Radioisotope production using lasers:From basic science to applications

The discovery of chirped pulse amplification has led to great improvements in laser technology,enabling energetic laser beams to be compressed to pulse durations of tens of femtoseconds and focused to a few micrometers.Protons with energies of tens of MeV can be accelerated using,for instance,target normal sheath acceleration and focused on secondary targets.Under such conditions,nuclear reactions can occur,with the production of radioisotopes suitable for medical application.The use of high-repetition lasers to produce such isotopes is competitive with conventional methods mostly based on accelerators.In this paper,we study the production of^(67)Cu,^(63)Zn,^(18)F,and^(11)C,which are currently used in positron emission tomography and other applications.At the same time,we study the reactions^(10)B(p,α)^(7)Be and^(70)Zn(p,4n)^(67)Ga to put further constraints on the proton distributions at different angles,as well as the reaction^(11)B(p,α)^(8)Be relevant for energy production.The experiment was performed at the 1 PW laser facility at VegaⅢin Salamanca,Spain.Angular distributions of radioisotopes in the forward(with respect to the laser direction)and backward directions were measured using a high purity germanium detector.Our results are in reasonable agreement with numerical estimates obtained following the approach of Kimura and Bonasera[Nucl.Instrum.Methods Phys.Res.,Sect.A 637,164–170(2011)].

Algorithms to Compute the Largest Invariant Set Contained in an Algebraic Set for Continuous-Time and Discrete-Time Nonlinear Systems

In this paper, some computational tools are proposed to determine the largest invariant set, with respect to either a continuous-time or a discrete-time system, that is contained in an algebraic set. In particular, it is shown that if the vector field governing the dynamics of the system is polynomial and the considered analytic set is a variety, then algorithms from algebraic geometry can be used to solve the considered problem. Examples of applications of the method(spanning from the characterization of the stability to the computation of the zero dynamics) are given all throughout the paper.

Synthesis and Photophysical Properties of 9,10-Disubstituted Anthracenes

We report the synthesis and photophysical characterization of four 9,10-disubstituted dipheny-lanthracenes with specific modifications of the model backbone which involve both the 9,10 para substituents at the phenyl rings and the substitution with carbon-carbon triple bonds. The effects of such modifications on the photoluminescence and electroluminescence properties have been investigated on the basis of the diphenylanthracene molecular characteristics and in view of application to light-emitting devices. We have found that the substitution with the carbon-carbon triple bonds at the two 9,10-phenyls noticeably alters the electronic states of the reference molecule, also introducing a certain degree of sensitivity to the phenyl substituents, which improves the tunability of the optical emission. Differently, the 9,10 para substituents produce minor changes in the single-molecule properties, due to the lack of electronic conjugation across the 9,10-phenyls. However, even a single nitro substituent in the phenyl para position produces the formation of excimers, which appreciably reduces the optical quantum efficiency. These properties are maintained in solid-state blends and simple spin-coated bilayer electroluminescent devices have been fabricated.

Classification and Analysis of Tube Hydroforming Processes with Respect to Adaptive FEM Simulations

Tube hydroforming process is a relative new process f or production of structural parts of low weight and high rigidity. The successfu lness of the process depends largely on the a proper selection of loading path w hich is axial feeding distance as related to the applied internal pressure. Due to the complicated nature of plastic deformation, a optimum loading path which w ill guarantee good hydroformed parts free of winkle and fracture has often to be determined by finite element analysis. In order to save trials and errors, adap tive FEM simulation method has been developed. To effectively apply the adaptive simulation method, we have to know the applicability of the method. In this pap er, a classification of tube hydroforming (THF) processes based on sensitivity to loading parameters has been suggested. Characteristics of the classification have been analyzed in terms of failure mode, dominant loading parameters and th eir working windows. It was discussed that the so called pressure dominant THF p rocess is the most difficult process for both simulation in FEM analysis and pra ctical operation in real manufacturing situation. To effectively find out the op timum loading path for pressure dominant THF process, adaptive FEM simulation st rategies are mostly needed.

Compost and Compost Tea Management of Mini Watermelon Cultivations Affects the Chemical, Physical and Sensory Assessment of the Fruits

Compost, rich in plant nutrients, is a readily available fertilizer with beneficial effects on physical, chemical, biochemical and biological properties of the soils. Moreover compost-based treatments can exert protective effects against plant diseases occurrence and/or stimulate an enhanced plant physiological status with improvements in quantity and quality of crop productions. In this study the effects of three different compost-based cropping managements on the productive response and main quality parameters of watermelon fruits were investigated. Treatments, in comparison with the conventional cultivation method, were: soil amendment with an agricultural waste compost (AWC), a municipal waste compost (MWC) and a foliar treatment with a compost tea blend (CTB). The productive responses and colour parameters related to compost treatments did not show significant differences compared to control ones, which reached a total yield of about 10.22 kg·m-2 with a mean weight of 2.74 kg. AWC caused a higher ascorbic acid content with an increase of 50% than conventional treatment, while fruits obtained by CTB showed higher values in firmness and Quality Index than control samples. The analysis of main sugars highlighted that the application of compost as biofertilizer influenced the ratio among fructose, glucose and sucrose with respect to those observed for control fruits.

