bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-meron interactions and statistics in two-dimensional materials
Authors: Lu Xiaobo , Zhu Linghan , Yang Li
Published: April 2022

As a fundamental type of topological spin textures in two-dimensional (2D) magnets, a magnetic meron carries half-integer topological charge and forms a pair with its antithesis to keep the stability in materials. However, it is challenging to quantitatively calculate merons and their dynamics by using the widely used continuum model because of the characteristic highly inhomogeneous spin textures. In this work, we develop a discrete method to address the concentrated spin structures around the core of merons. We reveal a logarithmic-scale interaction between merons when their distance is larger than twice their core size and obtain subsequent statistics of meron gas. The model also predicts how these properties of single and paired merons evolve with magnetic exchange interactions, and the results are in excellent agreement with the Monte Carlo simulations using the parameters of real 2D van der Waals magnetic materials. This discrete approach not only shows equilibrium static statistics of meron systems but also is useful to further explore the dynamic properties of merons through the quantified pairing interactions.
Pseudospin-one particles in the time-periodic dice lattice: a new approach to transport control
Authors: Majari Parisa
Published: April 2022

The controlling of the transmission in the pseudospin-one Dirac–Weyl systems offers a rich tool to study new concepts of massive Dirac electron tunneling by means of a time-dependent potential. The time-periodic potential is one of the experimental techniques to have more control over the tunneling effect. In this paper, we study the transmission coefficient for different sidebands to obtain total transmission. We show how the super Klein tunneling under special conditions is independent of the incidence angle, oscillation amplitude, frequency, and barrier width. We consider a band gap opening with different locations of the flat band and modulate the resonances by tuning free parameters in our system.
Transition from surface phonon-polariton to surface phonon–plasmon-polariton by thermal injection of free carriers
Authors: El-Helou Y , Wu K-T , Bruyant A , Woon W-Y , Kazan M
Published: April 2022

Surface phonon-polariton, surface plasmon-polariton, and surface phonon–plasmon-polariton are evanescent electromagnetic waves confined to the surfaces of different classes of materials, which gives each of them particular characteristics suitable for diverse applications. Natural or forced injection of free carriers in a dielectric may change the surface phonon-polariton into a surface phonon–plasmon-polariton. Understanding this effect provides an insight into the fundamental physics of surface electromagnetic waves on dielectrics and offers tools that can be used to develop new technologies. In this contribution, we experimentally study the transition from surface phonon-polariton to surface phonon–plasmon-polariton on a yttrium-doped aluminum nitride polycrystalline substrate by thermal injection of free carriers. We perform this study using reflectivity measurements in the far- and mid-infrared spectral range and at a variable temperature, taking the necessary precautions to eliminate any errors that may arise from measurement artifacts and inaccurate analysis of the spectra. We demonstrate that thermal injection of a significant free carrier density can tune the surface phonon-polariton into a much shorter mean free path surface phonon–plasmon-polariton.
Analytical theory for the crossover from retarded to non-retarded interactions between metal plates
Authors: Luengo-Márquez Juan , MacDowell Luis G
Published: April 2022

The van der Waals force established between two surfaces plays a central role in many phenomena, such as adhesion or friction. However, the dependence of this forces on the distance of separation between plates is very complex. Two widely different non-retarded and retarded regimes are well known, but these have been traditionally studied separately. Much less is known about the important experimentally accessible cross-over regime. In this study, we provide analytical approximations for the van der Waals forces between two plates that interpolates exactly between the short distance and long distance behavior, and provides new insight into the crossover from London to Casimir forces at finite temperature. At short distance, where the behavior is dominated by non-retarded interactions, we work out a very accurate simplified approximation for the Hamaker constant which adopts analytical form for both the Drude and Lorentz models of dielectric response. We apply our analytical expressions for the study of forces between metallic plates, and observe very good agreement with exact results from numerical calculations. Our results show that contributions of interband transitions remain important in the experimentally accessible regime of decades nm for several metals, including gold.
GNSS spoofing detection technology based on Doppler frequency shift difference correlation
Authors: Li Junzhi , Zhu Xiangwei , Ouyang Mingjun , Shen Dan , Chen Zhengkun , Dai Zhiqiang
Published: April 2022

