Improving partial mutual information-based input variable selection by consideration of boundary issues associated with bandwidth estimation

Abstract not availableXuyuan Li, Aaron C. Zecchin, Holger R. Maie

Experimental verification of pipeline frequency response extraction and leak detection using the inverse repeat signal

Received 3 June 2014; accepted 20 October 2015/Open for discussion until 31 October 2016This paper presents the original design of a side-discharge valve based transient generator that can produce two types of pseudorandom binary signals: a maximum length binary signal and an inverse repeat signal. These two signals are both wide bandwidth, persistent and periodic, but the inverse repeat signal has the advantageous property that it is antisymmetric within each period. The two signals are used to extract the frequency response function of a single water pipeline in the laboratory. The experimental results demonstrate that the frequency response function extracted by the inverse repeat signal is closer to the theoretical linear results as obtained from the transfer matrix method due to it being able to cancel the effect of even-order nonlinearities. The customized transient generator is then applied to a pipeline with a leak. The location of the leak is successfully determined using the first three resonant peaks as extracted by the inverse repeat signal.Jinzhe Gong, Martin F. Lambert, Aaron C. Zecchin, Angus R. Simpso

Parametric study for an ant algorithm applied to water distribution system optimization

© 2005 IEEE.Much research has been carried out on the optimization of water distribution systems (WDSs). Within the last decade, the focus has shifted from the use of traditional optimization methods, such as linear and nonlinear programming, to the use of heuristics derived from nature (HDNs), namely, genetic algorithms, simulated annealing and more recently, ant colony optimization (ACO), an optimization algorithm based on the foraging behavior of ants. HDNs have been seen to perform better than more traditional optimization methods and amongst the HDNs applied to WDS optimization, a recent study found ACO to outperform other HDNs for two well-known case studies. One of the major problems that exists with the use of HDNs, particularly ACO, is that their searching behavior and, hence, performance, is governed by a set of user-selected parameters. Consequently, a large calibration phase is required for successful application to new problems. The aim of this paper is to provide a deeper understanding of ACO parameters and to develop parametric guidelines for the application of ACO to WDS optimization. For the adopted ACO algorithm, called AS/sub i-best/ (as it uses an iteration-best pheromone updating scheme), seven parameters are used: two decision policy control parameters /spl alpha/ and /spl beta/, initial pheromone value /spl tau//sub 0/, pheromone persistence factor /spl rho/, number of ants m, pheromone addition factor Q, and the penalty factor (PEN). Deterministic and semi-deterministic expressions for Q and PEN are developed. For the remaining parameters, a parametric study is performed, from which guidelines for appropriate parameter settings are developed. Based on the use of these heuristics, the performance of AS/sub i-best/ was assessed for two case studies from the literature (the New York Tunnels Problem, and the Hanoi Problem) and an additional larger case study (the Doubled New York Tunnels Problem). The results show that AS/sub i-best/ achieves the best performance presented in the literature, in terms of efficiency and solution quality, for the New York Tunnels Problem. Although AS/sub i-best/ does not perform as well as other algorithms from the literature for the Hanoi Problem (a notably difficult problem), it successfully finds the known least cost - solution for the larger Doubled New York Tunnels Problem.Aaron C. Zecchin, Angus R. Simpson, Holger R. Maier, and John B. Nixo

Leakage flow noise and related flow pattern in a low-speed axial fan with rotating shroud

The effect of rotational speed and pressure rise on the leakage flow noise radiated by a low-speed axial fan, provided with rotating shroud, has been systematically investigated. The leakage flow noise generally increases with the blade loading, with a trend which is qualitatively independent from the rotational speed but non-monotonic, as its growth is interrupted by local minima. As the loading increases, the SPL spectrum shows important modifications, since the characteristic frequency of the subharmonic narrowband humps related to the leakage noise decreases. The flow in the gap region has been studied by means of PIV measurements taken in the meridional plane. At low blade loading, the leakage flow is restrained close to the rotor ring and, at higher loading, it forms a wide recirculation zone. In the latter conditions, an unsteady flow separation likely takes place in the blade tip region which may be observed in the instantaneous flow field only. Possibly, it is responsible for the observed frequency shift of the humps

Influence of water management on the active root-associated microbiota involved in arsenic, iron and sulfur cycles in rice paddies

In recent years, the role of microorganisms inhabiting rice rhizosphere in promoting arsenic contamination has emerged. However, little is known concerning the species and metabolic properties involved in this phenomenon. In this study, the influence of water management on the rhizosphere microbiota in relation to arsenic dissolution in soil solution was tested. Rice plants were cultivated in macrocosms under different water regimes: continuous flooding, continuous flooding with a 2 weeks-period drainage before flowering and dry soil watered every 10 days. The active bacterial communities in rhizosphere soil and in rhizoplane were characterized by 16S rRNA pyrosequencing. An in-depth analysis of microbial taxa with direct or indirect effects on arsenic speciation was performed and related contribution was evaluated. Continuous flooding promoted high diversity in the rhizosphere, with the plant strongly determining species richness and evenness. On the contrary, under watering the communities were uniform, with little differences between rhizosphere soil and rhizoplane. Arsenic-releasing and arsenite-methylating bacteria were selected by continuous flooding, where they represented 8 % of the total. On the contrary, bacteria decreasing arsenic solubility were more abundant under watering, with relative abundance of 10 %. These values reflected arsenic concentrations in soil solution, respectively 135 \ub5g L-1 and negligible in continuous flooding and under watering. When short-term drainage was applied before flowering, intermediate conditions were achieved. This evidence strongly indicates an active role of the rhizosphere microbiota in driving arsenic biogeochemistry in rice paddies, influenced by water management, explaining amounts and speciation of arsenic often found in rice grains