Microwave Heating of Liquid Foods

A mathematical model has been formulated to describe the heat transfer in liquid foods flowing in circular ducts, subjected to microwave irradiations. Three types of liquids with different rheological behavior are considered: skim milk (Newtonian), apple sauce and tomato sauce as non-New-tonian fluids. Each one can flow with different velocities but always in laminar way. The temperature profiles have been obtained solving the transient momentum and heat equations by numerical resolution using the Finite Element Method. The generation term due to the microwave heating has been evaluated according to Lambert’s law. Dielectric properties are considered to be temperature dependent.

AC ripple on DC voltage:Experimental and theoretical investigation of the impact on accelerated ageing in electrical insulation

With the increasing penetration of DC systems into the high voltage and medium voltage power industry,DC voltage is becoming common for distribution/transmission and to supply different typologies of loads.The allowable extent of AC ripple superimposed to DC,and its effect on insulation ageing,is a long-term discussed topic.The most harmful phenomenon causing extrinsic ageing acceleration and insulation system premature failure is partial discharges(PD);thus,the risk of incepting PD due to AC ripple could become a primary issue for electrical asset equipment reliability.In this work,the impact of AC sinusoidal ripple on insulation system life and reliability is dealt with,considering both intrinsic and extrinsic ageing but focusing on the latter,that is,the PD aspect.Experiments are performed to assess how the jump voltage(due to AC ripple)and the DC component impact on PD activity in terms of amplitude and repetition rate.For the first time,the correlation between the magnitude of jump voltage associated with ripple and PD inception is established,shedding a light on the allowable ripple extent which does not impact significantly on ageing and premature insulation failure.This approach can provide straightforward tools for design specification and ageing inference of insulation systems.

Extension of analytical indicial aerodynamics to generic trapezoidal wings in subsonic flow

Analytical indicial aerodynamic functions are calculated for several trapezoidal wings in subsonic flow, with a Mach number 0.3 Ma 0.7. The formulation herein proposed extends wellknown aerodynamic theories, which are limited to thin aerofoils in incompressible flow, to generic trapezoidal wing planforms. Firstly, a thorough study is executed to assess the accuracy and limitation of analytical predictions, using unsteady results from two state-of-the-art computational fluid dynamics solvers as cross-validated benchmarks. Indicial functions are calculated for a step change in the angle of attack and for a sharp-edge gust, each for four wing configurations and three Mach numbers. Then, analytical and computational indicial responses are used to predict dynamic derivatives and the maximum lift coefficient following an encounter with a one-minus-cosine gust. It is found that the analytical results are in excellent agreement with the computational results for all test cases. In particular, the deviation of the analytical results from the computational results is within the scatter or uncertainty in the data arising from using two computational fluid dynamics solvers. This indicates the usefulness of the developed analytical theories.

Addition of Thermoplastic Starch(TPS)to Binary Blends of Poly(lactic acid)(PLA)with Poly(butylene adipate-co-terephthalate)(PBAT):Extrusion Compounding,Cast Extrusion and Thermoforming of Home Compostable Materials

Development of home compostable materials based on bioavailable polymers is of high strategic interest as they ensure a significant reduction of the environmental footprint in many production sectors.In this work,the addition of thermoplastic starch to binary PLA/PBAT blends was studied.The compounds were obtained by a reactive extrusion process by means of a co-rotating twin screw extruder.Thermomechanical,physical and chemical characterization tests were carried out to highlight the effectiveness of the material design strategy.The compounds were subsequently reprocessed by cast extrusion and thermoforming in order to obtain products suitable for the storage of hot food.The extruded films and the thermoformed containers were further characterized to highlight their thermo-mechanical,physical and chemical properties.Thermo-rheological,mechanical and physical properties of the material and of the cast film were analyzed thoroughly using combined technique as capillary rheometer,MFI,DSC,VICAT/HDT,XRD,FTIR,UV-Vis,SEM,permeability and,lastly,running preliminary chemical inertness and biodegradation tests.Particular attention was also devoted to the evaluation of the thermo-mechanical resistance of the thermoformed containers,where the PLA/PBAT/TPS blends proved to be very effective,also presenting a high disintegration rate in ambient conditions.

