Optimal multi-objective discrete decision making using a multidirectional modified Physarum solver

This paper will address a bio-inspired algorithm able to incrementally grow decision graphs in multiple directions for discrete multi-objective optimization. The algorithm takes inspiration from the slime mould Physarum Polycephalum, an amoeboid organism that in its plasmodium state extends and optimizes a net of veins looking for food. The algorithm is here used to solve multi-objective Traveling Salesman and Vehicle Routing Problems selected as representative examples of multi-objective discrete decision making problems. Simulations on selected test case showed that building decision sequences in two directions and adding a matching ability (multidirectional approach) is an advantageous choice if compared with the choice of building decision sequences in only one direction (unidirectional approach). The ability to evaluate decisions from multiple directions enhances the performance of the solver in the construction and selection of optimal decision sequences

A multidirectional modified Physarum solver for discrete decision making

In this paper, a bio-inspired algorithm able to incrementally grow decision graphs in multiple directions is presented. The heuristic draws inspiration from the behaviour of the slime mould Physarum Polycephalum. In its main vegetative state, the plasmodium, this large single-celled amoeboid organism extends and optimizes a net of veins looking for food. The algorithm is here used to solve classical problems in operations research (symmetric Traveling Salesman and Vehicle Routing Problems). Simulations on selected test cases demonstrate that a multidirectional modied Physarum solver performs better than a unidirectional one. The ability to evaluate decisions from multiple directions enhances the performance of the solver in the construction and selection of optimal decision sequences

Analisi del transitorio di avviamento di un propulsore a perossido d'idrogeno

Il perossido di idrogeno ad alte concentrazioni è una sostanza che decompone spontaneamente secondo una reazione fortemente esotermica che libera ossigeno gassoso e vapor d’acqua. L’estrema lentezza della reazione rende necessaria la presenza di un catalizzatore in grado di incrementare la velocità di reazione senza consumarsi. È dunque intuitivo come lo studio dei letti catalitici, dei materiali catalizzatori e delle possibili configurazioni del catalizzatore siano alla base del disegno e del progetto dei propulsori monopropellenti a perossido di idrogeno. Gli esperimenti condotti da ALTA su prototipi di propulsori monopropellente da 5N a perossido di idrogeno con letti catalitici a sfere hanno mostrato transitori di avviamento relativamente lunghi (20-25s). I requisiti tipici sul ritardo di accensione non dovrebbero superare 1s. Elevati ritardi di accensione possono infatti essere la causa di errori di traiettoria, instabilità del veicolo spaziale, ampio consumo di propellente. Nel presente lavoro di tesi sono stati elaborati dei modelli predittivi e dei codici numerici in ambiente Matlab per l’analisi del transitorio di avviamento di propulsori monopropellente a perossido di idrogeno con letti catalitici a sfere. L’obiettivo era quello di individuare quali parametri fossero la causa del lungo transitorio osservato sperimentalmente. L’estrema complessità nel dover trattare un problema PDE non lineare che coinvolge un flusso bifase liquido+gas+vapore e l’assenza di lavori simili in letteratura ha portato a dover semplificare il problema elaborando un codice numerico quasi-stazionario in cui si trascura la caduta di pressione all’interno del letto catalitico. Da questa analisi si è dedotto che il lungo transitorio di avviamento osservato sperimentalmente è causato da effetti di non adiabaticità. Il riscaldamento delle sfere catalitiche gioca infatti un ruolo fondamentale nella catalizzazione del perossido di idrogeno liquido iniettato nella camera di spinta. Sono così stati individuati i parametri su cui poter operare per ridurre il transitorio di accensione. High concentration hydrogen peroxide decomposes spontaneously with an exothermal reaction that release gaseous oxygen and steam. Catalysts is necessary in order to accelerate the reaction rate because the extremely slow reaction velocity. It is of very importance to investigate catalytic bed configurations and catalytic materials for the design of hydrogen peroxide monopropellant rockets. The experimental activity carried out in ALTA’s laboratories on 5N hydrogen peroxide monopropellant thrusters with sphere’s catalytic beds has shown relatively long start-up transient (20-25s). Typical requirements on ignition delay are under 1s. High ignition delay causes trajectory errors, spacecraft instabilities and wide propellant consumption. In the present work mathematical 1-D models and numerical codes in Matlab for the ignition transient analysis of hydrogen peroxide monopropellant thrusters have been elaborated with the aim of individuate the causes of long experimental transient. The extremely complex non-linear PDEs multiphase liquid+gas+vapour flux-conservative problem forced to simplify the model with a quasi-steady approximation in which catalytic bed pressure drop is neglected. Simulations have shown that non-adiabatic effects are the causes of relatively long ignition transient observed in experiments. Catalytic spheres heating have a fundamental role in hydrogen peroxide catalysis through the bed and key parameters able to reduce ignition delay have been individuated

Development of an Arduino-based electrical impedance tomography system with application to dam internal erosion detection

