BLOG – prova

News

SPECKLE PATTERN ACQUISITION AND STATISTICAL PROCESSING FOR ANALYSIS OF…

Speckle pattern (SP) is the granular visual pattern that generates when highly coherent optical radiation is shined towards an object with a non-uniform structure (i.e., characterized by irregularities with dimension of the same order of magnitude of the wavelength). If captured by an imaging system, SP images appear as a disorder and chaotic sequence of bright spots and dark regions. However, their statistical properties are highly correlated with the structure of the object that acts as SP source. Traditionally, SP-based techniques have been mainly employed to measure the roughness of surfaces and to study thermal and mechanical properties of solid specimen. However, also fluid suspensions (such as animal and plant-based milks) do generate SP, since they are constituted by scattering elements that float in a surrounding liquid matrix. SP generated by a turbid liquid is particularly challenging to be analysed since suspended particles are subject to Brownian motion and the produced pattern is time-variant. Also, for this reason only very recently, few works (yet very preliminary) are appearing in the scientific literature on the use of SP imaging to investigate turbid liquids.

In this work, the LabEO team has developed a simple low-cost configuration based on a semiconductor laser and a PC-interfaced CMOS camera to acquire SP images generated by irradiating scattering fluids. Whereas, in general in other works, demonstration of the analytical technique has been carried out only on phantom suspensions prepared ad-hoc in the laboratory, samples tested in this work were obtained by water dilution of commercial rice milk that naturally contains lipid micelles acting as scattering particles. After acquisition, SP frames were elaborated to extract statistical parameters that can be correlated with the particulate content. Preliminary results show that the proposed technique allows to easily identify samples with different vegetable milk concentration.

In more detail, the setup investigated at LabEO is low-cost and very simple to be operated: it comprises a semiconductor red laser diode (for SP excitation) and a monochrome CMOS camera (for acquisition of SP images). Light is emitted at the wavelength of 658 nm, with optical power of about 20 mW. The radiation is shined onto a plastic cuvette containing the sample at an angle of about 30° and the camera is placed in front of the sample, at a distance of about 16 cm, making the setup quite compact and suitable to realize a portable sensing system.

Experimental measurements were carried out on nine different suspensions obtained by dilution, with deionized water, of commercial rice milk containing 11 g/L of lipids and 130 g/L of carbohydrates. For every sample tested, 100 SP frames were acquired with the CMOS camera and then processed in MATLAB environment to extract statistical features. For each SP image, expressed as a gray-level matrix of pixels, the average gray-level intensity, the mode and the median were retrieved. It was found that the relationship of these three parameters versus concentration follows a linear behaviour for rice milk concentrations lower than 80% v/v, whereas it tends to saturate for higher concentrations. Such non-linear behaviour can be explained by considering the two counteracting effects. Indeed, when water is added to milk, the concentration of scattering elements decreases, inducing a decrease of the recorded average intensity. On the other hand, by adding water, the refractive index difference between the lipid vesicles (that is around 1.42–1.45 RIU) and the surrounding matrix increases, which would lead to a higher collected intensity. Hence, it was observed that the average gray-level intensity, the mode and the median can be efficiently used for sample distinction only for highly diluted milks.

To extract further information from SP images, the histograms of the gray level distribution were computed and the kurtosis and skewness were retrieved. It was observed that the shape and the characteristics of the histograms depends on the rice milk concentration: in particular, the values of skewness and kurtosis are monotonically increase functions of rice milk concentration. Hence, these two parameters can be used for identifying milk dilutions without ambiguity even when the quantity of added water is smaller than 20% v/v.

In conclusion, this work presents a cost-effective easy-to-use optical setup for identification of turbid samples by means of SP imaging. The presented results are very promising and suggest the possibility of extracting interesting statistical parameters from SP images. Among future perspectives, there is surely the need for investigating more complex statistics (such as gray level co-occurrence matrices and geometrical properties of SP grains) and the interest in applying artificial intelligence tools for the automatic recognition of samples. Since the proposed detection technique is contactless, remote, and label-free, a very interesting application will be the recognition of different types of milk and the identification of their adulteration.