Global navigation satellite system (GNSS) spoofing interference poses a great threat to the security of end users. Based on the same propagation path characteristics of the spoofing signals transmitted by a single antenna spoofing device, this paper proposes a method against single antenna spoofing jamming utilizing the Fréchet distance of Doppler frequency difference. When the receiver moves, the Doppler data in a window are fitted via the leastsquares method, and the Fréchet distance between the two satellite signals is calculated to obtain the similarity evaluation value between them. The detection of spoofing signal is carried out based on the evaluation value. We use real data to verify the detection performance of the method, and the experimental results show that the method can effectively distinguish the spoofing signal from the authentic signal. In addition, the method has low computational complexity and requires less additional information, which makes it possible to apply it in the anti-spoofing module of a GNSS receiver.
Effect of cobalt doping on the enhanced energy storage performance of 2D vanadium diselenide: experimental and theoretical investigations
Authors: K A Sree Raj , Adhikari Surajit , Radhakrishnan Sithara , Johari Priya , Rout Chandra Sekhar
Published: April 2022

Vanadium Diselenide (VSe2) is a prominent candidate in the 2D transition metal dichalcogenides family for energy storage applications. Herein, we report the experimental and theoretical investigations on the effect of cobalt doping in 1T-VSe2. The energy storage performance in terms of specific capacitance, stability and energy and power density is studied. It is observed that 3% Co doped VSe2 exhibits better energy storage performance as compared to other concentrations, with a specific capacitance of ∼193 F g−1 in a two-electrode symmetric configuration. First-principles Density Functional Theory based simulations support the experimental findings by suggesting an enhanced quantum capacitance value after the Co doping in the 1T-VSe2. By making use of the advantages of the specific electrode materials, a solid state asymmetric supercapacitor (SASC) is also assembled with MoS2 as the negative electrode. The assembled Co-VSe2//MoS2 SASC device shows excellent energy storage performance with a maximum energy density of 33.36 Wh kg−1 and a maximum power density of 5148 W kg−1 with a cyclic stability of 90% after 5000 galvano static charge discharge cycles.
Human blood biocompatibility and immunogenicity of scFvD2B PEGylated gold nanoparticles
Authors: Mitri Nadim , Rahme Kamil , Fracasso Giulio , Ghanem Esther
Published: April 2022

Single chain variable D2B antibody fragments (scFvD2Bs) exhibit high affinity binding to prostate specific membrane antigens overexpressed in metastatic prostate cancer (PC). Conjugation of scFvD2B to gold nanoparticles (AuNPs) would enhance its stability and plasma half-life circulation to shuttle theranostic agents in PC. In this study, we synthesized PEGylated scFvD2B-AuNPs (AuNPs-scFvD2B-PEG) and tested their integrity, biocompatibility, and immunogenicity in freshly withdrawn human blood. Prior to blood incubation, Zeta potential measurements, UV–Vis spectroscopy, and dynamic light scattering (DLS) were used to assess the physicochemical properties of our nano-complexes in the presence or absence of PEGylation. A surface plasmon resonance band shift of 2 and 4 nm confirmed the successful coating for AuNPs-scFvD2B and AuNPs-scFvD2B-PEG, respectively. Likewise, DLS revealed a size increase of ∼3 nm for AuNPs-scFvD2B and ∼19 nm for AuNPs-scFvD2B-PEG. Zeta potential increased from −34 to −19 mV for AuNPs-scFvD2B and reached −3 mV upon PEGylation. Similar assessment measures were applied post-incubation in human blood with additional immunogenicity tests, such as hemolysis assay, neutrophil function test, and pyridine formazan extraction. Interestingly, grafting PEG chains on AuNPs-scFvD2B precluded the binding of blood plasma proteins and reduced neutrophil activation level compared with naked AuNPs-citrate counterparts. Most likely, a hydrated negative PEG cloud shielded the NPs rendering blood compatiblility with less than 10% hemolysis. In conclusion, the biocompatible AuNPs-scFvD2B-PEG presents promising characteristics for PC targeted therapy, with minimal protein adsorption affinity, low immunorecognition, and reduced hemolytic activity.
Improving the photovoltaic properties of GaAs/GaAsBi pin diodes by inserting a compositionally graded layer at the hetero-interface
Authors: Kawata Hiromu , Hasegawa Sho , Nishinaka Hiroyuki , Yoshimoto Masahiro
Published: April 2022

