bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of mesh refinement to relativistic magnetic reconnection
Authors: Jambunathan Revathi , Jones Henry , Corrales Lizzette , Klion Hannah , Rowan Michael E. , Myers Andrew , Zhang Weiqun , Vay Jean-Luc
Published: January 2025

During relativistic magnetic reconnection, antiparallel magnetic fields undergo a rapid change in topology, releasing a large amount of energy in the form of non-thermal particle acceleration. This work explores the application of mesh refinement to 2D reconnection simulations to efficiently model the inherent disparity in length-scales. We have systematically investigated the effects of mesh refinement and determined necessary modifications to the algorithm required to mitigate non-physical artifacts at the coarse–fine interface. We have used the ultrahigh-order pseudo-spectral analytical time-domain Maxwell solver to analyze how its use can mitigate the numerical dispersion that occurs with the finite-difference time-domain (or “Yee”) method. Absorbing layers are introduced at the coarse–fine interface to eliminate spurious effects that occur with mesh refinement. We also study how damping the electromagnetic fields and current density in the absorbing layer can help prevent the non-physical accumulation of charge and current density at the coarse–fine interface. Using a mesh refinement ratio of 8 for two-dimensional magnetic reconnection simulations, we obtained good agreement with the high-resolution baseline simulation, using only 36% of the macroparticles and 71% of the node-hours needed for the baseline. The methods presented here are especially applicable to 3D systems where higher memory savings are expected than in 2D, enabling comprehensive, computationally efficient 3D reconnection studies in the future.
On the nature of hectometric continuum-type emissions in the near-Earth plasma
Authors: Mogilevsky M. M. , Shaposhnikov V. E. , Chernyshov A. A. , Chugunin D. V. , Dorofeev D. A.
Published: January 2025

The ERG (Arase) satellite recently discovered a non-thermal hectometric continuum with a narrowband frequency structure. The mechanism behind the generation of this type of emission in the near-Earth plasma is still unknown. This study examines the potential use of electron cyclotron harmonics instability to explain the line structure of hectometric radio emissions for the first time. By analyzing the case of the non-thermal hectometric continuum, a proposed mechanism for the creation of a quasi-harmonic frequency structure resulting in quasi-parallel emission bands is discussed. In other words, the double plasma resonance effect is suggested as a possible explanation for the observed emission bands in the dynamic spectrum of hectometric radio waves. It is demonstrated that the double plasma resonance mechanism could account for existing measurements of hectometric radiation and explain the presence of the non-thermal hectometric continuum in the near-Earth plasma.
3D Dirac semimetal Cd3As2-based solid solutions growth and characterization
Authors: Arushanov E. , Nateprov A. N. , Cywinski G. , Knap W.
Published: January 2025

Recent advancements in II3V2 semiconducting compounds have garnered significant attention due to their unique electronic properties and potential applications. Materials like Cd3As2 and Cd3As2-based solid solutions, often referred to as three-dimensional analogs of graphene, exhibit intriguing phenomena such as high electron mobility and a Dirac semimetal band structure. This review summarizes recent research progress, covering a broad range of topics including crystal structure analysis, thin film fabrication, band structure studies, and various experimental findings such as classical transport behavior, Shubnikov-de Haas oscillations, magnetization, optical and magneto-optical effects, and electron spin resonance, all within the last three decades. By providing a comprehensive overview of these research areas, this review aims to highlight the current state of understanding and identify promising directions for future research in Cd3As2-based solid solutions.
Dynamics and manipulation of ultrashort laser pulses via plasma shutter
Authors: Wei Wen-Qing , Wang Yu , Ge Xu-Lei , Deng Yan-Qing , Zhang Shi-Zheng , Wan Feng , Li Jian-Xing , Zhao Yong-Tao , Yuan Xiao-Hui
Published: January 2025

The characterization and manipulation of ultrashort high-intensity laser pulses were investigated both numerically and experimentally using an ultrathin foil as plasma shutter. Our work revealed a laser intensity enhancement with a clean and steepened leading edge when the pulse passed through an expanded moderate-density plasma. The fast dynamics of laser–plasma interaction in underdense, transparent, and overdense regimes were elucidated by measuring the temporal-spatial intensity and phase profiles of the transmitted pulses. Key nonlinear effects such as relativistic self-focusing, self-phase modulation, self-induced transparency, and hole-boring were identified as factors influencing laser pulse shaping, with their impact determined by the plasma density. Our approach allows for the robust utilization of the plasma shutter in existing laser facilities without additional requirements. By controlling the spatiotemporal properties of high-power laser pulses, it opens up the possibility for developing compact laser-driven particle accelerators, ultrabright radiation sources, and plasma photonics.
Chemical transport-based growth of Si and SiGe nanowires
Authors: Yang Ke , Zhu Xianjun , Gong Ruiling , Florea Ileana , Roca i Cabarrocas Pere , Chen Wanghua
Published: January 2025

