Modelling uncertainty for leak localization in Water Networks

The performance and success of model-based leak localization methods applied to water distribution networks (WDN) highly depends on the uncertainty of the system considered. This work proposes an original method of modeling the effect of uncertainties in these networks. The proposed method is based on the collection of real data in the water network in the absence of leaks. The discrepancy (residual) between the measured data and the one provided by a simulator of the network in normal operation is used to extrapolate the possible residuals in the different leak scenarios. In addition, indicators for assessing the effect of uncertainty in the performance of leak localization methods based on residual correlation analysis are provided. The error in terms of correlation intervals and leak localzation assessment between the proposed approximation and the real one is studied by means a simplified model of the WDN of Hanoi (Vietnam).Postprint (published version

Inventory control of finished goods for the aftermarket

TitanX Engine Cooling is a global supplier of powertrain cooling solutions to commercial vehicles, both for OEMs and the independent aftermarket. The company with annual sales of over 1.6 billion SEK (US$ 192 million) has some 800 employees worldwide. TitanX is headquartered in Gothenburg, Sweden and has manufacturing sites in Sweden, USA, Brazil, China and Mexico. Its manufacturing facilities are designed and operated with a strong and continuous application of lean manufacturing principles, and they perceive themselves as a very flexible supplier. The production sites have a high level of vertical integration, including the manufacturing of key critical components to ensure the highest quality results. The production operations are continuously adjusted to meet variations in customer demand. The vision is to be the number one global supplier of powertrain cooling solutions to the commercial vehicle industry. The facility in Sölvesborg consists of three zones; a raw material warehouse, a shop floor, and a finished goods warehouse. TitanX generally keeps high inventory levels of raw material and finished goods. An important reason for this is the marketing strategy to increase the current market share above 30% of the independent aftermarket for truck engine cooling systems. Therefore, high customer service levels and high efficiency are key performance measures that drive high capacity and stock levels

Comparison of demand pattern calibration in water distribution networks with geographic and non-geographic parameterization

Demands are one of the most uncertain parameters in water distribution network models. A good calibration of the model demands leads to better results when using the model for any purpose. A demand pattern calibration methodology that uses a priori information has been developed for calibrating the behavior of demand groups. In cities, similar demand behaviors are distributed all over the network, contrary to smaller villages where demands are clearly sectorised in residential neighborhoods, commercial zones and industrial sectors. In this work, demand pattern calibration has a final use for leakage detection and isolation. Detecting a leakage in a pattern that covers nodes spread all over the network makes the isolation unfeasible. Besides, demands in the same zone may be more similar due to the common pressure of the area rather than for the type of contract. A demand pattern calibration methodology is applied to a real network with synthetic non-geographic demands for calibrating geographic demand patterns. The results are compared with a previous work where the calibrated patterns were the original non-geographic onesPeer ReviewedPostprint (published version

Uncertainty effect on leak localisation in a DMA

The leak localisation methodologies based on data and models are affected by both uncertainties in the model and in the measurements. This uncertainty should be quantified so that its effect on the localisation methods performance can be estimated. In this paper, a model-based leak localisation methodology is applied to a real District Metered Area using synthetic data. In the generation process of the data, uncertainty in demands is taken into account. This uncertainty was estimated so that it can justify the uncertainty observed in the real measurements. The leak localisation methodology consists, first, in generating the set of possible measurements, obtained by Monte Carlo Simulation under a certain leak assumption and considering uncertainty, and second, in falsifying sets of nodes using the correlation with a leak residual model in order to signal a set of possible leaky nodes. The assessment is done by means of generating the confusion matrix with a Monte Carlo approach.Peer ReviewedPostprint (author's final draft

Modelling uncertainty for leak localization in Water Networks

The performance and success of model-based leak localization methods applied to water distribution networks (WDN) highly depends on the uncertainty of the system considered. This work proposes an original method of modeling the effect of uncertainties in these networks. The proposed method is based on the collection of real data in the water network in the absence of leaks. The discrepancy (residual) between the measured data and the one provided by a simulator of the network in normal operation is used to extrapolate the possible residuals in the different leak scenarios. In addition, indicators for assessing the effect of uncertainty in the performance of leak localization methods based on residual correlation analysis are provided. The error in terms of correlation intervals and leak localzation assessment between the proposed approximation and the real one is studied by means a simplified model of the WDN of Hanoi (Vietnam).Peer ReviewedPostprint (published version

Real-Time Non-Intrusive Assessment of Viewing Distance During Computer Use

Purpose: To develop and test the sensitivity of an ultrasound-based sensor to assess the viewing distance of visual display terminals operators in real-time conditions. Methods: A modified ultrasound sensor was attached to a computer display to assess viewing distance in real time. Sensor functionality was tested on a sample of 20 healthy participants while they conducted four 10-minute randomly presented typical computer tasks (a match-three puzzle game, a video documentary, a task requiring participants to complete a series of sentences, and a predefined internet search). Results: The ultrasound sensor offered good measurement repeatability. Game, text completion, and web search tasks were conducted at shorter viewing distances (54.4 cm [95% CI 51.3-57.5 cm], 54.5 cm [95% CI 51.1-58.0 cm], and 54.5 cm [95% CI 51.4-57.7 cm], respectively) than the video task (62.3 cm [95% CI 58.9-65.7 cm]). Statistically significant differences were found between the video task and the other three tasks (all p < 0.05). Range of viewing distances (from 22 to 27 cm) was similar for all tasks (F = 0.996; p = 0.413). Conclusions: Real-time assessment of the viewing distance of computer users with a non-intrusive ultrasonic device disclosed a task-dependent pattern. (C) 2016 American Academy of OptometryPostprint (author's final draft