We investigated the effect of inserting a compositionally graded layer at the GaAsBi/GaAs interface on the photovoltaic and light-emission properties of GaAs/GaAsBi pin diodes. When the pin diode is operated as a solar cell, inserting a graded layer improves the open-circuit bandgap–voltage offset (W
oc) to 0.51 V. This is comparable to or better than other materials—such as GaInNAs(Sb), which has a bandgap of 1.0 eV—that are expected to be used in multijunction solar cells. In contrast, W
oc can be as large as 0.71 V for a pin diode without a graded layer. When it is operated as a light-emitting diode, inserting a graded layer in such a diode suppresses nonradiative recombination by a factor of 1/50 based on its electroluminescence intensity. Inserting a graded layer also makes it possible to avoid deterioration of the peculiar hetero-interface where the transition from the non-metallic nature of GaAs to the metallic nature of GaAsBi occurs. Moreover, the graded layer is effective in avoiding a pile-up of oxygen at the interface at low temperatures when growth is interrupted just before growing the GaAsBi layer. Thus, inserting a graded layer is the key to improving the performance of minority-carrier devices containing GaAsBi.
Real-time fuzzy-pid synchronization of memristor-based chaotic circuit using graphical coded algorithm in secure communication applications
Authors: Guler Hasan
Published: April 2022

The main goal of this study is to implement real-time synchronization of a memristor-based chaotic circuit for secure communication on LabVIEW virtual instrument environments. Memristors can be used in chaotic circuits because of their nonlinear behavior. In this paper, an application for secure communication systems is proposed by using the chaotic property of the memristor. Phase portraits, Lyapunov exponential spectrum, and bifurcation diagrams of the memristor-based chaotic circuit were investigated. A Fuzzy-PID controller was used for master-slave synchronization of memristive chaotic circuit and in secure communication application, three images were also used for encryption and decryption. NI 6251 DAQ card was used to obtain real-time results. Information entropy values, correlation coefficients (CC), peak signal to noise ratio (PSNR), structural similarity index (SSIM), correlation coefficients for the horizontal, vertical and diagonal directions from the three encrypted images, number of pixels change rate (NPCR) and unified average changing intensity (UACI) are calculated to test encryption/decryption performance in the designed system. The results obtained from real-time applications and simulations prove that memristor-based chaotic circuits can be used in secure communication systems where privacy is important.
The ϕ meson production from small to large systems of ion collisions at

sNN=200

and 193 GeV
Authors: Mitrankov Iu M , Berdnikov Ya A , Berdnikov A Ya , Kotov D O , Mitrankova M M , Novitzky N
Published: April 2022

The measurement of ϕ meson production is a unique tool to explore the characteristics of the quark-gluon plasma. The ϕ meson has a small interaction cross section therefore its yields and elliptic flow are good probes of the quark-gluon plasma properties. The ϕ meson production can be sensitive to the strangeness enhancement effect and can provide information about the flavor dependence of energy loss and elliptic flow. Measurements in different nucleus-nucleus collisions allow us to perform a systematic investigation of the nuclear matter effects, system size and geometry influence on ϕ meson production. The PHENIX experiment has measured transverse momentum spectra, nuclear modification factors R

AB
, and elliptic anisotropy parameter v
2 for ϕ mesons in p+Al, p/d/3 He/Cu+Au collisions at

s

NN

=
200

GeV

and in U + U collisions at

s

NN

=
193

GeV

at midrapidity (∣η∣ < 0.35). The obtained results exhibit scaling of v
2 for ϕ mesons with eccentricity of participant nucleons (collision geometry), whereas the ϕ R