This study investigates the chemical transport-based growth of Si and Ge nanowires (NWs) using plasma-enhanced chemical vapor deposition. We found that Si NW growth requires a high etching temperature of 400 °C, related to a stronger Si–H bond energy compared to the Ge–H bond energy, allowing Ge NWs to form at 250 °C. The growth process is influenced by various parameters, including etching temperature, radio frequency power, GeH4/SiH4 precursor gas ratios, doping, and inter-electrode distance. Optimal Si NW growth is achieved at a substrate temperature of 250 °C during pre-coating and 400 °C during etching, with an RF power of 100 W. Conversely, Ge NWs can be fabricated at 250 °C, although they tend to be smaller and less dense. The study also highlights the role of the doping of the amorphous film precursors, with n-type doping enhancing growth and crystallization, while p-type doping negatively affects NW formation. Key findings include the significance of maintaining optimal etching time and its effect on NW morphology and uniformity. Overall, the results provide a novel method for efficiently growing Si and Ge NWs, emphasizing the importance of carefully controlling growth conditions.
Tip–tilt-decoupled vertical comb-drive micromirror based on a D-SOI wafer and interlayer TSV
Authors: Xia Yuhu , Ling Biyun , Wang Xiaoyue , Wu Yaming
Published: January 2025

Mechanical cross-axis coupling in biaxial scanning increases calibration workload and affects the performance of tip–tilt (TT) micromirror. The integration of gimbal and inner-axis vertical comb-drive (VCD) actuators is a viable design for TT-decoupled micromirrors. The key to developing such a structure is guaranteeing that the integrated inner-axis VCD actuator is insulated from the gimbal and is electrically connected to the substrate while minimizing fabrication difficulty. For this purpose, this paper introduces a double-silicon-on-insulator (D-SOI) wafer with two mutually-insulated device layers into the development of TT-decoupled VCD micromirrors. For both tip and tilt scanning modes, two VC sets in each VCD actuator are arranged on different device layers of the D-SOI wafer. Gimbal, reflective mirrors and springs are fabricated on the identical device layer of the D-SOI wafer, forming an integrated structure together with an inner-axis VCD actuator. In addition, polysilicon-based interlayer through-silicon-vias and surface metal redistribution layers are employed to electrically connect all the driving signals to the wiring substrate. The D-SOI wafer is bonded to the wiring substrate using thermocompression bonding processing before removing the D-SOI handle layer and structure release. Based on the proposed structure and micromachining process, this paper fabricates a 3 × 3 micromirror array (MMA), in which each pixel is 951 × 1096 µm2 in footprint and has a fill factor of 50

%

. Testing results of the fabricated MMA exhibit a quasi-static mechanical tilt/tip angle of 1.266/1.436 ∘ at 35/35 V, and an RMS reflective mirror roughness of 5.323 nm.
Ion momentum mapping in photodissociation and Coulomb explosion events using ion time-of-flight analyzers
Authors: Kukk Edwin
Published: January 2025

Modern light sources such as free electron lasers allow for tracking photoinduced events with an unprecedented accuracy. Ion spectroscopy is a particularly useful tool, revealing, e.g., momentum correlations in dissociation and Coulomb explosion patterns. Determining ion momentae and their relationship with the highest achievable accuracy is therefore very valuable. Here, we develop a systematic approach of accurate ion momentum determination in Wiley-McLaren type ion time-of-flight spectrometers taking into account also field penetration effects. The developed analytical formulae at various level of approximation are compared with ray tracing simulations and the effects are also illustrated on an experimental example.
Geometric meaning of high-order exceptional points in non-Hermitian Su–Schrieffer–Heeger model
Authors: Liu Tong , Li Jing-Quan , Zhang Zhi-Xu , Zhong Li-Nan , Cui Wen-Xue , Wang Hong-Fu
Published: January 2025

We investigate the geometric meaning of high-order exceptional points (EPs) in non-Hermitian Su–Schrieffer–Heeger model. High-order EPs are highly associated with the non-Bloch parity-time (

PT

) symmetry, a novel type of

PT

symmetry caused by the non-Hermitian skin effect (NHSE). The bulk states arising from the NHSE possess higher-order EPs at the critical point of the non-Bloch

PT

phase transition. We also analyze the phase transition using the ratio of complex eigenenergies and employ saddle point theory to further clarify the geometric significance of higher-order EPs and non-Bloch

PT

phase transition. Finally, we generally prove that in an extended two-band non-Hermitian system, the values of generalized Brillouin zone at high-order EPs are zero or infinity. This work helps us further understand high-order EPs in nonreciprocal topological systems.
Micromagnetic simulations of magnon–magnon coupling in synthetic antiferromagnets with tilted magnetic anisotropy
Authors: Chen Xing , Zheng Cuixiu , Xu Haoxiang , Liu Yaowen
Published: January 2025

