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Y. Xie
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In this paper we propose a new parameter called Performance Age and the methodology to quantify it. This parameter provides a solid life cycle performance basis for bridge replacement. It is not only developed to give a new perspective to the replacement decision process, but also to support a strategic network management approach for civil infrastructures. The method draws on the principle that a bridge not necessarily has to be end of life at its estimated technical age, as long as it performs better than its expected use. For a bridge this idea could mean that it can reach a higher age than its assumed design life. We quantify Performance Age concept based on a hierarchical model, which consists of a translation of this expected performance with criteria and indicators. A prototype model was tested for three fixed concrete highway bridges managed by Rijkswaterstaat, an agency of the Dutch Ministry of Infrastructure and Environment. The results of this study show that Performance Age can be a useful parameter to predict the end of life of bridges.
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In this paper we propose a new parameter called Performance Age and the methodology to quantify it. This parameter provides a solid life cycle performance basis for bridge replacement. It is not only developed to give a new perspective to the replacement decision process, but also to support a strategic network management approach for civil infrastructures. The method draws on the principle that a bridge not necessarily has to be end of life at its estimated technical age, as long as it performs better than its expected use. For a bridge this idea could mean that it can reach a higher age than its assumed design life. We quantify Performance Age concept based on a hierarchical model, which consists of a translation of this expected performance with criteria and indicators. A prototype model was tested for three fixed concrete highway bridges managed by Rijkswaterstaat, an agency of the Dutch Ministry of Infrastructure and Environment. The results of this study show that Performance Age can be a useful parameter to predict the end of life of bridges.
In this paper, a novel statistical approach is presented for time-of-arrival (TOA) estimation based on first path (FP) pulse detection using a sub-Nyquist sampling ultra-wide band (UWB) receiver. The TOA measurement accuracy, which cannot be improved by averaging of the received signal, can be enhanced by the statistical processing of a number of TOA measurements. The TOA statistics are modeled and analyzed for a UWB receiver using threshold crossing detection of a pulse signal with noise. The detection and estimation scheme based on the Generalized Likelihood Ratio Test (GLRT) detector, which captures the full statistical information of the measurement data, is shown to achieve accurate TOA estimation and allows for a trade-off between the threshold level, the noise level, the amplitude and the arrival time of the first path pulse, and the accuracy of the obtained final TOA.
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In this paper, a novel statistical approach is presented for time-of-arrival (TOA) estimation based on first path (FP) pulse detection using a sub-Nyquist sampling ultra-wide band (UWB) receiver. The TOA measurement accuracy, which cannot be improved by averaging of the received signal, can be enhanced by the statistical processing of a number of TOA measurements. The TOA statistics are modeled and analyzed for a UWB receiver using threshold crossing detection of a pulse signal with noise. The detection and estimation scheme based on the Generalized Likelihood Ratio Test (GLRT) detector, which captures the full statistical information of the measurement data, is shown to achieve accurate TOA estimation and allows for a trade-off between the threshold level, the noise level, the amplitude and the arrival time of the first path pulse, and the accuracy of the obtained final TOA.
A clock synchronization scheme is crucial for obtaining accuracy in time-based positioning systems. Existing clock synchronization schemes are mostly based on a simplified linear clock model, which unfortunately have a poor long-term synchronization accuracy. Assuming a two-way time transfer protocol, we propose a novel clock synchronization algorithm based on a precise physical clock model to realize joint clock synchronization and propagation delay estimation. The Cramer-Rao lower bound (CRLB) is derived for this clock model and shows that the estimation is asymptotically efficient and converges to the lower bound. For long time spans, this model performs better than a linear clock model.
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A clock synchronization scheme is crucial for obtaining accuracy in time-based positioning systems. Existing clock synchronization schemes are mostly based on a simplified linear clock model, which unfortunately have a poor long-term synchronization accuracy. Assuming a two-way time transfer protocol, we propose a novel clock synchronization algorithm based on a precise physical clock model to realize joint clock synchronization and propagation delay estimation. The Cramer-Rao lower bound (CRLB) is derived for this clock model and shows that the estimation is asymptotically efficient and converges to the lower bound. For long time spans, this model performs better than a linear clock model.