More information on the researches carried out at the Laboratory of ElectroOptics can be found here

References

[1]   V. Bello, E. Bodo and S. Merlo, “Speckle Pattern Acquisition and Statistical Processing for Analysis of Turbid Liquids”, IEEE Transactions on Instrumentation and Measurement, Vol. 72, pp. 1-4, 2023, Art no. 7005004. DOI: 10.1109/TIM.2023.3289543

[2] W. Goodman, “Statistical properties of laser speckle patterns,” in Laser Speckle and Related Phenomena. Berlin, Germany: Springer, 1975, pp. 9–75

[2]  B. M. Oliver, “Sparkling spots and random diffraction,” Proceedings of IEEE, Vol. 51, no. 1, pp. 220–221, 1963

Figure 1: Schematic representation of the optical configuration for SP excitation and acquisition of SP images and of the workflow for extraction of statistical features for identification of rice milk samples.
News

PRELIMINARY THERMAL AND STRUCTURAL ANALYSES ON THE PARABOLIC MIRROR…

A new scientific paper [1] has been published by the UNITUS Nuclear Fusion Research team, concerning the Italian facility “Divertor Tokamak Test” (DTT) [2]. The paper presents a preliminary study about the Parabolic Mirror of the multi-beam transmission line. The design of the mirror has a primary objective: to minimize the temperatures of the mirror and, consequently, the deformation caused by thermal expansion. This is aimed at reducing the impact on the losses in beam transmission efficiency. Various design options, such as materials, body thickness, and cooling solutions, including the shape of cooling channels and water flow, are explored, and discussed.

The mirror is focusing with a parabolic superior surface and has an elliptical shape. The first part of the work is about the realization of the standard CAD model, considering its main characteristics. This kind of structure is subject to the thermal load coming from the absorbed fraction of the microwave beams power, transmitted by eight beams, reflecting on its surface, simultaneously.

Different mirror models are compared. The first option considers an aluminium mirror. The second option is a Stainless-Steel (SS) mirror coupled with a copper layer. Both configurations foresee a simple cooling channel, with elliptical shape and only one turn. Two advanced options include improving the cooling channel, by introducing a cooling channel with a double spiral path, which increases the heat exchange area and allows for better temperature uniformity. An application is on a SS mirror coupled with a copper layer, whilst the second on a pure-copper mirror.
To compare the models evaluating the best performance, thermal and structural analyses have been carried out with ANSYS software and its embedded tool to simulate in a simplified way the water in the cooling channel.

The first results concern the trends of the time evolution of the maximum temperature. They are pairwise similar in two aspects: the reached peak and the cooling rate. The first two configurations with elliptical channel lead to higher peaks and slower cooling, while the spiral channel (third and fourth configurations) to lower peaks and faster cooling. In particular, the design with spiral channel and pure copper has a peak temperature of 55 °C, reduced by ~ 52 %, compared to the first configuration. This decrement of the temperature is good for the structural results. Indeed, from a structural point of view, the comparison of the Z deformation of all the configurations shows that the design in SS-Cu with elliptical channel is the worst solution and the design in pure Cu with spiral channel, has the best structural performance. The main reason is the high thermal conductivity of the copper and the wider heat exchange area possible with the spiral path. The maximum total deformation of this configuration is 0.140 mm, 83% lower than the first configuration (aluminium, with elliptical channel).

Having found the best solution among those proposed, an optimization was done in terms of thicknesses and hydraulic parameters.
The final configuration is a copper mirror with a bulk dug by a double spiral cooling channel, with the addition of a cover layer. The minimum total thickness of the mirror is 2 cm, including 4 mm (minimum thickness) of the cover layer. With an inlet water temperature of 30 °C and a mass flow rate of ~ 10 l/min for both spirals, the maximum temperature on the mirror is ~55 ◦C, recorded at the end time of the pulse of the beams. At the same time, the maximum total deformation is 0.140 mm. Although the highest temperatures occur at the end, the most critical moment in terms of deformation occurs approximately 34 seconds after the pulse begins, when the maximum total deformation reaches a value of 0.177 mm.  The deformed geometry resulting from critical instants will be examined to analyse its impact on the propagation of beams.

References

[1]     Salvitti, Alessandra, et al. “Preliminary thermal and structural analyses on the parabolic mirror of the Multi-Beam Transmission Line of the DTT ECH system.” Fusion Engineering and Design 200 (2024): 114106.

[2]     R. Martone, et al., DTT Divertor Tokamak Test facility Interim Design Report, ENEA (2019).