Hybrid magnonics has attracted extensive attention for its potential applications in quantum information processing, especially following the discovery of strong coupling in magnon–magnon hybrid systems. In this paper, we studied the coupling phenomena between the left-handed (LH) and right-handed (RH) magnon modes in synthetic antiferromagnets with a tilted perpendicular magnetic anisotropy (PMA). By tilting the PMA at a certain angle from the film normal, we achieved strong magnon–magnon coupling without the need for an external magnetic field. The resulting hybrid eigenmodes exhibit characteristics of a linear combination of pure LH and RH modes. In addition, micromagnetic simulations revealed in detail the gradual change of hybrid resonance modes from approximately linear to elliptic, and eventually to circular polarization as the coupling strength gradually decreases. We also examined the effects of an applied magnetic field on the coupling strength and mechanism between the two eigenmodes. These findings provide valuable insights into magnetic dynamics within hybrid magnonic systems for spintronic applications involving magnon polarization.
Strain dependent properties of the Bi2Sr2CaCu2O8 superconductor: an ab initio study
Authors: Yelpo Carla , Favre Sofía , Ariosa Daniel , Faccio Ricardo
Published: January 2025

Ab initio calculations were performed to investigate the effects of strain on the structural, electronic, and vibrational properties of the Bi2Sr2CaCu2O8 (Bi-2212) compound. To accurately represent the Bi-2212 ground state, a modulation correction was applied, generating a distorted structure with lower symmetry that better represents the incommensurate superstructure observed in this compound. Phonon spectra and electronic properties were calculated under various levels of c-axis strain, ranging from −2.0% to +2.0%. For the electronic properties, minor changes were observed in the electronic density of states and band structure. However, trends could be identified by analyzing the fine features of the band structure through a tight-binding model. The most significant changes were observed in the vibrational properties, where different trends emerged for the various Raman-active modes. The changes observed in the vibrational and electronic properties can be explained by examining the distances and overlap populations of the relevant bonds, as well as the reduced mass of certain modes. This work can serve as an input for analyzing experimental measurements, helping to distinguish structural effects from others.
Influence of aqueous KMnO4 concentration on the structural and optical properties of reduced-graphene oxide nanosheets for enhanced electrical conductivity
Authors: Ali Sahar Mohammed , Hussein Emad Hameed , Dakhil Osama Abdul Azeez
Published: January 2025

It is reputed that potassium permanganate (KMnO4) powder is a very crucial material used as an oxidant for the preparation of reduced-graphene oxide (rGO) based on Hummer’s method. However, since the oxidant molarity is unknown when using the powder, a new work in which a solution-phased KMnO4 with different concentrations of 0.5 M, 1 M, and 1.5 M was introduced to change the structural, morphological, optical, and electrical properties of rGO. Characterization tools confirmed the formation of rGO nanosheets with different energy gaps depending on the concentrations. Hence, as Raman spectra demonstrated, the crystalline qualities of the nanosheets were highly influenced by the concentrations. The change in the morphological and structural properties of rGO led to a high increase the electric conductivity by lowering the oxidant molarity. In contrast, the maximum value of the dielectric constant was observed at the highest concentration. Moreover, a symmetrical tangent loss was observed in the frequencies less than 100 kHz at a molarity of 1 M. Therefore, 1 M oxidant was selected as the optimal concentration for high-conductivity, high-tangent loss rGO nanosheets. Thus, this modification could improve the rGO features, especially the electrical properties for future electronics.
Generalized spin helix states in quantum spin graphs
Authors: Zhang C H , Shi Y B , Song Z
Published: January 2025

In general, the summation of a set of sub-Hamiltonians cannot share a common eigenstate of each one, only if it is an unentangled product state, such as a spin helix state in quantum spin system. Here we present a method, referred to as the building block method (BBM), for constructing possible spin-1/2 XXZ Heisenberg lattice systems possessing spin helix states. We focus on two types of XXZ dimers as basic elements, with a non-Hermitian parity-time (

P
T

) magnetic field and Hermitian Dzyaloshinskii-Moriya interaction (DMI), which share the same degenerate eigenstates. Based on these two building blocks, one can construct a variety of Heisenberg quantum spin systems, which support helix states with zero energy. Furthermore, we show that such systems act as quantum spin graphs since they obey the analogs of Kirchhoff’s laws for sets of spin helix states when the non-Hermitian