Electrical Impedance Tomography (EIT) is a technique for the imaging of the electrical properties of conductive materials. In EIT, the spatial distribution of the electrical resistivity or electrical conductivity within a domain is reconstructed using measurements made with electrodes placed at the boundaries of the domain. Data acquisition is typically made by applying an electrical current to the object under investigation using a set of electrodes, and measuring the developed voltage between the other electrodes. The tomographic image is then obtained using an inversion algorithm. This work describes the implementation of a simple and low cost 3D EIT measurement system suitable for laboratory-scale studies. The system was specifically developed for the time-lapse imaging of soil samples subjected to erosion processes during laboratory tests. The tests reproduce the process of internal erosion of soil particles by water flow within a granular media; this process is one of the most common causes of failure of earthen levees and embankment dams. The measurements needed strict requirements of speed and accuracy due to the varying time scale and magnitude of these processes. The developed EIT system consists of a PC which controls I/O cards (multiplexers) through the Arduino micro- controller, an external current generator, a digital acquisition device (DAQ), a power supply and the electrodes. The ease of programming of the Arduino interface greatly helped the implementation of custom acquisition software, increasing the overall flexibility of the system and the creation of specific acquisition schemes and configurations. The system works with a multi-electrode configuration of up to 48 channels but it was designed to be upgraded to an arbitrary large number of electrodes by connecting additional multiplexer cards (> 96 electrodes). The acquisition was optimized for multi-channel measurements so that the overall time of acquisition is dramatically reduced compared to the single channel instrumentation. The accuracy and operation were tested under different conditions. The results from preliminary tests show that the system is able to clearly identify objects discriminated by different resistivity. Furthermore, measurements carried out during internal erosion simulations demonstrate that even small variations in the electrical resistivity can be captured and these changes can be related to the erosion processes

CMB Polarization Systematics, Cosmological Birefringence and the Gravitational Waves Background

Cosmic Microwave Background experiments must achieve very accurate calibration of their polarization reference frame to avoid biasing the cosmological parameters. In particular, a wrong or inaccurate calibration might mimic the presence of a gravitational wave background, or a signal from cosmological birefringence, a phenomenon characteristic of several non-standard, symmetry breaking theories of electrodynamics that allow for \textit{in vacuo} rotation if the polarization direction of the photon. Noteworthly, several authors have claimed that the BOOMERanG 2003 (B2K) published polarized power spectra of the CMB may hint at cosmological birefringence. Such analyses, however, do not take into account the reported calibration uncertainties of the BOOMERanG focal plane. We develop a formalism to include this effect and apply it to the BOOMERanG dataset, finding a cosmological rotation angle $\alpha=-4.3^\circ\pm4.1^\circ$. We also investigate the expected performances of future space borne experiment, finding that an overall miscalibration larger then $1^\circ$ for Planck and $0.2\circ$ for EPIC, if not properly taken into account, will produce a bias on the constraints on the cosmological parameters and could misleadingly suggest the presence of a GW background.Comment: 10 pages, 3 figure

Geographical Indications and Risks of Unsustainability Linked to “Disaffection Effects” in the Dairy Sector

This paper deals with the role of geographical indications (GI) in the dairy sector of Italy, with the purpose of highlighting eventual negative dynamics in the adhesion to the GI by the potential operators of Italy. A negative adhesion to the GI circuit shows a “disaffection effect,” and has relevant implications on sustainability on account of the role of a GI in boosting various dimensions of sustainability (economic, social, environmental). In order to verify the presence of a disaffection effect, an empirical analysis of the actors adhering to the GI dairy sector is carried out. Through the collection of secondary sources from official databases, the paper emphasises a negative trend in the adhesion to the GI dairy sector, which also reveals diversified territorial impacts. More precisely, unlike other sectors, the dairy sector reveals negative dynamics in the operators choosing to adhere to the GI circuits. The results of the analysis address some policy issues and solicit policy action to limit the disaffection effect on GI in the dairy sector

Additional ecological services of CSO-CW besides water treatment: modelling CSO-CW behaviour for urban runoff management

