Application of artificial neural networks and colored petri nets on earthquake resilient water distribution systems

Water distribution systems are important lifelines and a critical and complex infrastructure of a country. The performance of this system during unexpected rare events is important as it is one of the lifelines that people directly depend on and other factors indirectly impact the economy of a nation. In this thesis a couple of methods that can be used to predict damage and simulate the restoration process of a water distribution system are presented. Contributing to the effort of applying computational tools to infrastructure systems, Artificial Neural Network (ANN) is used to predict the rate of damage in the pipe network during seismic events. Prediction done in this thesis is based on earthquake intensity, peak ground velocity, and pipe size and material type. Further, restoration process of water distribution network in a seismic event is modeled and restoration curves are simulated using colored Petri nets. This dynamic simulation will aid decision makers to adopt the best strategies during disaster management. Prediction of damages, modeling and simulation in conjunction with other disaster reduction methodologies and strategies is expected to be helpful to be more resilient and better prepared for disasters --Abstract, page iv

State-based modelling in hazard identification

The signed directed graph (SDG) is the most commonly used type of model for automated hazard identification in chemical plants. Although SDG models are efficient in simulating the plant, they have some weaknesses, which are discussed here in relation to typical process industry examples. Ways to tackle these problems are suggested, and the view is taken that a state-based formalism is needed, to take account of the discrete components in the system, their connection together, and their behaviour over time. A strong representation for operations and actions is also needed, to make the models appropriate for modelling batch processes. A research prototype for HAZOP studies on batch plants (CHECKOP) is also presented, as an illustration of the suggested approach to modelling

Advanced reliability analysis of polymer electrolyte membrane fuel cells in automotive applications

Hydrogen fuel cells have the potential to dramatically reduce emissions from the energy sector, particularly when integrated into an automotive application. However, there are three main hurdles to the commercialisation of this promising technology; one of which is reliability. Cur- rent standards require an automotive fuel cell to last around 5000 h of operation (equivalent to around 150,000 miles), which has proven difficult to achieve to date. This hurdle can be overcome through in-depth reliability analysis including techniques such as Failure Mode and Effect Analysis (FMEA), Fault Tree Analysis (FTA) and Petri-net simulation. This research has found that the reliability field regarding hydrogen fuel cells is still in its infancy, and needs development, if the current standards are to be achieved. In this research, a detailed reliability study of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) is undertaken. The results of which are a qualitative and quantitative analysis of a PEMFC. The FMEA and FTA are the most up to date assessments of failure in fuel cells developed using a comprehensive literature review and expert opinion. Advanced modelling of fuel cell degradation logic was developed using Petri-net modelling techniques. 20 failure modules were identfied that represented the interactions of all failure modes and operational parameters in a PEMFC. Petri-net simulation was used to overcome key pitfalls observed in FTA to provide a verfied degradation model of a PEMFC in an automotive application, undergoing a specific drive cycle, however any drive cycle can be input to this model. Overall results show that the modeled fuel cell's lifetime would reach 34 hours before falling below the industry standard degradation rate of more than 5%. The degradation model has the capability to simulate fuel cell degradation under any drive cycle and with any operating parameters. A fuel cell test rig was also developed that was used to verify the simulated degradation. The rig is capable of testing single cells or stacks from 0-470W power. The results from the verification experimentation agreed strongly with the degradation model, giving confidence in the accuracy of the developed Petri-net degradation model. This research contributes greatly to the field of reliability of PEMFCs through the most up-to-date and comprehensive FMEA and FTA presented. Additionally, a degradation model based upon Petri-nets is the first degradation model to encompass a 1D performance model to predict fuel cell life time under specific drive cycles

Optimal trajectory generation for Petri nets

Recently, the increasing complexity of IT systems requires the early verification and validation of the system design in order to avoid the costly redesign. Furthermore, the efficiency of system operation can be improved by solving system optimization problems (like resource allocation and scheduling problems). Such combined optimization and validation, verification problems can be typically expressed as reachability problems with quantitative or qualitative measurements. The current paper proposes a solution to compute the optimal trajectories for Petri net-based reachability problems with cost parameters. This is an improved variant of the basic integrated verification and optimization method introduced in [11] combining the efficiency of Process Network Synthesis optimization algorithms with the modeling power of Petri nets

A bibliography on formal methods for system specification, design and validation

Literature on the specification, design, verification, testing, and evaluation of avionics systems was surveyed, providing 655 citations. Journal papers, conference papers, and technical reports are included. Manual and computer-based methods were employed. Keywords used in the online search are listed