P
T

terms cancel each other out. In addition, the dynamic response of the helix states for three types of perturbations is also investigated analytically and numerically. Our findings provide a way to study quantum spin systems on irregular lattices.
The Lunar Gravitational-wave Antenna: mission studies and science case
Authors: Ajith Parameswaran , Seoane Pau Amaro , Sedda Manuel Arca , Arcodia Riccardo , Badaracco Francesca , Banerjee Biswajit , Belgacem Enis , Benetti Giovanni , Benetti Stefano , Bobrick Alexey , Bonforte Alessandro , Bortolas Elisa , Braito Valentina , Branchesi Marica , Burrows Adam , Cappellaro Enrico , Ceca Roberto Della , Chakraborty Chandrachur , Subrahmanya Shreevathsa Chalathadka , Coughlin Michael W. , Covino Stefano , Derdzinski Andrea , Doshi Aayushi , Falanga Maurizio , Foffa Stefano , Franchini Alessia , Frigeri Alessandro , Futaana Yoshifumi , Gerberding Oliver , Gill Kiranjyot , Giovanni Matteo Di , Giudice Ines Francesca , Giustini Margherita , Gläser Philipp , Harms Jan , van Heijningen Joris , Iacovelli Francesco , Kavanagh Bradley J. , Kawamura Taichi , Kenath Arun , Keppler Elisabeth-Adelheid , Kobayashi Chiaki , Komatsu Goro , Korol Valeriya , Krishnendu N.V. , Kumar Prayush , Longo Francesco , Maggiore Michele , Mancarella Michele , Maselli Andrea , Mastrobuono-Battisti Alessandra , Mazzarini Francesco , Melandri Andrea , Melini Daniele , Menina Sabrina , Miniutti Giovanni , Mitra Deeshani , Morán-Fraile Javier , Mukherjee Suvodip , Muttoni Niccolò , Olivieri Marco , Onori Francesca , Papa Maria Alessandra , Patat Ferdinando , Perali Andrea , Piran Tsvi , Piranomonte Silvia , Pol Alberto Roper , Pookkillath Masroor C. , Prasad R. , Prasad Vaishak , Rosa Alessandra De , Chowdhury Sourav Roy , Serafinelli Roberto , Sesana Alberto , Severgnini Paola , Stallone Angela , Tissino Jacopo , Tkalčić Hrvoje , Tomasella Lina , Toscani Martina , Vartanyan David , Vignali Cristian , Zaccarelli Lucia , Zeoli Morgane , Zuccarello Luciano
Published: January 2025

The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response of the Moon to gravitational waves (GWs). Given the size of the Moon and the expected noise produced by the lunar seismic background, the LGWA would be able to observe GWs from about 1 mHz to 1 Hz. This would make the LGWA the missing link between space-borne detectors like LISA with peak sensitivities around a few millihertz and proposed future terrestrial detectors like Einstein Telescope or Cosmic Explorer. In this article, we provide a first comprehensive analysis of the LGWA science case including its multi-messenger aspects and lunar science with LGWA data. We also describe the scientific analyses of the Moon required to plan the LGWA mission.
Dust collapse and horizon formation in quadratic gravity
Authors: Buoninfante Luca , Filippo Francesco Di , Kolář Ivan , Saueressig Frank
Published: January 2025

Quadratic Gravity supplements the Einstein-Hilbert action by terms quadratic in the spacetime curvature. This leads to a rich phase space of static, compact gravitating objects including the Schwarzschild black hole, wormholes, and naked singularities. For the first time, we study the collapse of a spherically symmetric star with uniform dust density in this setting. We assume that the interior geometry respects the symmetries of the matter configuration, i.e., homogeneity and isotropy, thus it is insensitive to the Weyl-squared term and the interior dynamics is fully determined by R and R
2.
As our main result, we find that the collapse leads to the formation of a horizon, implying that the endpoint of a uniform dust collapse with a homogeneous and isotropic interior is not a horizonless spacetime. We also show that the curvature-squared contribution is responsible for making the collapse into a singularity faster than the standard Oppenheimer-Snyder scenario. Furthermore, the junction conditions connecting spacetime inside and outside the matter distribution are found to be significantly more constraining than their counterparts in General Relativity and we discuss key properties of any exterior solution matching to the spacetime inside the collapsing star. Finally, we comment on the potentially non-generic behavior entailed by our assumptions.
ITER NBI operational window and power availability constraints due to shine-through losses
Authors: Vincenzi P. , Schneider M. , Veltri P. , Artaud J.F. , Loarte A. , Nicolici S. , Poggi C. , Polevoi A.R. , Snicker A.
Published: January 2025

This paper explores the operational boundaries and power availability of the neutral beam injection (NBI) system in ITER, with a specific focus on shine-through (ST) loss prevention. ST, a phenomenon where part of the injected neutral beam remains un-ionized in the plasma and directly impacts the first wall components, poses a significant risk to the lifetime of ITER’s plasma-facing components (PFCs). The operational window for NBI is consequently constrained by these losses, which are influenced by factors such as plasma density, beam energy, and injection geometry. Leveraging advanced numerical simulations, we investigate these dependencies across various ITER plasma scenarios, particularly for the DT-1 phase, which will mark the first NBI operations. In light of recent ITER blanket design changes, our analysis refines previous estimates of the maximum acceptable ST power on PFCs. We then present a new heuristic formula which permits the calculation of the ST fraction and the minimum plasma density that permits ITER NBI operations as a function of global variables. This allows for establishing operational limits for Hydrogen and Deuterium NBI in Hydrogen, Deuterium, and Deuterium–Tritium plasmas. Additionally, we compare commonly used beam ionisation codes for ITER and tokamak simulations, evaluating their reliability in the investigated parameter space. The findings of this study are crucial for ensuring the efficient operation of the NBI system during ITER’s experimental phases. They define the conditions under which beam power can be fully utilised without compromising operational lifetime, thereby informing future plasma operation plans and contributing to the success of ITER’s scientific objectives.
Accuracy in evaluating convective heat transfer coefficient by RANS CFD simulations in a rectangular channel with high aspect ratio and V-shaped ribs
Authors: Corti M , Gramazio P , Fustinoni D , Niro A
Published: January 2025

