the factory nodes. To this aim, important changes have been introduced in 5G for Ultra-Reliable and Low-Latency Communications (URLLC). One of these changes is the introduction of grant-free scheduling for uplink transmissions. The objective is to reduce latency by eliminating the need for User Equipments (UEs—sensors, devices or machinery) to request resources and wait until the network grants them. Grant-free scheduling can reserve radio resources for dedicated UEs or for groups of UEs. The latter option is particularly relevant to support applications with aperiodic or sporadic traffic and deterministic low latency requirements. In this case, when a UE has information to transmit, it must contend for the usage of radio resources. This can lead to potential packet collisions between UEs. 5G introduces the possibility of transmitting K replicas of the same packet to combat such collisions. Previous studies have shown that grant-free scheduling with K replicas and shared resources increases the packet delivery. However, relying upon the transmission of K replicas to achieve a Target Reliability Level can result in additional delays, and it is yet unknown whether grant-free scheduling with K replicas and shared resources can guarantee very high Reliability Levels with very low latency. This is the objective of this study, that identifies the Reliability and latency Levels that can be achieved by 5G grant-free scheduling with K replicas and shared resources in the presence of aperiodic traffic, and as a function of the number of UEs, reserved radio resources and replicas K. The study demonstrates that current Fifth Generation New Radio (5G NR) grant-free scheduling has limitations to sustain stringent Reliability and latency Levels for aperiodic traffic.