Reflecting laser-driven shocks in diamond in the megabar pressure range

In this work we present experimental results on the behavior of diamond at megabar pressure. The experiment was performed using the PHELIX facility at GSI in Germany to launch a planar shock into solid multi-layered diamond samples. The target design allows shock velocity in diamond and in two metal layers to be measured as well as the free surface velocity after shock breakout. As diagnostics, we used two velocity interferometry systems for any reflector(VISARs). Our measurements show that for the pressures obtained in diamond(between 3 and 9 Mbar),the propagation of the shock induces a reflecting state of the material. Finally, the experimental results are compared with hydrodynamical simulations in which we used different equations of state, showing compatibility with dedicated SESAME tables for diamond.

Additive Manufacturing of Ceramics from Liquid Feedstocks

In this review,we summarize the research activities carried out by our research group at the University of Padova on the additive manufacturing of ceramics from liquid feedstocks.Particularly,we evaluate the use of preceramic polymers,geopolymers,and sol-gel solutions.We mainly focus on processing with liquid feedstocks because they have some advantages with respect to slurry-based feedstocks in which powders are present.Particularly,lower viscosity,enhanced transparency,and lack of scattering and sedimentation are advantageous features for vat photopolymerization processes,whereas the absence of particulates reduces clogging problems at the nozzle for extrusion-based processes.Simultaneously,preceramic polymers and geopolymers have some limitations in terms of the range of ceramic compositions that can be obtained;sol-gel solutions are intrinsically unstable,whereas printed objects suffer from drying issues.Nevertheless,we successfully produced high-quality parts using a variety of additive manufacturing techniques,some of which(e.g.,volumetric additive manufacturing)have been proposed for the fabrication of ceramic components for the first time.

Corrigendum to"A comparison between powder flow property testers"[Particuology 32(2017)10-20]

The authors regret to inform the readers that a typo error occurred in the writing of equation(4)of the paper.The correct equation,that was the one used in the calculations presented in the paper.

Oxidation in Ca/K-1144 iron-based superconductors polycrystalline compounds

Iron‐based superconductors(IBSCs)are a class of material under investigation for the development of superconducting wires in the low‐temperature‐high magnetic fields power application.Among the various families of IBSCs,the 1144 CaKFe_(4)As_(4) compound is a promising material able to achieve outstanding superconducting properties with a cheap and simple chemical composition.Oxidation,in these compounds,is considered an obstacle for high intergranular critical current density,J_(c,GB).A study devoted to the evaluation of oxidation phenomena and their effects on the superconducting properties is thus needed in order to fully understand the involved mechanisms.From the evaluation of polycrystalline samples obtained by a mechanochemically assisted synthesis route,a degradation of the critical temperature and critical currents has been observed concurrently with oxygen accumulation at grain boundaries in open porosities.However,the crystalline structure at an atomic level seems not affected,as well as intragranular superconducting properties assessed by means of calorimetric methods.These results suggest that loss of superconducting properties in Ca/K‐1144 compounds following oxidation is significantly associated with the worsening of grain connectivity.

Integrated sources of photon quantum states based on nonlinear optics

The ability to generate complex optical photon states involving entanglement between multiple optical modes is not only critical to advancing our understanding of quantum mechanics but will play a key role in generating many applications in quantum technologies.These include quantum communications,computation,imaging,microscopy and many other novel technologies that are constantly being proposed.However,approaches to generating parallel multiple,customisable bi-and multi-entangled quantum bits(qubits)on a chip are still in the early stages of development.Here,we review recent advances in the realisation of integrated sources of photonic quantum states,focusing on approaches based on nonlinear optics that are compatible with contemporary optical fibre telecommunications and quantum memory platforms as well as with chip-scale semiconductor technology.These new and exciting platforms hold the promise of compact,low-cost,scalable and practical implementations of sources for the generation and manipulation of complex quantum optical states on a chip,which will play a major role in bringing quantum technologies out of the laboratory and into the real world.