In the framework of heat transfer enhancement inside channels with ribbed surfaces, V-shaped ribs are placed as the most promising among the standard-shaped ribs. This works aims to present a numerical analysis of heat transfer characteristics for forced convection inside a rectangular channel with high aspect ratio 1:10 equipped with V-shaped ribs. CFD simulations are carried out by means of Reynolds Averaged Navier-Stokes (RANS) equations, working with an air flow inside a narrow rectangular channel 120 mm wide and 840 mm long. V-shaped ribs have square cross section and they have been tested both with the tip of the V pointing downwards both upwards with respect to the channel inlet. For each configuration three different values of dimensionless pitch (10, 20 and 40) have been analysed. Comparisons between numerical and experimental data on convective global heat transfer coefficient and pressure drops are presented, showing very good agreement. Finding a properly working CFD model is useful for authors because this work, together with previous studies on 90° and 60° ribs, aims to be exploited during parametric early design-phases of new heat exchangers.
Computational fluid dynamics simulation of the homogeneous flow regime in a large-scale bubble column
Authors: Varallo N , Besagni G , Mereu R , Inzoli F
Published: January 2025

Bubble column reactors are widely used in various industrial applications, yet their characterisation at both global and local scales remains highly complex. This study presents a CFD Eulerian multi-fluid approach to model the hydrodynamics of large-scale bubble columns, focusing on the homogeneous flow regime. Transient 3D simulations were performed using the commercial software ANSYS Fluent 2023 R2, assuming a fixed mono- or poly-dispersed bubble size distribution to represent the dispersed gas phase. The results were thoroughly analysed and the discrepancies between the numerical results and the experimental data were discussed, highlighting areas for future improvement.
Evaporation of arrays of single-component drops on hydrophobic and hydrophilic surfaces
Authors: Tonini S , Cossali G E
Published: January 2025

The paper focuses on modelling the evaporation of arrays of single-component identical sessile droplets, a phenomenon encountered in various applications. An analytical approach is used and developed to treat ordered and scattered sessile drop arrays of any numerosity. An approximate analytical solution for the vapour field and evaporation fluxes from general arrays of sessile drops on any type of substrate (hydrophobic or hydrophilic) is found by a proper superposition of analytical solutions of single drop fields. Comparison with accurate numerical solutions and available experimental results validates the approach. An analysis of ordered and scattered square arrays from 4 to 49 drops on substrates with contact angles from 30° to 150°, is reported and used to study the dependence of the evaporation screening coefficients on array patterns.
Measurement of thermal diffusivity with a modified Angstrom method
Authors: Piva S
Published: January 2025

A methodology has been developed to measure the thermal diffusivity of high thermal conductivity solid materials. The basic idea traces back to the Ångström method, but the implementation differs in some points. Originally the specimen was free to the environment, here the specimen is thermally insulated to reduce, and control, the effects of natural convection. An appropriate analytical solution is used to calculate temperature distribution. The original two-point approach is replaced by a parameter estimation technique to consider multiple measurement points and reduce the final uncertainty. The methodology is used for a pure copper bar. The results are compared with the data available in the literature. The measured thermal diffusivity is 1.16±0.07·10−4 m2/s while the most reliable data available in the literature is 1.17±0.04·10−4 m2/s. The agreement of the present value with those available in the literature is excellent. This makes the use of this simple analytical approach attractive.
Energy transition audits in industries located in Valencian region
Authors: Cañada-Soriano Mar , Peñalvo-López Elisa , Montagud-Montalvá Carla , Valencia-Salazar Iván
Published: January 2025

The industrial sector is a major global consumer of energy, and meeting Europe’s climate neutrality targets will require a complete transformation of the global energy industry. To this end, Energy Transition Audits (ETAs) provide industries with a comprehensive and tailored action plans to reduce their energy consumption while mitigating the impact of CO2 emissions. In this context, this work presents the first results of an Energy Transition Audit conducted in a Valencian food processing facility within the framework of the European project EnTRAINER- Energy Transition Audits towards Decarbonisation. Starting from the industry baseline in terms of energy consumption and costs and production through a one-year analysis, five improvement actions are proposed and evaluated using the following performance indicators: energy and cost savings along with emissions reduction. Finally, the improvement measures are prioritized based on the company’s emissions reduction targets. Therefore, this innovative approach empowers the industries to monitor their progress towards achieving their decarbonization targets.
Numerical investigation on geometrical parameter effects of metal foams in liquid cooling efficiency of battery thermal management within phase change materials
Authors: Arumugam A , Buonomo B , Nardini S , Plomitallo R E , Manca O
Published: January 2025

The objective of this numerical study is to evaluate the effects of geometrical parameters of a metal foam inserted along with a chosen PCM material on the efficiency of liquid cooling of lithium polymer-based batteries. A three-dimensional model of a lithium manganese dioxide battery module is chosen for the analysis purpose. The analysis is performed by placing the module inside a parallelopiped based arrangement at the centre position, which is cooled by liquid flowing through the tubes by means of convection phenomenon. The tubes placed in the arrangement are assumed at a constant temperature and the entire module is adiabatic in nature. The governing physical equations involved in the analysis are based on the Local Thermal Non-Equilibrium constrains. The numerical model is solved using the finite volume technique using the Ansys-Fluent software. The study involves the analysis of thermal management for different pore density values of metal foam such as 5, 10, 20 and 40 with different C-rates of 0.5 and 1C respectively. The change in the internal resistance of the battery is determined using the Generalized Reduced Gradient technique. The analysis is interpreted by the temperature and liquid fraction profiles of the battery module.
Optimal design of thermal storage in hybrid energy systems: application to a laboratory-scale case study with experimental validation
Authors: Bianco N , Di Somma M , Graditi G , Mongibello L
Published: January 2025