AB
values depend on the number of binary nucleon-nucleon collisions (system size). The comparison of experimental data on the ϕ meson to various model calculations (AMPT, iEBE-VISHNU and PYTHIA/Angantyr) suggests the importance of viscous hydrodynamics and the coalescence mechanism in describing the properties and hadronization of the QGP.
Comprehensive investigations on radiation shielding efficacy of bulk and nano Pb-Sn-Cd-Zn alloys
Authors: Kaur Taranjot , Vermani Yogesh K , Al-Buriahi M S , Alzahrani Jamila S , Singh Tejbir
Published: April 2022

The alloys with composition:

P

b

60

S

n

20

C

d

x

Z

n

20
−
x

,

where

x
=
0
,
5
,
10
,
15

and

20

mol
.
%

were fabricated at nano-scale as well as bulk scale using the convention melt quench technique. Different characterization techniques such as Transmission Electron Microscopy (TEM), Field Emission-Scanning Electron Microscopy (FE-SEM) and Energy Dispersive Spectroscopy (EDS) analysis were performed to verify the particle size reduction to nano-scale, surface morphology and elemental composition of Pb60Sn20CdxZn(20-x) alloy systems. These nano-structured and bulk alloy systems were experimentally investigated and compared for their potential use in the radiation shielding applications. Further, radiation shielding effectiveness against electron beam, proton beam, alpha and heavy carbon ion beams has also been investigated for fabricated bulk alloys using Geant4 simulations. Present theoretical and experimental analysis affirmed that the radiation shielding efficacy gets enhanced for ball-milled PbSnCdZn nano alloy specimens as compared to bulk counterparts.
Effects of Nb concentration on Nb-doped anatase TiO2: DFT + U calculations
Authors: Xiao Xiangjiang , Wang Jinfu , Zhu Hanming , Liu Lei , Liu Zuming , Tu Jielei
Published: April 2022

The crystal structure, formation energy, electronic structure, electrical properties and optical properties of anatase TiO2 with various Nb concentrations were studied by first-principles calculations based on density functional theory (DFT) and the Hubbard U correction. Firstly, the crystal structures of TiO2 with various Nb concentrations were optimized successfully. The higher concentrations of Nb facilitate the synthesis of Nb-doped TiO2 systems in an O-rich environment. Furthermore, the band structures and density of states prove that the electronic structure of Nb-doped TiO2 is mainly transformed by the hybridization of Ti 3d, Nb 4d and O 2p states. Next, broadening of the valence band and occupied states at the bottom of the conduction band enhance the conductivity of Nb-doped TiO2, and the conductivity reaches the maximum value at the high Nb-doping concentration of 6.25 at.%. Last but not least, the calculated optical properties show that the absorption edge of Nb-doped TiO2 produces an blue shift. TiO2 with Nb-doping concentration below 14.58 at.% exhibits the high transmittance in the visible region.
Errata and Addendum: Magnetic properties of an antiferromagnetic spin-1/2 XYZ model in the presence of different magnetic fields: finite-size effects of inhomogeneity property (2019, Commun. Theor. Phys.
71 1253–1260)
Authors: Kumar Sachin , Yusuf S M
Published: April 2022

We report the correct results for the antiferromagnetic s = 1/2 XYZ model system considered in (2019, Commun. Theor. Phys.
71 1253). We also point out the correct model system used for the reported results therein.
Measurement of muon-induced neutron yield at the China Jinping Underground Laboratory *
Authors: Zhao Lin , Luo Wentai , Bathe-Peters Lars , Chen Shaomin , Chouaki Mourad , Dou Wei , Guo Lei , Guo Ziyi , Hussain Ghulam , Li Jinjing , Liang Ye , Liu Qian , Luo Guang , Qi Ming , Shao Wenhui , Tang Jian , Wan Linyan , Wang Zhe , Wu Yiyang , Xu Benda , Xu Tong , Xu Weiran , Yang Yuzi , Yeh Minfang , Zhang Aiqiang , Zhang Bin
Published: April 2022

Solar, terrestrial, and supernova neutrino experiments are subject to muon-induced radioactive background. The China Jinping Underground Laboratory (CJPL), with its unique advantage of a 2400 m rock coverage and long distance from nuclear power plants, is ideal for MeV-scale neutrino experiments. Using a 1-ton prototype detector of the Jinping Neutrino Experiment (JNE), we detected 343 high-energy cosmic-ray muons and (7.86