INTRODUCTION Combined sewer overflows (CSOs) have been recognized as a dangerous pollutant source for receiving water bodies, and CSO treatment is hence very important to promote a sustainable development. Constructed wetlands (CWs) are starting to be considered as a viable and eco-sustainable technology to treat CSOs (Meyer et al., 2013). However, CSO-CW provides other ecological services beside to water treatment: (i) urban runoff management, (ii) biodiversity increase, (iii) social services (e.g., recreation). Here we have developed a mathematical model of a real case study to highlight the functioning of CSO-CW as also a flood mitigation system, which promotes an urban runoff management from a post-development (high peak, short duration) back again to a pre-development (low peak, high duration) hydrograph influent to the river (Fletcher et al., 2013). METHODS The experimental case study is located in Gorla Maggiore, Italy (46°N, 9°E). The CSO-CW is composed of: (i) grid and sedimentation tank as first flush primary treatment; (ii) four French-type vertical subsurface flow (VF) CW beds as secondary stage (3840 m2) designed to treat the first flush (up to 640 l s-1); (iii) a free water surface flow (FWS) wetland with multiple roles of tertiary treatment of first flush and also second flush treatment (3174 m2), biodiversity increasing, recreational area, and hydraulic buffer (with a floodable surface area up to 7200 m2). The theoretical hydraulic retention time (HRT) is equal to 36 h. A sampling campaign has been done in 2014 in order to characterise temporal variations of CSO quality and quantity and to assess CW removal performances. The data about water quantity (CSO flow rates continuously registered by an automatic sensor with a sampling frequency of 15 minutes) are here used as input of the mathematical model. The mathematical model simulates the unsaturated water flow in VF beds (Richards equation) and the depth of the ponding layer above the VF surface and in the FWS (mass balance equations). In this way, water outflows from each stage of the CW plant are estimated, and the flood mitigation efficiency of the CW is evaluated for different type of CSO events (i.e., single or multiple average CSO events, high return time CSO event). RESULTS AND DISCUSSION The model results show the good performance of the CSO-CW as flood mitigation system. The single CSO average event (883 m3 over 2.4 hours, with a maximum flow rate of 250 l/s) is satisfactorily laminated: (i) the peak flow is reduced by 95%; (ii) the outflow duration is 21 times longer than the one of the CSO event; (iii) the CW is able to store 95% of the influent volume during the CSO event.The CSO-CW exhibits also performs well for CSO mitigation when a sequence of consecutive CSO average events (up to 5, i.e. the maximum number of consecutive CSO events registered) is considered as shown in Figure 1. In this case, the peak flow is reduced by 53%, the outflow is prolonged 5.7 times compared to the CSO event duration, and 38% of the influent volume is stored during the CSO event. Flood mitigation performances remain high also for events with high return time (equal to 10 years – maximum flow rate: 3.4 m3 s−1, volume: 11497 m3, duration: 4.8 h), for which the FWS behaves as a buffer system storing 71% of the influent volume, in addition to the lower (11%) but not negligible mitigation effect provided by the VF beds. Moreover, the peak flow (86% reduction) and the outflow duration (27 times longer than the CSO event duration) are satisfactorily improved for such 10 year return time events. Fig. 1. Influent and simulated effluent flow rate from CSO-CW treatment for a sequence of 5 consecutive CSO mean events: influent CSO (gray line), VF outflow (dotted line), VF overflow (dashed line), and FWS outflow (continuous line). CONCLUSIONS The results of this modelling study confirm the potential of CWs to behave as flood mitigation systems providing the additional ecological service of sustainable urban runoff management. The selected case study demonstrates how CSO-CW promotes a shift from a post-development (high peak, short duration) to a pre-development (low peak, high duration) hydrograph influent to the river water body

Current Trends in Gelatin-Based Drug Delivery Systems

Gelatin is a highly versatile natural polymer, which is widely used in healthcare-related sectors due to its advantageous properties, such as biocompatibility, biodegradability, low-cost, and the availability of exposed chemical groups. In the biomedical field, gelatin is used also as a biomaterial for the development of drug delivery systems (DDSs) due to its applicability to several synthesis techniques. In this review, after a brief overview of its chemical and physical properties, the focus is placed on the commonly used techniques for the development of gelatin-based micro- or nano-sized DDSs. We highlight the potential of gelatin as a carrier of many types of bioactive compounds and its ability to tune and control select drugs' release kinetics. The desolvation, nanoprecipitation, coacervation, emulsion, electrospray, and spray drying techniques are described from a methodological and mechanistic point of view, with a careful analysis of the effects of the main variable parameters on the DDSs' properties. Lastly, the outcomes of preclinical and clinical studies involving gelatin-based DDSs are thoroughly discussed

High Mass Flux Tests on Catalytic Beds for H2O2 Monopropellant Thruster

The present paper illustrates the results of an experimental campaign carried out using LR-III-106 catalyst developed by ALTA S.p.A. in collaboration with the Chemical Department of Pisa University. The catalytic bed has been integrated into a hydrogen peroxide monopropellant thruster prototype and tested in ALTA’s Green Propellant Rocket Test Facility. Endurance tests on LR-III-106 catalyst had been already performed with the same thruster prototype at a lower mass flux (G≈12 kg/m^2 s): the bed was able to decompose up to 13 kg of 90% hydrogen peroxide, equivalent to 2500 s of thruster continuous operation, exhibiting C-Star efficiency higher than 95%. The tests reported in the present paper have been aimed at investigating the performance of the catalyst and the thruster with a mass flux increased up to 55 kg/m^2 s. The bed has shown high decomposition and propulsive efficiencies, well in excess of 90%. The cold start-up transient has been reduced to about 1 s, one..