The benefits of thermal storage in hybrid energy systems (HESs) are multiple, being among others the enhancement of flexibility of the network and of the efficiency in the energy resources use, by also reducing the overall cost of the energy system. Choosing the capacity of TSS to minimize the operational cost of the HES is not a trivial task, depending on several variables existing at both supply and demand sides. The contribution of this paper is to present the experimental validation of an innovative optimization model aiming to identify the optimal capacity of TSS in HESs that maximizes the economic performances. The optimization model is based on a mixed-integer linear programming approach and allows determining the optimal hourly operating strategies of the system components as well as the optimal capacity of the TSS, while minimizing the total daily energy costs. The optimized hourly operation schedule of the HES was simulated experimentally by using one of the systems from the TSS laboratory of ENEA Portici Research Center. The experimental results demonstrated the practical applicability of the proposed optimization model. In fact, a good overlap was found between the results obtained from the implementation of the optimization model with those obtained from the experimental simulation, both considering energy and economic data.
Preliminary assessment of a two-phase direct cooling of Lithium-Ion battery pack for e-bike mobility
Authors: Giammichele L , Colarossi D , Falone M , Fioretti F
Published: January 2025

Electric mobility is playing an increasingly central role in emission reduction policies to mitigate climate change effect. During the operation of electric vehicles, the batteries may be subject to high variation of the required current, which can lead to a sudden increase in the cell temperature. If this condition occurs repeatedly, there would be a reduction in battery capacity and useful life, and autonomy reduction of the electric vehicle. In the worst case, this problem can lead to the thermal runaway. Therefore, cooling of electric vehicle propulsion systems is a fundamental issue for the electric mobility development. In this article we propose an innovative cooling system using a dielectric low boiling fluid in which the batteries are directly immersed. The system was tested on an electric bicycle under real operative conditions. A special test bench was realized, consisting of a real electric bicycle, a training roller to simulate the load due to road slope and an external electric motor to simulate the pedaling of the cyclist. The results show a substantial decrease in the temperature of the cells with the proposed cooling system and there was a marked improvement in the temperature uniformity of the cells inside the battery pack.
Preliminary experimental studies on coalescer efficiency for liquid-liquid separation
Authors: Carraretto I M , Scapinello D , Bellini R , Colombo L P M , Molinaroli L , Manzolini G
Published: January 2025

The international organizations have identified both water demand and accessibility as critical challenges with both current and future implications for human well-being. In reason of that due to the growing demand, it is essential to advance the technologies used in freshwater production, focusing on sustainability while maintaining operational efficiency. Within the HORIZON 2020 program, it was thought to integrate the desalination processes with Renewable Energy Sources (RES). The desalination process is based on Forward Osmosis (FO), which uses a membrane to split pure water from seawater by exploiting the osmotic pressure difference between the feed solution (i.e., seawater) and the draw solution (i.e., permeate side). For the process to be effective, a low-cost method for regenerating the diluted draw solution is necessary. Hence, a viable alternative is to deploy a thermo-responsive polymeric draw agent that can be regenerated by the heat power rejected from a CO2 power cycle integrated with a Concentrated Solar Power. To perform the separation, a liquid-liquid separator (i.e., coalescer), mostly deployed in the oil and gas sector, is proposed to split the fresh-water from the polymeric draw solution. Hence, the aim of this work is to preliminarily assess the performances of the coalescer, aiming at the formulation of an experimental efficiency expression. Expression that is function of: (1) temperature at which the regeneration is performed, (2) residence time, and (3) draw concentration in the initial solution. The draw agent used in the experimental campaign is the PAGB2000, a thermo-responsive co-polymer that has a Lower Critical Solution Temperature (LCST) above which the fluid splits in two distinct phases: a polymer-rich (more concentrated), and a polymer-poor (more diluted). From the analysis it results that the coalescer performances strongly increase with both temperature and residence time, indeed efficiency achieves values near to 100%. On the other hand, the performances slightly worsen with increasing the initial draw concentration. Eventually, having an efficiency formulation can both help the design process of the desalination plant and provide an understanding on how much this technology can be applied in context far from the ones it was developed for.
Development of a numerical model of CaCl2 hydration and dehydration reaction for thermochemical energy storage
Authors: Baccega E , Zhang Y , Su Y , Bottarelli M
Published: January 2025