3.97) muon-induced neutrons from an 820.28-day dataset at the first phase of CJPL (CJPL-I). Based on the muon-induced neutrons, we measured the corresponding muon-induced neutron yield in a liquid scintillator to be

μ−1g−1cm2 at an average muon energy of 340 GeV. We provided the first study for such neutron background at CJPL. A global fit including this measurement shows a power-law coefficient of (0.75

0.02) for the dependence of the neutron yield at the liquid scintillator on muon energy.
A New Fiber Detection Method for LAMOST Based on the Front-illuminated Method
Authors: Zhou Ming , Zhang Yong , Lv Guanru , Li Jian , Zhou Zengxiang , Liu Zhigang , Wang Jianping , Bai Zhongrui , Tian Yuan , Wang Mengxin , Wang Shuqing , Hu Hongzhuan , Zhai Chao , Chu Jiaru , Han Zhijie , Liu Mingxu , Dong Yiqiao , Yuan Hailong , Zhao Yongheng , Chu Yaoquan , Zhang Haotong
Published: April 2022

The double revolving fiber positioning technology is one of the key technologies for the success of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The accuracy of fiber positioning will directly affect the observation efficiency of LAMOST. To achieve higher fiber positioning accuracy, the original open-loop controlled fiber positioning system urgently needs to be upgraded into a closed-loop control system. The fiber detection is the most important part of the closed-loop controlled fiber positioning system. The back-illuminated detection method is usually used to detect the fiber position by directly detecting the light spot generated at the fiber end in the multi-fiber spectral surveys. In this paper, we introduce a new method to measure the fiber position based on the image of the front-illuminated LAMOST focal plane. The front-illuminated image does not require lighting devices inside the spectrograph, and it could reduce the instability and light pollution in the spectrograph end. Our method measures the fiber position by fitting the profile of the fiber pinhole with a 2D Gaussian function. A series of tests show that the relative position measurement precision of the front-illuminated method is about 0.″12, and the method could have the same accuracy as the back-illuminated method once the system bias is calibrated by a simple radial correction function. The required fiber positioning accuracy of LAMOST is 0.″4, and the new method satisfies the requirement of LAMOST fiber detection accuracy and could be used in the closed-loop fiber control system.
ARES: a fast and accurate tool for the identification of plasma stationary points and separatrix
Authors: Bonotto M. , Bettini P.
Published: April 2022

In this work, triangular C
1 interpolation based on Argyris element (AE) is used to develop the ARgyris element based searching (ARES) algorithm, an efficient tool for the accurate identification of stationary points (SPs), e.g. X-point, magnetic axis, snowflake point, etc and separatrix in magnetic confinement fusion application. AE-based interpolation allows the formulation of the nonlinear problem of SP identification on the triangle as a vectorial root-finding problem, addressed via different Newton-like algorithms. The proposed method is able to detect both first-order SP (e.g. X-points and magnetic axis, where the norm of the gradient vanishes) and second-order SP (e.g. snowflake points, where both the norm of the gradient and of the second derivatives vanishes). The separatrix is detected inside the triangles via the novel zero line searching algorithm, and is described by means of quintic spline interpolant of its components. Thanks to its modularity and efficiency, ARES is suitable to run on structured and unstructured triangular meshes, and can be readily integrated with any kind of Grad–Shafranov solver based on 2D triangular finite element method, or used for real-time SP and separatrix identification for control oriented purposes.
Coupling among neoclassical tearing modes, edge localized modes and Alfvén eigenmodes in HL-2A high
β
H-mode plasmas
Authors: Jiang M. , Xu Y. , Chen W. , Zhong W.L. , Shi P.W. , Shi Z.B. , Ding X.T. , Ke R. , Liu H.F. , Zhu Y.R. , Zou Y.P. , Li Z.J. , Wang T.B. , Zhang Y.P. , Yu L.M. , Yang Z.C. , Liu L.Z. , Wu N. , Ji X.Q. , Liu Yi , Xu M. , HL-2A Team
Published: April 2022