Figure 1: (Left) Temperature distribution of the last configuration of the mirror. (Right) Detail of the double spiral cooling channel.
News

Inkjet-Printed IDCs for Sensing Applications: Characterization down to Cryogenic…

Interdigitated capacitors (IDCs) have become widely used in several fields ranging from gas sensing to microfluidics thanks to their high sensitivity and wide range of applications. Inkjet printing technology has been proposed as a promising method for fabricating such devices, due to its ability to create complex patterns with high accuracy, thus becoming a valid alternative to traditional fabrication methods.

A recently published research article, which is entitled “Inkjet-Printed Interdigitated Capacitors for Sensing Applications: Temperature-Dependent Electrical Characterization at Cryogenic Temperatures down to 20 K”, details the temperature-dependent electrical properties of inkjet-printed IDCs. The study was the result of a collaborative effort between two Italian research groups: the team led by Prof. Nicola Donato (Res4Net member) from the Department of Engineering at the University of Messina, and the group led by Prof. Silva from the Department of Industrial, Electronics and Mechanical Engineering at Roma Tre University.

The core of the research is the electrical characterization of interdigitated structures, usually employed for sensors development, from room temperature down to cryogenic levels. The research performed provides insights that can be useful in future advancement of the design and optimization of inkjet-printed microwave transducers, particularly in the fields of sensing applications.

The study was recently published in the MDPI Instruments journal and was selected as the cover for Volume 7, Issue 3 (September 2023) of the journal . This highlights the relevance of the article and its contribution to ongoing discussions in the scientific community.

The full version of the article is available here .

News

Parametric FE model for the thermal and hydraulic optimization…

In EU-DEMO reactor, components exposed to burning plasma are subject to extreme conditions due to short and extremely strong thermal transients, which impact their lifetime and functional integrity [1]. Due to this energy, surface vaporization, melting and resolidification may lead to excessive degradation and frequent extraordinary maintenance. For this reason, in view of EU-DEMO and future reactors, one of the most challenging aspects of fusion reactor technology is to design FW (First Wall) sacrificial limiters that will prevent excessive damage of the otherwise un-shadowed FW modules during extreme plasma transients [2]. Rather than dense armors, W-lattice structures can contribute to this purpose, since they can be optimized to have a thermal conductivity that ensures, at steady state, effective heat dissipation and at the same time a thermal diffusivity that, in transients, maximizes the vapor shielding effect [3].

The aim of the UNITUS nuclear fusion research team’s work was to identify, through a parametric model, the optimized component configurations to be considered for this sacrificial limiter, in order to maximize its functional effectiveness [4]. Based on the two elementary cell morphologies developed in previous studies [5], the parametric model allowed to investigate the combinations of relevant parameters, above all component size and geometries, armor/heat sink materials and thicknesses. Thermal optimization regarded both normal operation and two possible transient scenarios: an unmitigated plasma disruption or the Ramp Down phase. By scanning all possible combinations of parameters, those able to provide the best performances thus satisfying the user-defined functional requirements of the limiter were identified.

In detail, through a Matlab code, the possible combinations of relevant parameters were generated. Ansys APDL was used to build the model and perform the thermal analysis on each obtained configuration. The results achieved from the numerical analysis were re-imported into Matlab to verify the suitability of the examined configuration based on the chosen eligibility requirements.

The identification of the possible configurations was followed by a preliminary study through Computational Fluid Dynamics of the thermo-hydraulic behaviour of the PFC cooling circuit. These innovative PFC layouts with tungsten lattices as sacrificial armor material were assumed as input for the analysis of the limiter PFC cooling water circuit in order to verify that the total pressure drop obtained was in line with the tolerable limits required for the potential integration of the limiter cooling circuits within the divertor PHTSs [6].

References

[1]     F. Maviglia, R. Albanese, R. Ambrosino, W. Arter, C. Bachmann, T. Barrett, G. Federici, M. Firdaous, J. Gerardin, M. Kovari, et al., Wall protection strategies for DEMO plasma transients, Fusion Engineering and Design 136 (2018) 410–414

[2]     J. You, C. Bachmann, V. Belardi, M. Binder, D. Bowden, G. Calabro, P. Fanelli, M. Fursdon, I. Garkusha, S. Gerashchenko, et al., Limiters for demo wall protection: Initial design concepts & technology options, Fusion Engineering and Design 174 (2022) 112988

[3]     A. v. Müller, M. Binder, G. Calabro, R. De Luca, P. Fanelli, R. Neu, G. Schlick, F. Vivio, J.-H.  You, Tailored tungsten lattice structures for plasma-facing components in magnetic confinement fusion devices, Materials Today 39 (2020) 146–147.