Periodical variations experienced by buildings’ energy demand and supply might be tackled by means of Thermal Energy Storage (TES) systems. Among these, thermochemical heat storage (TCHS) by means of thermochemical material (TCM) is one of the most promising, allowing the greatest energy storage density per unit volume, negligible heat losses and long-term storage. As part of the Horizon Europe project “ECHO”, a preliminary 2D model of the TCHS system was developed with the software COMSOL Multiphysics as a tool to support the real-scale prototype design, anticipating the behaviour of the system, as well as the implementation of the control algorithm. The model was implemented to work in both charge (dehydration) and discharge (hydration) without having to change the reaction kinetics equation from time to time, only based on the instant-by-instant boundary conditions. This ability to switch from hydration to dehydration and vice versa at any time makes it possible to estimate the performance of the TCM even in the event of not being completely hydrated or dehydrated, and also to establish some relationship between the TCM charging and discharging times.
Stability analysis of an anisotropic uniformly heated/cooled porous layer
Authors: Barletta A , Celli M , Brandão P V , Lazzari S , Ghedini E
Published: January 2025

The flow resulting from the combination of forced and natural convection within a horizontal porous layer filled with Newtonian fluid is analyzed. The layer boundaries are subjected to uniform and symmetrical heating/cooling. The porous layer is anisotropic such as the permeability is function of the coordinates, and a fully developed flow occurs in the layer, where the temperature is a function of both spanwise and streamwise directions. The latter steady basic state undergoes the onset of thermal instability for adequate values of the Darcy–Rayleigh number, with the neutral stability condition being heavily influenced by the Péclet number, which is linked to the mass flow rate of the basic state. A streamfunction approach is applied and the normal modes method is employed to investigate the linear stability of the basic state. The system of ordinary differential equations obtained is tackled numerically and the critical values of the governing parameters are studied as functions of the Péclet number and of the permeabilities fraction.
Topology optimization using variable-porosity metal foams: design of conduction paths for cooling a heat generating disc and comparison with tree-shaped architectures
Authors: Bianco N , Fragnito A , Iasiello M , Mauro G M
Published: January 2025

Topology optimization (TO) is a design algorithm providing the optimal material layout within a design domain to minimize/maximize an objective function. In thermal science, for instance, it can be used to optimize the design of heat sinks to minimize thermal compliance, entropy generation, average temperature, etc. Recently, classical TO frameworks have been enhanced in multi-material TO in order to include more materials, thereby enhancing the degrees of freedom of the system, and thus ensuring better thermal performance. This work implements both TO and multi-material TO (MMTO) to address a benchmark heat conduction problem, i.e., the cooling of a circular heat generating volume through heat conduction paths. The heat generation is uniform in the disc, the rim is adiabatic, while the centre is set at a fixed temperature – Dirichlet boundary condition – and serves as heat sink. In TO the choice is between void and high-conductivity material, while in MMTO variable-porosity metal foams are integrated. The interpolation of the materials’ thermal conductivity is conducted via an ordered solid isotropic material penalization (SIMP) algorithm. The distinction between materials is attained by setting different thresholds in the interpolation and projection functions. The dimensionless global thermal resistance and domain average temperature are alternately addressed as objective functions to be minimized at equal weight of the system. The findings unveil that MMTO outperforms TO, which outperforms constructal tree networks, considering in the latter case different configurations of different complexity.
Estimation of flow boiling heat transfer coefficient in enhanced tubes. Benchmark correlations and ANN approach
Authors: Passarelli A F , Mastrullo R , Revellin R , Viscito L , Mauro A W
Published: January 2025

This paper addresses the critical gap in predicting the heat transfer coefficient during flow boiling in enhanced tubes, where the use of conventional correlations and predictive methods developed for smooth surfaces do not usually provide satisfactory results. For such purpose, a comprehensive database was collected from existing literature, including a wide range of operating conditions and enhanced tube geometries from several independent sources. The dataset includes mass flow rates spanning from 50 to 1000 kg/m2s, vapor qualities from the onset of boiling (x=0.0) to the dry-out occurrence and beyond (x=0.99), reduced pressures from 0.05 to 0.80, and tube diameters (measured up to the fin tip) from 0.7 to 11.9 mm, for a total amount of approximately 3000 data points.

Existing flow boiling heat transfer coefficient predictive methods for enhanced tubes were implemented and tested with the present dataset, proving a limited accuracy for most of them mainly in case of testing beyond the specific parameter ranges they were developed for. Extrapolation frequently resulted in statistically poor or even non-physical outcomes. Several artificial neural network models were then developed, according to sensitivity analysis approach to look for potential input parameters and network structures. Specifically, two approaches were employed: a standard neural network model and a correlated informed neural network (CINN), integrating physical correlations into the network’s architecture, thus informing the model with physical principles that govern the heat transfer process. Despite a lower overall accuracy, the correlated informed neural network demonstrated superior reliability than standard one, resulting in an instrument to improve the accuracy of existing correlations.
Two-Phase Pressure Drops Analysis in a Chevron-Type Corrugated Channel Using Image Segmentation for Void Fraction Estimation
Authors: Passoni S , Ferrario A , Mereu R , Inzoli F
Published: January 2025