In this work, the coupling among several MHD modes across different spatial regions, including the neoclassical tearing mode (NTM) and two branches of Alfvén eigenmode (AE) in the core and the edge localized mode (ELM), has been investigated in the HL-2A high beta H-mode plasmas. The NTMs induce a saturated m/n = 1/1 helical core (m and n are the poloidal and toroidal mode numbers, respectively) through the ‘magnetic-flux pumping’ effect. The ELM crash results in a rapid (<1 ms) decrease of the NTM island width followed by a much slower recovery. The degree of the island-width drop is proportional to the normalized beta as well as the ELM size, and can be up to 60%. In addition, two branches of AEs, in the toroidal Alfvén eigenmode (TAE) and beta-induced Alfvén eigenmode (BAE) bands, become evident after the 2/1 NTM onset and their magnitudes are modulated by the 2/1 NTM rotation. Besides, the changes of the TAE and BAE amplitudes are closely related to the temporal evolution of the ELM crash event, implying the strong interaction between AEs and the ELM. It is found that the coupling among these MHD modes in the core region during the NTM phase regulates the edge transport, i.e., relaxation of the pressure profile, mitigation of the peeling-ballooning instability, reduction of the radial electric field shear and enhancement of the turbulent transport in the pedestal region.
RTS noise in semiconductor devices: time constants estimates and observation window analysis
Authors: da Silva Roberto , Wirth Gilson
Published: April 2022

We obtained a semi-analytical treatment considering estimators for the variance and variance of variance for the RTS noise as a function of the time observation. Our method also suggests a way to experimentally determine the constants of capture and emission in the case of a dominant trap and universal behaviors for the superposition from many traps. We present detailed closed-form expressions corroborated by MC simulations. We are sure to have an important tool to guide developers in building and analyzing low-frequency noise in semiconductor devices.
On the modelling of tritium transport phenomena at fluid-structure interfaces
Authors: Castrovinci F. M. , Bongiovì G. , Chiovaro P. , Di Maio P. A. , Franza F. , Quartararo A. , Spagnuolo G. A. , Vallone E.
Published: April 2022

One of the main functions of the DEMO Breeding Blanket (BB) system is to ensure the tritium breeding inside the reactor. Tritium is a beta emitter radioactive isotope, subjected to several processes that determine its permeation across materials and its leakage towards the environment, posing potential safety issues in terms of radiological hazard. Thus, the evaluation of tritium inventories inside components and tritium losses towards the environment plays a key role in the fulfilment of the pertinent BB safety requirements. In this regard, a research activity has been carried out, in close cooperation between the University of Palermo and the Karlsruhe Institute of Technology, focussing on the development of a multiphysical model that might realistically simulate 3D tritium transport phenomena across complex fluid-structure interfaces. Models, source terms and boundary conditions assumed for the analyses are herewith reported and critically discussed, together with the main results obtained.
Coupled Geothermal Energy Simulations
Authors: Meglio Armando Di , Massarotti Nicola , Mauro Alessandro , Trombetta Vincenzo
Published: April 2022

This paper presents the numerical solution of thermal field of a set of geothermal coaxial probes coupled with the surrounding soil. These probes, used for the excavation of Naples underground’s tunnels with the artificial ground freezing technique, are converted for the heat transfer fluid transport for a geothermal plant. One-dimensional energy equation has been used with a single unknown in order to extract the solution of the temperature inside the probe, the temperature of the fluid, which is a boundary condition for calculating the temperature range of the soil surrounding the probes. In turn, the latter is used as a source term for the solution of the energy equation for the fluid. This paper also presents a comparison between two different probe materials i) internal and external stainless-steel crown; ii) internal rigid PVC crown and external stainless-steel crown. Such a numerical scheme allows to take into account the 3D effects of the fluid dynamics in porous media as is the soil, and, at the same time, considering a “reduced order model” inside the geothermal probes, as is the 1D model, for considering the thermal coupling effects.
Assessment of operating temperature within the new pavilion for slag management in Terni
Authors: Manni Mattia , Fabiani Claudia , Nicolini Andrea , Pisello Anna Laura , Rossi Federico , Cotana Franco
Published: April 2022