[4]     Stefanini, C., Fanelli, P., De Luca, R., Paoletti, D., Vivio, F., Belardi, V., … & Neu, R. (2023). Parametric FE model for the thermal and hydraulic optimization of a Plasma Facing Component equipped with sacrificial lattice armours for First Wall limiter application in EU-DEMO fusion reactor. Fusion Engineering and Design, 192, 113604.

[5]     R. De Luca, P. Fanelli, S. Mingozzi, G. Calabro, F. Vivio, F. Maviglia, J. You, Parametric design study of a substrate material for a demo sacrificial limiter, Fusion Engineering and Design 158 (2020) 111721.

[6]     I. Moscato, IDM Report DIV-DEMO.S.1- T011-D002.

Figure 1: Sacrificial component of thermal optimization and CAD model of the two optimized Kelvin cells identified in [5].
Figure 2: 2D thermal optimization procedure.
Figure 3: Simplified process flow diagram.
News

Biomedical Applications of Inkjet Printed Sensors

Inkjet printing (IJP) is an advanced and rapidly evolving technology that employs the deposition of ink droplets onto various types of substrates. This technique has found success with a plethora of substrates (e.g., paper, polyimide, polyethylene terephthalate, plastic, fiberglass, and ceramic) and different kinds of inks, including polymer, metal, and carbon. The remarkable versatility and widespread applicability of IJP enable it to stand out from the other prevalent technologies.

Recent literature has proposed various IJP-based devices for sensing purposes, including sensors for gas, fluid, strain, pressure, temperature, and humidity measurements. Moreover, IJP technology has proven effective in characterizing biological samples, such as cell cultures. In this context, the research group of Prof. Nicola Donato (Res4Net member) from the Department of Engineering, University of Messina, in collaboration with Prof. Cutroneo’s research group from the BIOMORF Department, have recently published their findings on the development of an inkjet printed microwave sensor designed for the contactless dielectric characterization of biological samples. The article is available as open access here.

In their interdisciplinary study, the researchers employed the IJP technique to develop a planar microwave sensor for dielectric characterization of biological samples. The sensor consists of two capacitively coupled split-ring resonators, fabricated using microstrip technology. The proposed prototype is fabricated by printing on an FR4 substrate a silver-based conductive ink. Experimental analysis involved a water-ethanol mixture as a test solution, with varying ethanol volume fractions to alter the mixture dielectric properties. The mixture was placed in a sample vial, arranged on the sensor’s surface, thus eliminating the need for direct contact between the microwave device and the test solution.

The sample permittivity change influences the capacitive coupling between the two split-ring resonators, altering the separation between two resonant frequencies. This unique design enables the sensor to perform differential measurements, thereby improving its robustness.

For the sake of completeness, a lumped-element equivalent-circuit model has been used to estimate and analyze the changes in the values of the lumped elements with ethanol concentration.

Future work will extend the experimental validation to additional liquid mixtures and biological samples, further exploring the sensor capabilities and emphasizing the promising role of inkjet printed sensors in evolving biomedical research.

Photograph of the LDPE sample vial containing the water–ethanol mixture placed over the microwave sensor. 