Instantaneous PIV data related to the leakage flow of a low-speed axial-flow fan with rotating shroud

The present paper is companion to Large-scale unsteady flow structures in the leakage flow of a low-speed axial fan with rotating shroud, Canepa et al., 2019. Two-dimensional PIV has been used in order to investigate the leakage flow in a low-speed fan with rotating shroud at three operating conditions. The reported data are constituted by about 3000 instantaneous meridional velocity fields, which are statistically independent. Each velocity field contains 41 7 55 velocity values deployed on a rectangular grid. In order to allow taking ensemble averages of the data, each velocity field has been assigned to a 4-deg bin in the rotor reference. The data are particularly valuable, since no data of this kind and detail have been made available to the scientific community yet

Bioelectrochemical Nitrogen fixation (e-BNF): Electro-stimulation of enriched biofilm communities drives autotrophic nitrogen and carbon fixation

A new approach to microbial electrosynthesis is proposed, aimed at producing whole biomass from N2 and inorganic carbon, by electrostimulation of complex microbial communities. On a carbon-based conductor under constant polarization ( 120.7\u202fV vs SHE), an electroactive biofilm was enriched with autotrophic nitrogen fixing microorganims and led to biomass synthesis at higher amounts (up to 18 fold), as compared to controls kept at open circuit (OC). After 110\u202fdays, the electron transfer had increased by 30-fold, as compared to abiotic conditions. Metagenomics evidenced Nif genes associated with autotrophs (both Archaea and Bacteria) only in polarized biofilms, but not in OC. With this first proof of concept experiment, we propose to call this promising field \u2018bioelectrochemical nitrogen fixation\u2019 (e-BNF): a possible way to \u2018power\u2019 biological nitrogen fixation, organic carbon storage and soil fertility against desertification, and possibly a new tool to study the development of early prokaryotic life in extreme environments

A study of microbial communities on terracotta separator and on biocathode of air breathing microbial fuel cells

Recently, terracotta has attracted interest as low-cost and biocompatible material to build separators in microbial fuel cells (MFCs). However, the influence of a non-conductive material like terracotta on electroactive microbiological communities remains substantially unexplored. This study aims at describing the microbial pools developed from two different seed inocula (bovine and swine sewage) in terracotta-based air-breathing MFC. A statistical approach on microbiological data confirmed different community enrichment in the MFCs, depending mainly on the inoculum. Terracotta separators impeded the growth of electroactive communities in contact with cathodes (biocathodes), while a thick biofilm was observed on the surface (anolyte-side) of the terracotta separator. Terracotta-free MFCs, set as control experiments, showed a well-developed biocathode, Biocathode-MFCs resulted in 4 to 6-fold higher power densities. All biofilms were analyzed by high-throughput Illumina sequencing applied to 16S rRNA gene. The results showed more abundant (3- to 5-fold) electroactive genera (mainly Geobacter, Pseudomonas, Desulfuromonas and Clostridia MBA03) in terracotta-free biocathodes. Nevertheless, terracotta separators induced only slight changes in anodic microbial communities

A performance comparison of differential evolution and genetic algorithm variants applied to water distribution system optimization

The differential evolution (DE) algorithm has been received some attention recently in terms of water distribution system (WDS) optimization. The DE is potentially becoming an alternative optimization tool for WDS design due to its satisfactory search performance. This paper presents a systematic performance comparison between the DE algorithm and the frequently used genetic algorithms (GAs). Two DE variants and two GA variants are compared in this paper in terms of optimizing the design of WDSs. These include the traditional DE, the dither DE algorithm, the traditional GA and the creeping mutation GA. Two well-known benchmark water distribution case studies are used in this study, which are the New York Tunnels Problem and the Hanoi Problem. The results show that the DE variants significantly outperform the GA variants in terms of both the solution quality and efficiency.Feifei Zheng, Angus R. Simpson and Aaron Zecchi

Performance study of differential evolution with various mutation strategies applied to water distribution system optimization

Differential evolution (DE) is a relatively new optimization technique that has been employed to optimize the design of water distribution systems (WDSs). There are three important operators involved in the use of DE: mutation, crossover and selection. These operators are similar to the commonly used genetic algorithms (GAs). However, DE differs significantly from GAs in that mutation is an important operator for DE, while in contrast, crossover is an important operator for GAs. It has been found that the success of the DE algorithm in solving different mathematical optimization problems crucially depends on the mutation strategy that is used. This paper aims to investigate the relative effectiveness of five frequently used mutation strategies of DE when applied to WDS optimization. The five DE variants with different mutation strategies are applied to two well-known WDS case studies: the New York Tunnels Problem and the Hanoi Problem.Feifei Zheng, Angus R. Simpson and Aaron Zecchi