A Bi-Objective Approach for Optimizing the Installation of PATs in Systems of Transmission Mains

This paper proposes the bi‐objective optimization for the installation of pumps operating as turbines (PATs) in systems of transmission mains, which typically operate at steady flow conditions to cater to tanks in the service of water distribution networks. The methodology aims to find optimal solutions in the trade‐off between installation costs and generated hydropower, which are to be minimized and maximized, respectively. While the bi‐objective optimization is carried out by means of a genetic algorithm, an inner optimization sub‐algorithm provides for the regulation of PAT settings. The applications concerned a real Italian case study, made up of nine systems of transmission mains. The methodology proved able to thoroughly explore the trade‐off between the two objective functions, offering solutions able to recover hydropower up to 83 KW. In each system considered, the optimal solutions obtained were postprocessed in terms of long‐life net profit. Due to the large geodesic elevation variations available in the case study, this analysis showed that, in all systems, the optimal solution with the highest value of generated hydropower was the most profitable under usual economic scenarios, with payback periods always lower than 3 years

The Field-Frequency Lock for Fast Field Cycling Magnetic Resonance: From NMR to MRI

Magnetic field stability plays a fundamental role in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) experiments, guaranteeing accuracy and reproducibility of results. While high levels of stabilization can be achieved for standard NMR techniques, this task becomes particularly challenging for Fast Field Cycling (FFC) NMR and MRI, where the main magnetic field is switched to higher or lower levels during the pulse sequence, and field stabilization must be guaranteed within a very short time after switching. Recent works have addressed the problem with rigorous tools from control system theory, proposing a model based approach for the synthesis of magnetic field controllers for FFC-NMR. While an experimental proof of concept has underlined the correctness of the approach for a complete FFC-NMR setup, the application of the novel, model based Field-Frequency Lock (FFL) system to a FFC-MRI scanner requires proper handling of field encoding gradients. Furthermore, the proof of concept work has also stressed how further advances in the hardware and firmware could improve the overall performances of the magnetic field control loop. The main aim of this perspective paper is then discussing the key challenges that arise in the development of the FFL system suitable for a complete MRI scanner, as well as defining possible research directions by means of preliminary, simulated experiments, with the final goal of favoring the development of a novel, model based FFL system for FFC-MRI

Towards a Model-Based Field-Frequency Lock for NMR

Peer reviewedPublisher PD

Programmed cell death 4 (PDCD4) as a novel prognostic marker for papillary thyroid carcinoma

Background: The primary goal of papillary thyroid cancer (PTC) management was to stratify patients at pre- and post-surgical level to identify the small proportion of cases with potentially aggressive disease. Purpose: The aim of our study is to evaluate the possible role of programmed cell death 4 (PDCD4) and BRAF status as prognostic markers in PTC. Patients and methods: We investigate programmed cell death 4 (PDCD4) immunohistochemical expression in 125 consecutive PTCs with median follow-up of 75.3 months (range, 15\u201398 months) to verify the possible correlation between BRAF status and correlate the classical clinicopathological prognostic factors and PTC outcome with PDCD4 expression. To further support the data, miR-21 expression was tested (by quantitative real-time PCR and in situ hybridization) in a different series of 30 cases (15 PTCs BRAFwt and 15 PTCs BRAFV600E). Moreover, we validated our results using TGCA thyroid carcinoma dataset. Results: We found that 59.8% of the patients showed low-grade PDCD4 nuclear expression and low-grade expression correlated with BRAF V600E. Compared with BRAF 15 wild-type tissue samples, a significant miR-21 up-regulation was associated with BRAF V600E mutations. Lowgrade PDCD4 resulted, and was associated with aggressive histological variants, higher cancer size, extra-thyroidal extension, multifocality, lymph-node metastasis and lymph nodal ratio at the diagnosis. Concerning the outcome, the low-grade PDCD4 expression correlated at univariate and multivariate analysis, with lower levels of recurrence-free survival rate (RFS) and with poor outcome. Moreover, there was significant association between BRAF V600E patients with PDCD4 nuclear loss and lower RFS, whilet here was significant association between BRAF wild-type patients with PDCD4 nuclear expression and better outcome. Conclusion: These results showed that PDCD4 could predict PTC outcome and that the sum of PDCD4 and BRAF alterations increases the prognostic power of BRAF mutation alone

Sum-of-delay models for pressure control in Water Distribution Networks

Service pressure control is a powerful tool to reduce leakage and risk of pipe bursts in Water Distribution Networks (WDNs). However, to obtain good control performances, it is essential to rely on a good model of the plant. A typical approach consists of the identification of a linear, local model of the system around the desired working point. Previous works relied on black-box, high order models to demonstrate that WDNs are characterised by a very complex dynamic behaviour, which should be properly modelled to avoid stability issues resulting from poor regulator design. This work aims at providing a physical justification for such complex dynamic behaviour, by means of a particular grey-box model structure, with pure delays as its fundamental blocks. Moreover, this works demonstrates that the new model structure can be very effective and efficient in modelling the WDN dynamics. Finally, to proper exploit the new model, this work proposes a bi-objective optimisation based procedure for the regulator design. The potentialities of both model identification and regulator design phases are assessed by means of simulated experiments performed on a detailed unsteady flow model of three different WDNs