News

Thermomechanical Analysis of a PFC Integrating W Lattice Armour…

A new scientific paper is published by the UNITUS Nuclear Fusion Research team, concerning a thermomechanical analysis of a plasma facing component (PFC) integrating tungsten lattice armour in response to different plasma scenarios predicted in the EU-DEMO Tokamak [1].
The effective and efficient management of power and particles produced within a tokamak is undoubtedly one of the fundamental steps towards the demonstration of nuclear fusion [2]. PFCs directly facing the plasma are subjected to harsh operating conditions characterised by intense thermal fluxes, erosion, neutron irradiation and sputtering phenomena, which worsen its thermos-structural resistance and deteriorate its functional integrity, ultimately [3]. The need of having sacrificial first wall limiters that are capable of mitigating the effects of such events is mandatory to provide solutions to prevent the excessive damage of the breeding blanket first wall modules in the EU-DEMO fusion reactor, in particular during harsh plasma transients. The integration of tungsten lattices into the architecture of these components can help in meeting their conflictual requirements: a proper morphology of the elementary cell combined with an optimisation of the component design can ensure the effective exhaust of nominal thermal power during normal operation and prompt vapour shielding formation during disruption when thermal decoupling between plasma and heat sink is required. Parametric analyses were conducted on the elementary cell [4] that lead to the identification of two optimised morphologies, (Types A and B). Parametric design analysis based on the use of a 2D model [5] proposed two optimised flat tile configurations in which the complexity of the geometry of the W lattice structure was simplified through a smeared approach: the first one was characterised by Type B W lattice armour, a CuCrZr heat sink and a circular cooling duct, and the second comprised Type A W lattice armour, a heat sink in EUROFER97 and a square duct. In the present work, a detailed 3D model of the two optimised component layouts was set-up, including the complex reticular geometry of the lattice structure, in order to analyse in detail the influence of the actual cellular morphology on the properties of the lattice layer and on the overall performance of the component. The 3D model allowed for performing coupled thermomechanical analyses with regard to the loading conditions that develop during different plasma scenarios and for verifying the structural integrity of the component through acceptance criteria established for ITER in-vessel components (SDC-IC). In particular, the two configurations considered in this study were able to effectively meet the requirements under normal reactor operating conditions (during which the nominal thermal load was in the order of 0.5–1.5 MW/m2 in EU-DEMO), while some requirements were missed in the ramp-down case (when transient heat flux peaks up to 4 MW/m2 were expected). However, the first HHF (high heat flux) tests are about to be performed in order to benchmark the analyses, and dedicated experimental campaigns are ongoing to evaluate the performance of similar components and to allow for a more accurate assessment of their structural integrity under the expected operating conditions [6], [7].

  • Paoletti et al., “Thermomechanical Analysis of a PFC Integrating W Lattice Armour in Response to Different Plasma Scenarios Predicted in the EU-DEMO Tokamak”, Nuclear Engineering 2022, 3, 421-434; 
  • J. H. Donné, “The European roadmap towards fusion electricity,” in Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society Publishing, Mar. 2019.
  • R. Barrett et al., “Progress in the engineering design and assessment of the European DEMO first wall and divertor plasma facing components,” Fusion Engineering and Design, vol. 109, no. 111, pp. 917–924, 2016.
  • de Luca et al., “Parametric design study of a substrate material for a DEMO sacrificial limiter,” Fusion Engineering and Design, vol. 158, no. May, p. 111721, 2020.
  • Stefanini et al., “Parametric FE model for the thermal optimization of a Plasma Facing Component equipped with sacrificial lattice armours for First Wall limiter application in EU-DEMO fusion reactor,” 2022.
  • H. You et al., “Limiters for DEMO wall protection: Initial design concepts & technology options,” Fusion Engineering and Design, vol. 174, Jan. 2022.
  • Mantel et al., “Development and testing of an additively manufactured lattice for DEMO limiters,” Nuclear Fusion, vol. 62, no. 3, Mar. 2022.
Figure 1: Two-dimensional model of the flat tail PFCs subjected to parametric optimisation analysis and the CAD models of Type A and B elementary cells.
Figure 2: Contour plots of temperatures reached in the two optimised PFC layouts during normal reactor operation.
News

First experimental tests on the prototype of a capacitive…

Methodology: In order to design a novel CLS, a first look is given at the conventional cylindrical probe. This is indeed similar to a capacitor with cylindrical armatures, and its capacitance is given by the equation:

where C0 is the dry capacitance, h is the height of the liquid, L is the length of the probe and ε is the dielectric constant of the liquid. From here, the capacitance per unit of length is:

where ε0 is the vacuum/air permittivity, re is the inner radius of the external electrode, Ri is the outer radius of the internal electrode and w is the gap between the electrodes.

It is clear that a way to improve the sensitivity of the sensor is narrowing the gap w. Thus, as explained in [2], narrowing the gap between the two electrodes can make capillarity rise and the communicating vessels phenomenon to happen. The capillarity effect can be numerically modelled and addressed by engraving slits into at least one of the concentric probes so that no column above the bath level can build up in the channel. Two kinds of contour have been considered for the slits: helicoidal and straight. Both were carefully modelled and studied in COMSOL Multiphysics® to calculate the physical characteristics, in particular their sensitivities (Table 1). A third probe, with helicoidal slit on the external probe and the internal probe with no slits was tested too. This will be referred as “mixed”.

The conditioning circuit described in [1] is used for the readout of the prototypes of the probes. It consists in an Integrated Circuit by Texas Instruments that can be interfaced with an Arduino Uno. The sampled data is then processed in MATLAB.

To simulate the oil level change, a stepper motor was used to move the probes with high precision inside and outside of a cylinder full of lubricant oil by Viskoil.