This study examines the pressure drops and flow patterns in a Chevron-type Compact Plate Heat Exchanger (CPHE) with air-water two-phase mixture under adiabatic conditions. A transparent replica channel, made from epoxy resin, was used to mimic the heat exchanger’s fluid dynamics and allow for optical access. The channel featured a 63° corrugation angle, 2.5 mm depth, and 8.9 mm pitch, yielding a global enlargement factor of 1.17. A particular inlet section was designed to ensure even phase mixing and distribution. Operating conditions varied from 6 to 365 kg/m2s for water and 0.02 to 5 kg/m2s for air, expanding the range of previous studies. High-framerate back-illuminated visualizations provided detailed observations of the flow patterns. Moreover, frame-by-frame void fraction was estimated via HSV video analysis adopting a convolutional neural network (U-Net) to produce binary masks and estimate gas bubble volumes and via a volume-reconstruction algorithm exploiting the pseudo-2D shape of the channel. A novel correlation for Darcy’s friction factor based on Reynolds number was developed for single-phase flow, complemented by an analysis of two-phase pressure drops using a two-phase multiplier correlated with the Lockhart-Martinelli parameter. The incorporation of void fraction data significantly improved their modelling accuracy.
Changes in the role of Pacific decadal oscillation on East Asian winter surface temperature
Authors: Lee Doo Young , Yeh Sang-Wook , Jeong Hyein , Park Hyo-Seok
Published: January 2025

The complex interaction between the Pacific decadal oscillation (PDO) and East Asian winter temperatures remains unclear. This study reveals that since the early 2000s, East Asia has experienced a strengthening of Aleutian low (AL) and Siberian high (SH) during negative PDO phases, leading to an intensified East Asian winter monsoon (EAWM). The increased pressure gradient between the SH and the AL, driven by warming in the western Pacific associated with the negative PDO phase, has significantly contributed to a shift toward cooling in East Asia (105°–150° E, 20°–50° N) since the early 2000s. Observations and model simulations provide evidence that the enhanced tropical convection in the western Pacific under a negative PDO phase has intensified the atmospheric circulations associated with the EAWM since the early 2000s. Understanding these dynamics is crucial for improving winter temperature forecasts in East Asia.
Volume changing symmetries by matrix product operators
Authors: Borsi Márton , Pozsgay Balázs
Published: January 2025

We consider spin chain models with exotic symmetries that change the length of the spin chain. It is known that the XXZ Heisenberg spin chain at the supersymmetric point

Δ
=
−
1

/

2

possesses such a symmetry: it is given by the supersymmetry generators, which change the length of the chain by one unit. We show that volume changing symmetries exist also in other spin chain models, and that they can be constructed using a special tensor network, which is a simple generalization of a Matrix Product Operator (MPO). As examples we consider the folded XXZ model and its perturbations, and also a new hopping model that is defined on constrained Hilbert spaces. We show that the volume changing symmetries are not related to integrability: the symmetries can survive even non-integrable perturbations. We also show that the known supersymmetry generator of the XXZ chain with

Δ
=
−
1

/

2

can also be expressed as a generalized MPO.
Drying Characteristics of Red Ginger Using Tray Dryer Integrated with Biomass Pyrolysis Reactor
Authors: Hasibuan Rosdanelli , Haryanto Bode , Nafsun Aainaa Izyan , Pramananda Viqry , Siregar Fatimah Fahira , Fazillah Risma
Published: January 2025

Red ginger is a rhizome plant that is often used as a complementary spice, a mixture in food and drinks, and as herbal medicine. One of the post-harvest processing of red ginger is drying. Drying aims to reduce the water content of the material to the point where the growth of microorganisms and destructive enzyme activity can be prevented. One of the drying tools that can be used in drying red ginger is a tray dryer. However, heating the drying air generally still uses fossil fuels as an energy source, so it can produce emissions that pollute the air. In addition, the availability of fossil energy is also limited, expensive, and will continue to increase. Therefore, the use of fossil fuels can be replaced with biomass which is a renewable and sustainable energy source. This study aims to examine the effect of tray height (20 cm, 40 cm, 60 cm) on the drying characteristics of red ginger using a tray dryer integrated with a biomass pyrolysis reactor as a source of hot air. The results showed that a low tray resulted in a shorter drying time, but the final water content was higher. The best tray position was obtained at a height of 60 cm, with a drying time of 290 min, a final water content of 9.711%, and the highest drying rate of 61.10 g/m2.min.
Forward modelling of a fault using self-potential method
Authors: Aufia Yasrifa Fitri , Mahardika Harry
Published: January 2025

This study aims to enhance the interpretation of subsurface features through the self-potential method, a geophysical approach that provides insight into geological processes essential for effective fault detection. Although prior studies emphasize quantitative self-potential analyses, there is limited qualitative modelling to simulate realistic fault responses. This study employs forward modelling analysis using synthetic data to evaluate subsurface model responses close to field data. By modelling three simple anomaly forms: sphere, cylinder, and plate, it has been observed that parameter variations affect the resulting self-potential anomaly response. Results indicate that increasing polarization angles and dipole moments enhance self-potential responses across models, while depth variations show an inverse relationship, with shallower sources producing stronger signals. The modelling results can be used as a reference to validate field data interpretation, where high anomaly values correlate with extended, deeper faults or high-permeability zones.