The whole metallurgic sector produces up to 200 million tons of slag, which are tapped from the blast furnace (at a temperature of 1,500°C), and then need to be cooled down before disposal. These cooling processes are generally conducted open-air, significantly affecting local environmental quality of the surroundings. The present study aims at investigating the potential of an innovative slag cooling system housed within a pavilion, designed in order to minimize the emission of dust and pollutants out from the metallurgic plant. Such a system consists of a depressurized environment whose top surface is treated with black pigments and cooled down by water streams above it. Air is continuously extracted and then adequately filtered before being released outdoor. A numerical model was elaborated for evaluating the main heat flows developed within and through the pavilion’s envelope for the case study in Terni, central Italy. Once the physical and geometrical properties of the slag and the pavilion were defined, the heat exchanged with the air and water due to convection, as well as the latent heat dissipated through water evaporation was quantified. Results demonstrated the effectiveness of the water-based cooling system in keeping the roof temperature lower than 328 K without compromising the mechanical properties of the material. The evaporated water mass ranged between 4.2 kg h−1 and79.6 kg h−1 and was strongly influenced by seasonal weather conditions.
Numerical Investigation On Thermal Behaviours Of Latent Thermal Energy Storages With Pcm Partially Filled With Aluminum Foam
Authors: Buonomo Bernardo , Manca Oronzio , Nardini Sergio , Plomitallo Renato Elpidio
Published: April 2022

In this paper a numerical investigation on the effects of the metal foam into the Latent Heat Thermal Energy Storage System, based on a phase change material, is accomplished. The geometry of the system is a vertical shell and tube LHTESS made with two concentric aluminum tubes. The internal surface of the hollow cylinder is assumed at a constant temperature above the melting temperature of the PCM to simulate the heat transfer from a hot fluid. The other external surfaces are assumed adiabatic. The PCM is completely embedded in the volume between the two coaxial cylinders, it is pure paraffin wax with a low value of thermal conductivity and it melts in a range of temperatures. The metal foam is made of aluminum and it partially fills the volume starting from the internal cylinder with a thickness lower the differences between the external cylinder radius and internal one. The enthalpy-porosity theory is employed to simulate the phase change of the PCM and the metal foam is modelled as a porous media that follow the Brinkman-extended Darcy model. The governing equations are solved employing the Ansys-Fluent code. The results are shown in term of melting time, temperature and energy at varying of time and at varying the filling ratio.
Urban-Scale Energy Models: the relationship between cooling energy demand and urban form
Authors: Mutani G , Todeschi V , Santantonio S
Published: April 2022

To enhance the quality of life in cities, it is necessary to improve the energy performance of buildings together with a sustainable urban planning especially in high-density contexts. Previous works investigated the building shape, the urban morphology, and the local climate conditions to optimize the energy performance for space heating of buildings. The aim of this study is to validate a GIS-based engineering model to simulate the hourly energy demand for space cooling in residential buildings at neighborhood scale and to assess the relationship between the urban form and the energy performance in terms of cooling energy demand. A place- based methodology was applied to six neighborhoods in the city of Turin (Italy), identified as homogeneous zones with different building characteristics and urban contexts. The hourly cooling demand of residential buildings was studied starting from the energy balance at building scale, and then was applied at block of buildings scale with the support of GIS. This model was validated with a comparison of the results using CitySim tool and ISO 52016 assessment. In order to investigate the relationship between cooling energy demand and urban form, the GIS- based engineering model was applied to five typical blocks of buildings with different construction periods. The results show how cooling energy demand varies according to building characteristics and urban morphology in a continental-temperate climate. By this analysis, it is possible to identify the optimal block of building shape in Turin ensuring lower energy consumptions during the cooling season with different types of buildings.
Optimisation strategies for solar assisted heat pumps coupled to traditional thermal fields
Authors: Tagliafico L.A. , Cavalletti A. , Marafioti C. , Marchitto A.
Published: April 2022