Study of geometric parameters for the design of short intakes with fan modelling

The flow over a short intake is characterised by a strong interaction with the fan, that can only be captured when the rotor blades are modelled in the numerical simulations. In this paper, we use a coupled methodology to derive indications about relevant geometric variables affecting the high-incidence operation of an ultra-high bypass ratio turbofan intake with a length-to-diameter ratio of 0.35. By reproducing the effect of the fan through a body force model, we carry out a parametric study of the influence of the contraction ratio and the scarf angle at take-off conditions for a grid of 28 different three-dimensional shapes. The analysis of the selected performance metrics distributions at three angles of attack of 16., 24., and 28. reveals that a contraction ratio higher than 1.20 is needed to avoid separation at high incidence. While for an attached inlet the best performance is found with a moderate scarf angle, in presence of a developed separation the distortion level reduces as the scarf decreases up to negative values. We discuss the correspondence between the distortion indexes and the flow field, highlighting the origin of the detachment for the different geometries, according to the operating condition, and analysing the fan operation in the most distorted case. Finally, we assess the influence of modelling the rotor in the simulations, showing that its suppression effect on the separation at a given incidence depends on the intake geometric features.

High Temperature Creep and Superplasticity in a Mg-Zn-Zr Alloy

Creep and superplasticity were investigated by testing a fine-grained extruded Mg–Zn–Zr magnesium alloy under a wide range of applied stress in the temperature range between 100 and 300 ℃. Grain boundary sliding became the dominating mechanism at 200 ℃, leading to a true superplastic behaviour at 300 ℃, where superplasticity was attained even under relatively high strain rates （5×10-3 s-1 ）. By contrast, for lower temperatures, the straining process was controlled by dislocation climb. A comprehensive model, taking into account the simultaneous operation of the different mechanisms, was developed to describe the strain rate dependence on applied stress.

Correlation of powder flow properties to interparticle interactions at ambient and high temperatures

A combination of a continuum approach and a particleparticle approach to describe the multiscale nature of the mechanical properties of bulk solids may be beneficial to scientific and engineering applica tions. In this paper, a procedure is proposed to estimate the interparticle forces beginning with the bulk flow properties as measured with standardized techniques. In particular, the relationship between inter particle forces and bulk solid tensile strength is adopted based on the microscale approaches of Rumpf （1970） and Molerus （1975）. The flow properties of fluid cracking catalyst （FCC）, corundum and glass bead powders were all characterized with a modified Schulze ring shear cell capable of operating at tempera tures up to 500 ~C. The powder test conditions were selected such that the van der Waals forces were the most significant particleparticle interactions. The model equations describe two cases, in which either elastic or plastic deformation of the contact points is assumed. The results indicate that the model pro vides the correct order of magnitude for the values of the tensile strength when proper values for the mean curvature radius at the contact points are taken into account. A sensitivity analysis for the main parameters in the model was performed. This analysis indicated that the assumption of plastic deforma tion at contact surfaces coupled with a decrease in porosity justified an increase of the tensile strength with consolidation stress. Furthermore, the effect of temperature on the measured flow behavior can be explained as a change in the strength of the material.

Pipeline wax deposition modeling:A sensitivity study on two commercial software

This paper presents the results of a sensitivity study carried out to investigate the performances of two commercial codes,OLGA and LedaFlow,used to model the wax deposition process in pipelines under multiphase flow.Reliable simulations of the phenomenon are essential to properly design pipelines and to adopt cost-effective strategies for prevention and removal of wax deposits,reducing the risks of blockage.The main limit of the available models is that their predictions depend on a number of parameters which are usually adjusted to fit the experimental data obtained from laboratory deposition tests.Since a reliable upscale criterion has not been developed yet,model predictions have been more suitably validated using real field data,reported in literature.The performances of the commercial codes in modelling wax precipitation and deposition have been compared to each other.

A Coupled FEM-BEM Approach for the Solution of the Free-Boundary Axi-Symmetric Plasma Equilibrium Problem

In this paper we present a coupled Finite Element Method–Boundary Element Method(FEM-BEM)approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem.The proposed method,obtained from an improvement of the Hagenow-Lackner coupling method,allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region;the external conductors can be modelled either as 2D or 3D models,according to the problem of interest.The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation,such as Picard,Newton-Raphson and Newton-Krylov,in order to provide a robust and reliable tool,able to handle large-scale problems(e.g.high resolution equilibria).This method has been implemented in the FRIDA code(FReeboundary Integro-Differential Axisimmetric–https://github.om/matteobonotto/FRIDA),together with a suitable Adaptive Integration Technique(AIT)for the computation of the source term.FRIDA has been successfully tested and validated against experimental data from RFX-mod device,and numerical equilibria of an ITER-like device.

Development and application of an innovative tool to automate the process of results extraction from the thermo-hydraulic simulator Olga

This paper presents the development and application of an innovative code to extract in an automated way data from the thermo-hydraulic simulator Olga.The results show that the tool can significantly reduce the time needed for the data extraction procedure and increase the reliability of results due to the fact that there is no more the need of the human operator.Moreover,during the data extraction phase,the Olga code is available for running different simulations allowing to optimize the use of this resource.