Microplastics in urban stormwater systems of Western Sydney

This study assessed the extent of microplastic (MP) pollution in the stormwater catchments of Western Sydney. Studies on microplastics in Australian stormwater systems and the lack of generally accepted methods for sample collection and the isolation and quantification of microplastics, were identified as opportunities for exploration. One of the objectives of this study was to identify and develop an acceptable method for separating microplastics from water samples. A novel procedure was developed to collect microplastics by filtering stormwater using a purpose-built single sieve (48.5 μm) mini-filtering device and cascade filtration setup, which included four steel filters with pore sizes of 48.5, 170, 2500 and 5000 μm. Additionally, the six most commonly used microplastic separation methods were selected to assess their organic matter degradation efficiency and polymer degradation potential. This research also presents the first results regarding microplastics pollution in Western Sydney stormwater catchments. Sample collection and analysis were carried out in two steps: preliminary sampling and secondary sampling. Preliminary sampling was carried out in the urban lake of Woodcroft using the mini-filtration device to test the practicality of the pre-identified procedures. Woodcroft and Wattle Grove were selected as the study areas for secondary sampling. Similar microplastics concentrations were observed in secondary sampling for both sites. From a comparison of the data obtained in this study with those in the literature, it was apparent that the stormwater originating from these two urban catchments was considerably contaminated with microplastics. This was attributed to anthropogenic activities in urban areas. Microplastic particles in stormwater can adversely impact aquatic life present in the receiving water bodies. Also, the presence of microplastics could suggest the presence of nanoplastics in urban stormwater. These findings have implications for urban stormwater management and highlight the need for comprehensive and in-depth studies to evaluate micro- and nanoplastics in the inland water bodies of Australia

A network-based system for assessment and management of infrastructure interdependency

Critical infrastructures (CIs) provide services that are essential to both the economy and well-being of nations and their citizens. Over the years, CIs are becoming more complex and interconnected, they are all interdependent in various ways, including logically, functionally, and geographically. The interconnection between CIs results in a very complex and dynamic system which increases their vulnerability to failures. In fact, when an infrastructure is experiencing failures, it can rapidly generate a cascade or domino effect to impact the other infrastructures. Thus, identifying, understanding and modeling infrastructure interdependency is a new field of research that deals with interrelationships between critical infrastructure sectors for disaster management. In the present research project, an integrated network-based analysis system with a user-friendly graphic user interface (GUI) was developed for risk analysis of complex critical infrastructure systems and their component interdependencies, called FCEPN (Fragility Curve and Extended Petri Net analysis). This approach combines: 1) Fragility Curve analysis of the vulnerability of the infrastructure, based on predefined "damage states" due to particular "hazards"; 2) Extended Petri Net analysis of the infrastructure system interdependency to determine the possible failure states and risk values. Two types of Extended Petri Net, Stochastic Petri Net and Fuzzy Petri Net were discussed in this study respectively. The FCEPN system was evaluated using the Bluestone Dam in West Virginia and Huai River Watershed in China as the case studies. Evaluation study results suggested that the FCEPN system provides a useful approach for analyzing dam system design, potential and actual vulnerability of dam networks to flood related impact, performance and reliability of existing dam systems, and appropriate maintenance and inspection work

Criteria and methods for microplastics monitoring in water to be used for human consumption within the new EU legislation framework