For each sensor, sensitivity, hysteresis, rise time, and root mean square non-linearity error (RMSE) have been studied and evaluated to carry out a comparison.

Hysteresis experiments were done with three immersion and extraction cycles of the probes with increasing pause times between the moving and the sampling phase. The experiments were performed over a full run of 400 mm in 10 mm steps. For each step, after a delay time (if added), 100 samples were taken in a time interval of about 2 s. The mean absolute hysteresis is calculated as the mean of the differences between the immersion and extraction measures. The sensitivity is calculated by fitting the 10 s cycle data with a first-grade polynomial function.

The rise time experiments were performed by measuring the sensor’s output capacitance for a minimum of 20 s, after rapidly dipping or extracting the probe into/from the oil. The time constant 𝜏63 was calculated as 63 % of the time from the moment the sensor stopped to the moment its output capacitance reached its settled value. Settling time was then assumed to be 𝑡𝑟=5∙𝜏63.

The same sampled data were also used to calculate the sensitivity of the sensor and the RMSE, both for the immersion and for the extraction movements.

Results: Table 2 and Figure 1 show some of the obtained results. According to the hysteresis experiment, the sensor with mixed electrodes showed overall the least residual non-linearity. With respect to the rise time evaluation experiments, the main issues arose with the helicoidal probe; in fact, in this case, we observed a very high  time constant since i) the gap between the two electrodes is very narrow and this increases the time needed for the oil to rise and fall in the gap, and ii) the slits are narrow too, allowing a thin membrane of oil to form in them. In this case, the vertical slit electrodes performed best, even though the results are comparable to the mixed electrodes ones. Finally, a preliminary look was given at the dynamic performance of the sensors. The residual non-linearity RMSE is comparable for all three probes. Results for the immersion and extraction are similar too. However, when fitting the sampled data and calculating the sensitivity, a clear difference between the extraction and immersion characteristics arises, with the sensitivity for the immersion being lower than the extraction.

Conclusions: The probes have been prototyped and tested using an in-house developed PC-based mechatronic system and readout electronic. Concerning the sensitivity, the proposed sensor showed an improvement of more than three times with respect to other commercial CLSs. Furthermore, the issue of the second-order response in response to a step change in the oil level was overcome, with an improvement in the settling time too.

References:

[1] Adamo, F.; Attivissimo, F.; de Gioia, S.; Di Nisio, A.; Lotano, D.; Savino, M. “Development and Prototyping of a Capacitive Oil Level Sensor for Aeronautical Applications”, 25th IMEKO TC-4 International Symposium on Measurement of Electrical Quantities, 2022, IMEKO TC-4 2022 and 23rd International Workshop on ADC and DAC Modelling and Testing, IWADC 2022, pp. 330 – 334.

[2] Adamo, F.; Attivissimo, F.; de Gioia, S.; Lotano, D.; Di Nisio, A. “A design strategy for performance improvement of capacitive sensors for in-flight oil-level monitoring aboard helicopters”, Measurement, 2023, 112476, ISSN 0263-2241, DOI: 10.1016/j.measurement.2023.112476.

[3] Adamo, F.; Attivissimo, F.; De Palma, L.; Lotano, D.; Di Nisio, A. “First experimental tests on the prototype of a capacitive oil level sensor for aeronautical applications”, Acta IMEKO, 2023,  ISSN 2221-870X, DOI: 10.21014/actaimeko.v12i1.1474

News

An optimized power conversion system for a stellarator-based nuclear…

A new scientific paper is published by the UNITUS Nuclear Fusion Research team, concerning the optimization of the power conversion system for a stellarator-based nuclear fusion power plant [1].

Unlike all other fusion devices, which are pulsed, the stellarator is inherently steady-state. Thus, it requires a different downstream power conversion system compared to tokamaks. Notably, the authors conceive and optimize such a system for a stellarator power plant, equipped with plasma-facing liquid metal walls in high temperature range (700-900°C). This allows to reach a high power conversion efficiency, due to possible coupling with a CO2 Brayton-Rankine Combined Cycle [2]. Notably, the use of supercritical CO2 for the topping cycle is recommended for high efficiency and low system volume. Following the experience of large scale CC plants, the bottoming cycle is a three pressure superheated steam cycle, with optional re-heating. The system is described through a custom lumped parameter model implemented within MATLAB/Simscape® physical modelling environment. Such a model is preparatory for the optimization via genetic algorithm of the relevant system parameters: the compression ratio of the Brayton cycle and the high, intermediate, and low pressures of the steam turbines.

