New indices for reliability assessment of water distribution networks

This paper presents new indices to evaluate the reliability of water distribution networks (WDNs) usable in the design, planning and management of these networks. Since the pressure-driven analysis (PDA) of WDNs produces more accurate results than the demand-driven analysis, the new indices are proposed based on the PDA. In the proposed measures, nodal pressures, nodal available discharges and the energy loss per unit length of pipes are considered as the main factors influencing the reliability of WDNs. The introduced network reliability index is a combination of two indices named total nodal reliability and total pipe reliability. These indices are equal to the weighted average of all of the nodal and pipe reliabilities, respectively. A sample network is used to evaluate the new proposed index and some of the available indices and to compare their efficiencies in assessing the reliability of WDNs. The results show that the new proposed index is more efficient and outperforms the others. The introduced index is normalized and is independent of the WDN size. This index considers the qualitative aspects of WDNs besides the hydraulic aspects in evaluating reliability.

Layered Region Based Flow-Sensitive Demand-Driven Alias Analysis

The pointer alias is indispensable for program analysis. Comparing to point-to set, it’s more efficient to formulate the alias as the context free language (CFL) reachability problem. However, the precision is limited to flow-insensitivity. To solve this problem, we propose a flow sensitive, demand-driven analysis algorithm for answering may-alias queries. First the partial single static assignment is used to discriminate the address-taken pointers. Then the order of control flow is encoded in the level linearization code to ease comparison. Finally, the query of alias in demand driven is converted into the search of CFL reachability with feasible flows. The experiments demonstrate the effectiveness of the proposed approach.

Pressure-driven modelling of water distribution systems

This paper presents a novel method to model water distribution systems (WDS) with insufficient pressure. Methods for the prediction of the performance of a WDS with pressure deficiencies are reviewed. The influence of imposed relationships between nodal heads and outflows is assessed and numerical results are given. A Newton-Raphson technique plus line search is employed for solving the governing equations. It is demonstrated that the approach offers superior results for the hydraulic performance of networks under abnormal operating conditions compared to demand-driven analysis-based models.

Demand-Driven Data Flow Analysis for Communication Optimization

Exhaustive global array data flow analysis for communication optimization is expensive and considered to be impractical for large programs. This paper proposes a demand-driven analysis approach that reduces the analysis cost by computing only the data flow information related to optimizations. In addition, the analysis cost of our scheme can be effectively managed by trading space for time or compromising precision for time.