Microplastics are ubiquitous contaminants and their release into the environment has long been documented, especially in the last few years. Their widespread presence in several environmental and biological matrices, even in those usually less prone to contamination, have led the regulatory authorities, the scientific community and interested stakeholders to question about possible effects on human health. While the toxicity posed by plastics and microplastics (especially those > 300 µm) to marine organisms seems evident, effects induced by smaller particles on humans are yet to be understood. The main challenge in the identification and toxicological assessments of microplastics rises from the complexity and heterogeneity of these compounds. Regarding microplastics analysis, several different approaches are available. However, the application of different sampling, pre-treatment and analytical methods has resulted in not directly comparable data. In addition, as a consequence of toxicological findings, analytical criteria and matrices investigated are changing. To deal with the increasing levels of plastics and microplastic pollution, the European Commission is adopting a number of actions under the European Green Deal and the Circular Economy Action Plan. In addition, in Directive (EU) 2020/2184 on the quality of water intended for human consumption microplastics appeared for the first time. Described as emerging compounds, microplastics have been related to the “watch list” mechanism introduced with Directive (EU) 2020/2184. The European Commission, by 2024, aims to adopt an analytical method to measure microplastics and, by 2019, to submit a report of risk analysis related to microplastics in drinking water. In order to identify a suitable analytical methodology, the European Commission's Joint Research Centre (JRC) launched a dedicated project in order to harmonize experience and knowledge about microplastic analysis in drinking water, requiring support from national technical-scientific representatives, industry experts and stakeholders. This project includes an online survey and a (series of) workshops designed to collect contribution from stakeholders and experts in microplastics analysis. It is within this complex framework that the present PhD project was structured. This project has multiple purposes, equally divided between the institutional and experimental activities. Institutional activities included the establishment of the Italian National working group on microplastics in drinking water and the discussion on data resulting from the first national survey, based on feedbacks by working group members. The Italian National working group which includes experts from the National Research Council (CNR), national and local environmental Authorities (SNPA: ISPRA and ARPA), Universities and Federation of water suppliers (Utilitalia). The group was designed to work on: (i) JRC and EC support on national expertise about microplastic monitoring in drinking water (ii) development of national analytical method for microplastic in drinking water to be presented to the JRC. From survey data, emerged that experts are flexibly adapting to new challenges posed by microplastics. Regarding experimental activities, specific aims were to develop a method for microplastic analysis suitable for both surface water and water to be used for human consumption, by comparing sampling and analytical techniques, in order to evaluate their pros and cons with a view to a routine approach. Surface water to be used for human for human consumption from the three longest Italian rivers (Po, Adige and Tiber) and water from Drinking Water Treatment Plants (DWTPs) were sampled. For microplastics sampling, a new sampling method, including 2-steps in situ filtration was developed in order to collect several litres of surface water. Assembled filtration system proved to be effective in filtering high volumes of surface water without clogging (average of 1.803,6 L). Tests to assess the goodness of this sampling method for drinking water were also carried out and an average of 2792,6 L litres was filtered without clogging. In order to compare sampling techniques, also water was collected by filling 2.5 L bottles (discrete sampling). Sample pre-treatment and Micro-FTIR analysis were carried out at Istituto di Scienze Polari – Consiglio Nazionale delle Ricerche (ISP-CNR) in Mestre while Micro-Raman analysis were carried out at Department of Chemistry of Padua University. Regarding sample pre-treatment, a “mild” oleo-extraction and purification method was employed. The method has been proved to be adaptable to surface water and efficient to extract microplastics, minimizing any interferers for the analysis. Abundance and polymer identifications were evaluated following the “semi-automated analysis: particle measuring” and “subsampling” approaches in Micro-FTIR. Each IR transmittance spectrum of suspected plastics was then compared with specific microplastics reference libraries. Microplastics were counted, identified and divided by size and shape. For particles between 20 and 100 µm a size range distribution was also performed. Microplastics were observed in every surface water samples collected with both sampling methods, with the exception of the one performed at DWTP #1 with the filtration system, due to inability to properly apply particle measurement to the filters. Microplastics found greatly differed in type and number at each sampling site, while for size distribution and shape greater homogeneity was observed. In terms of polymer composition, heterogeneity was observed, probably due to differences between the various sampling sites. In samples from the filtration systems, polyester, fluorocarbon, polytetrafluoroethylene and acrylic were retrieved in both samples while, in their corresponding discrete samples, only fluorocarbon and polyolefin were common to all sites. Thus, only fluorocarbon was common to all surface water samples. A higher homogeneity was noted by comparing the composition of plastics in filtration system samples with the corresponding discrete samples of the same site. However, only 5 polymers out of 9 (approx. 56%) were common in DWTP #2 and only 5 polymers out of 12 (approx. 42%) were common in DWTP #3. These differences underline the necessity of performing also studies on sampling methods when developing protocols for microplastics analysis, as results may be very different by changing the sampling input. In terms of size, a higher homogeneity was observed. Only approximately 5% of particles found was bigger in size than 100 µm (max 515,9 µm) and approximately 95% of particle size varied between 20 and 100 µm. In any case, particles between 7 µm (LoD) and 20 µm, potentially the most harmful ones, were not retrieved in any samples analyzed with Micro-FTIR. In addition, a detailed dimensional analysis of particles 20 – 100 µm fraction was performed for each sample. Data showed that 40-50 µm size cluster was the most populated for every sample. The 40-50 µm size cluster remained the most populated even if stratifying by sampling techniques and assuming a 1000 L volume for filtration system samples. A general trend in which particles are more condensed in the region to the left of the 60-70 µm cluster can be observed. In terms of shape, a high degree of homogeneity was observed among samples. Non-elongated particles were by far the most common particles (AR < 2) in all samples. The proportion of non-elongated particles over the total remained essentially the same stratifying data for sampling type (approx. 65% for filtration system samples assuming 1000 L as a reference volume and approx. 65% for discrete samples). Raman microscopy analysis was performed on two samples from DWTP #2 and DWTP #3 following the Point and Shoot and Imaging/Mapping approach. Several suspected microplastics were identified with Point and Shoot approach while in Imaging/Mapping a 50x50µm surface area with a 2 µm-spaced grid was mapped. During the Imaging/Mapping, polyvinyl chloride and polyethylene signals (R = 0.53 and R = 0,69), were found in two different points, without any similar signals in the surrounding area. Thus, two suspected microplastics < 2 µm were detected in the sample. Experimental showed that microplastics are present in surface water in significant amounts and have the opportunity to reach DWTPs. Each site showed different polymers composition but small microplastics (SMPs) (especially those non elongated and < 70 µm) proved to be the most abundant group