The efficiency of the power conversion system results 51% and net electrical efficiency of the complete plant (including electrical consumption of reactor auxiliary systems) is 34%. Such figures are remarkably higher compared to the state-of-the-art designs in the field of thermo-nuclear fusion plants, considering that the most optimistic and recent estimate foresee a heat-to-power conversion efficiency of about 34% for tokamak-like reactors. Once the model is validated thanks to the comparison with the results available in the literature for similar systems [2-3], the engineering feasibility, despite the critical components not being market-ready, is discussed. Indeed, the preliminary design of the large-scale supercritical CO2 Gas Turbine and of the compact heat exchanger for the Brayton cycle is successfully carried out.

[1] F. R. Famà et al., “An optimized power conversion system for a stellarator-based nuclear fusion power plant”, Energy Conversion and Management, 276, 116572, 2023. 
[2] S. Segantin et al., “Exploration of power conversion thermodynamic cycles for arc fusion reactor”, Fusion Engineering and Design, 155, 111645, 2020.
[3] B. Zohuri et al., “Advanced nuclear open air-Brayton cycles for highly efficient power conversion”, Nuclear Technology, 192, 1, 48–60, 2015.

7. Figure 1: Schematic of Combined Cycle (CC) featuring three working fluids. shown are the Heat eXchanger (HX), the compressor (c), turbine (t), the superheater (sh), reheater (rh), evaporator (ev), and economizer (eco) at high, intermediate and low pressure (HP, IP, and LP respectively) and condenser (cond).
News

A Combined Approach Using Lorentzian Fitting and ANNs for…

Modeling techniques are crucial in designing microwave devices and help to gain a comprehensive understanding of their operation. In recent years, artificial neural networks (ANNs) have proven successful in modeling the frequency-dependent behavior of various microwave devices such as antennas, sensors, and transistors. ANNs are capable of learning from device behavior through a defined training process and can be used as a fast and accurate model for the description of the device under test. In addition to ANN modeling, the Lorentzian fitting procedure is often used to accurately determine the resonant parameters of microwave resonators. The accurate determination of the resonant frequency and quality factor is desirable regardless of the type of resonator or its application (e.g., filter, sensor). Literature reports suggest that the most accurate estimation of these resonant parameters is obtained by measuring the scattering parameters of the device under test using a vector network analyzer (VNA), followed by fitting a Lorentzian function. This approach compensates for resonator non-idealities, which may affect the accurate determination of both resonant frequency and Q-factor.

In a recent study, the University of Messina (Italy), in collaboration with the University of Niš (Serbia), has developed a new and more reliable modeling tool for studying microwave resonators by combining the Lorentzian fitting method and the ANN-based modeling approach. This approach combines the benefits of both methods and has been successfully applied to model a microwave sensor for relative humidity measurements.

The research, which was co-authored by Prof. Zlatica Marinković from the University of Niš, Dr. Giovanni Gugliandolo, Prof. Giuseppe Campobello, Prof. Giovanni Crupi, and Prof. Nicola Donato (Res4Net member) from the University of Messina, was presented at the 2022 IEEE International Conference on Metrology for eXended Reality, Artificial Intelligence, and Neural Engineering (IEEE MetroXRAINE 2022) and was recognized with the “Best Paper Presented by a Young Researcher” award.

For a more detailed description of the research, please refer to the conference proceeding webpage.

News

Science and communication: the Res4Net experience

Today disciplinary knowledge is fragmented from one another because years and years of sectoral study has led to making each discipline independent.

Everything stems from the crisis that occurred after the Second World War both at a political-economic and cultural level. The goals achieved in all fields ushered in an era of crisis. Society, in an era that was perceived as advanced compared to the modern one, found itself in a climate of insecurity, indifference and the fall of ideals and traditions. Society is in constant motion governed by technological progress which imposes new adaptations every time and leaves behind those who fail to adapt. And it is in this climate that the term “post-modern” is introduced into cultural debates, defining it as something not completely definitive and stable. With the typical urgency of the postmodern age to make the disciplinary fields autonomous and independent, the result of the scientific-cultural and institutional developments of modernity, it has made specialist scientific research necessary and interdisciplinary research almost useless.