The Field-Frequency Lock for Fast Field Cycling Magnetic Resonance: From NMR to MRI

Magnetic field stability plays a fundamental role in Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) experiments, guaranteeing accuracy and reproducibility of results. While high levels of stabilization can be achieved for standard NMR techniques, this task becomes particularly challenging for Fast Field Cycling (FFC) NMR and MRI, where the main magnetic field is switched to higher or lower levels during the pulse sequence, and field stabilization must be guaranteed within a very short time after switching. Recent works have addressed the problem with rigorous tools from control system theory, proposing a model based approach for the synthesis of magnetic field controllers for FFC-NMR. While an experimental proof of concept has underlined the correctness of the approach for a complete FFC-NMR setup, the application of the novel, model based Field-Frequency Lock (FFL) system to a FFC-MRI scanner requires proper handling of field encoding gradients. Furthermore, the proof of concept work has also stressed how further advances in the hardware and firmware could improve the overall performances of the magnetic field control loop. The main aim of this perspective paper is then discussing the key challenges that arise in the development of the FFL system suitable for a complete MRI scanner, as well as defining possible research directions by means of preliminary, simulated experiments, with the final goal of favoring the development of a novel, model based FFL system for FFC-MRI

Unsteady flow modelling of hydraulic and electrical RTC of PATs for hydropower generation and service pressure regulation in WDN

The topic of this paper is the recovery of energy from urban waters, which can be performed in water distribution networks (WDNs) through hydraulically and electrically regulated pumps operating as turbines (PATs). The time-varying operating conditions make real time control (RTC) techniques necessary for adjusting both hydropower generation and service pressure regulation. An unsteady flow model allows simulating the skeletonized layout of a real WDN, and assessing the effectiveness of the RTC. Two control schemes, operating at small and large-time steps, respectively, are presented and compared. The numerical simulations prove the application of the prototype feasible in real WDNs, providing effective hydropower generation and service pressure regulation. While the hydropower produced by the two controllers is similar, the first prevails in terms of closeness of the controlled pressure-head at the critical node to the desired set-point, whereas the second performs better in terms of control cost

A gain scheduling approach to improve pressure control in water distribution networks

Real time pressure control is a common technique adopted to face the problem of leakage reduction in water distribution networks. Recently, in the context of Water 4.0, the spread of wired water distribution networks has opened new possibilities in terms of sensing and communication, resulting in the possibility of adopting higher sampling rates and consequently higher closed-loop bandwidths for the control system. While this could be exploited to improve the performance, it has also drawn the attention of the fundamental question of closed-loop stability, which was seldom considered in a systematic way, especially in the hydraulic community. This works aims to combine some recent results in term of design of frequency domain controllers with a gain scheduling approach, to account and compensate for the main nonlinearities affecting the system under control, and to preserve stability and robustness of the closed-loop in a wide operating region. The approach is validated by means of simulated experiments performed on a detailed dynamic model of the water distribution network. In addition, the gain scheduling approach can improve the overall performance of the control scheme and allows avoiding heavy retuning of the regulator when applied to the nonlinear system

Stability and Robustness of Real-Time Pressure Control in Water Distribution Systems

This paper deals with the fundamental requirement of stability of real-time control algorithms for water distribution systems. Loss of stability may in fact generate strong pressure waves that cause damages to the structure and increase leakage and maintenance costs. In addition, since the system under control is characterized by complex, nonlinear dynamic behavior, it is very important to guarantee that stability is preserved even when the water distribution system is working very far from its nominal working point. The aim of this work is therefore to apply tools and methodologies of control system theory to analyze both nominal and robust stability of real-time control algorithms in a case study framework. This allows quantitative understanding of the cause of possible instability of the control scheme and suggests how to prevent it. Finally, this work proposes a possible way to improve the design of the control algorithms under investigation, to reduce the risk of instability events, and, at the same time, reduce the cost of control

The in situ approach to model identification and control design for pressure regulation in Water Distribution Networks: An in silico evaluation

In the context of Water Distribution Networks, service pressure regulation is an important technique that allows reductions in leakage, risk of pipe bursts and mechanical stress to the infrastructure. Recent works demonstrated in silico, i.e. numerically, that linear control systems can be effectively adopted for this task, provided that a careful tuning is performed. Specifically, the tuning should be based on high order, linear models, which describe the system dynamics around a nominal working point. These models can be straightforwardly derived in a simulated environment, but their in situ identification may be challenging due to the presence of non-measurable, exogenous disturbances. This work moves a step forward towards the application of service pressure regulation in situ, by proposing an effective model identification approach for the linear models, based on spectral analysis. The novel approach can cope with exogenous, non-measured disturbances acting during the identification experiments, and considers possible constraints limiting the experimental design. Moreover, the models identified in the in situ conditions are exploited to synthesise linear regulators and assess the closed-loop performances of the overall control methodology. Though being presented and tested in silico, this work assumes a strong practical relevance in view of the results achieved. It in fact demonstrates that novel control schemes, previously designed in nominal conditions only, can be actually designed and implemented in a real scenario, thus making pressure control safer, more reliable and more effective. Finally, the numerical analysis allows for a comparison of both identification and control results with to those obtained in nominal conditions, to provide further insight and stress the reliability of the proposed methodology