The knowledge thus described, however, fails to give an adequate explanation to the phenomena that are studied as the communication between the different disciplines is almost nil due to a forced division and a lack of communication between them. The problem is the language used within each discipline: a specific and technical language functional only to it. The aim that is achieved is a progress of the discipline concerned with scientific rigor, but prevents dialogue with the other areas, which in turn follow the same internal codification. The result is, therefore, an internal coherence, but problematic with the outside. Scientific communication, therefore, must be interdisciplinary to define and contextualize the object of study in reality using a clear language shared by all the disciplines involved in the research and must be transdisciplinary to expand scientific knowledge to a meta-disciplinary level that opens up to the different dimensions of reality through a simple and understandable language also for public opinion in order to legitimize the motivation, the methodological and technological choices and the purpose of the research proposed for the purpose to promote science as a common good necessary for everyone’s life.

In a globalized world, the scientist advertises his work from the beginning, in progress and at the end for two fundamental reasons: to spread scientific knowledge to share and legitimize his work and to seek funding to sponsor his research in order to participate in the construction of a common good, scientific knowledge. Here a paradox emerges: science understood as a common good is forced to promote itself in order to survive in the market of funded projects.

In Italy, for example, the situation is currently fragmented and without any coordination due to the lack of a common data sharing policy. Laws and decrees have regulated state funding for research and education, always resulting insufficient to meet the needs of the scientific world which, where possible, relied on private funding. Even today, scientists and the academic world are asking for more resources to invest in the research needed for new emerging phenomena.

Beyond the choice of strategies, techniques or channels to be used for the dissemination of scientific knowledge or, simply, scientific communication, it is necessary to remember that the information transmitted must have constructive and educational foundations in order to guarantee true emancipation of society because science must be a continuous discovery that helps to resolve and enrich emerging issues by building knowledge that becomes a common good and as such must convey security to those who read and internalize it.

The dissemination of science must become the heritage of everyone, but above all of the new generations.

The Res4Net laboratory network is a concrete example of this new reality in which the main Italian universities and research centers adhere. It proposes itself as a group to think, practice and promote the new scientific communication with particular attention to collaboration and interdisciplinary integration. Members are offered support services for the development of multimedia products and guidance on the effective use of new media. A space on dedicated blogs and social channels is also offered. Res4Net promotes seminars and public debates to stimulate reflection on the theme of new forms of scientific communication. I had the opportunity and the fortune to participate in the realization of this project as an intern at the Politecnico di Milano. My contribution was to offer consultancy on the communicative and digital aspects and the creation of some multimedia materials to be published online on the platform and on the social media involved. My collaboration began in October of the previous year and ended at the end of the academic year. As a person who is growing professionally in the world of communication, I have been able to verify and witness the results of the changes inherent in the ways, times and research objects of today’s science. A sector which, through initiatives such as Res4net, is changing the face of discovery and the goals that man can and must achieve. The involvement of non-experts in the era of globalization is a must and requires an effort of openness and comparison with scientists. The new communication, if used in compliance with the values and social rules that characterize civil societies, can become an invaluable tool for comparison, interdisciplinarity, collaboration and culture.

The greatest result of this project is that it has made the enthusiasm for discovery, interdisciplinarity, collaboration and comparison between experts and not a style of work and life. The process is still in its infancy, the tools and methods of scientific dissemination are still being tested: the communication strategies and the models to be inspired by are constantly changing and, therefore, a constant object of study. The aspiration is to approach a real dialogue. Scientists and the public participate equally in discussions and debates on science and technology topics which can be conducted in different dissemination forms, such as conferences and public forums. A first step has already been taken. On October 27 Res4net participated in the IEEE MetroXRAINE 2022 conference where it was presented and it was possible to compare with other projects in the field of communication. It was possible to observe and learn from those who know more than us.

The results achieved to date are those expected, but certainly in the climate and working style proposed by the Res4net project, the goals to be achieved, even at an international level, will not be long in coming.

In recent months, posts have been published on the site and on social media maintaining common characteristics. Simple texts have been used in the use of semantics and syntax. The terminology used, in fact, is that specific to the sector, but can also be used by less experienced users. The language used is always English to facilitate the international dissemination of information. The choice of layout, images and videos has been studied so that it is captivating and exhaustive to capture the user’s curiosity.

The Res4Net project was born a little over two years ago and is at the beginning of its journey which is in continuous evolution and relationship with the new social and scientific needs that are highlighted in the succession of the passage of time. The universities and research centers involved observe, experiment and verify ever new hypotheses to solve or improve man’s lifestyle.