The advantages of the solar assisted heat pumps are well-known but their diffusion on the market is still very limited. One of the main causes is associated to their complexity and almost always working under transient regime which can lead to frequent blocks especially when a low level of control and automatization is present. From the point of view of conceptual design, solar assisted heat pumps tend to be more subjected to blocks due to their serial asset. The present work illustrates the case study of the solar assisted heat pump pilot plant at Palacus, Genoa, equipped with a heat pump bypass which can directly connect the solar thermal field to either the domestic hot water or the space heating systems when the temperature in the circuit exceeds a fixed set point. This configuration allows therefore the use of the solar field either independently from the heat pump or interfaced with it, according to the external conditions. A numerical model within TRNSYS environment has been developed basing on the information collected on the pilot plant by the data acquisition system. A simulation of the working of the pilot plant along a typical year has been performed, evaluating its increased performance and optimisation thanks to the bypass.
Analytical and numerical modelling of biomass gasification in downdraft gasifiers
Authors: Moretti L , Arpino F. , Cortellessa G. , Dell’Isola M. , Ficco G , Grossi G. , Zuena F. , Di Palma M. , Vanoli L.
Published: April 2022

The ever-growing energy demand and environmental pollution level have pushed research interest toward the development of new promising technologies to utilize bioenergy sustainably. In this scenario, biomass gasification has been regarded as a promising renewable energy resource that, if efficiently exploited, can contribute to the reduction of dependency on fossil fuel and CO2 emissions from the power sector. Nevertheless, exploitation of biomass gasification still requires to overcome technological and logistical issues. In this work, the authors propose a general thermodynamic model able to predict the steady operating conditions of biomass gasification. Assuming thermodynamic equilibrium, the model is able to predict temperature, mass flow rate and composition of produced syngas. Moreover, a numerical model of the biomass gasification system has been developed by using the commercial software Aspen Plus. It is a steady-state zero-dimensional equilibrium model, based on the mass and energy balances, assuming the Gibbs free energy minimization. Aspen Plus allows building models of customized operative units using the Fortran code. In order to assure the performance of both analytical and Aspen Plus models, numerical results are compared with experimental data available in the scientific literature for downdraft gasifiers.
Computational Model For The Estimation Of Thermo-Energetic Properties In Dynamic Regime Of Existing Building Components
Authors: Mastino Costantino Carlo , Ricciu Roberto , Baccoli Roberto , Salaris Chiara , Innamoratii Roberto , Frattolilloi Andrea , Pacitto Antonio
Published: April 2022

The guidelines of the European community towards a low-carbon economic society identify one of the most important scenarios in the energy efficiency of existing buildings. The discrepancy between the requirement and availability of free heat (endogenous heat, solar radiation) in certain hours of the day and operating conditions, makes the steady-state hypothesis generally inappropriate. In particular, the oscillating component of the transmitted flow, compared to the average temperature difference, is regressive in winter and dominant in summer. From this it follows the reliability of the stationary forecast models in winter and the need for dynamic forecast models in summer. The dominance of the continental climate in the EU, compared to the Mediterranean one, led to the actual delay in the development of dynamic models, especially at a regulatory level. In this paper, a methodology for assessing the dynamic properties of a building component is evaluated. The methodology, based on heat transmission equations implements a numerical model for existing building components whose input data can be obtained from experimental measurements. The developed model has been used to estimate the energetic and thermal behaviour of a building envelope subjected to energy efficiency measures.
Comparison of heat transfer processes during selective and while body Newborn’s therapeutic hypotermia – case report
Authors: D. Bandoła , Z. Ostrowski , M. Rojczyk , D. Wagstyl , J. Tumidajski , M. Bojdoł , W. Walas , Z. Halaba , A.J. Nowak
Published: April 2022

In this paper selected heat transfer issues related to the therapeutic hypothermia of newborns are presented and discussed. The therapeutic hypothermia is currently the only well established treatment of newborns suffering for perinatal asphyxia (PA). Considered heat transfer issues are closely associated with the non-invasive thermal measurements carried out at the Department of Anaesthesiology and Intensive Therapy of Children and Newborns of the University Clinic Hospital in Opole, Poland. Obtained results allow for preliminary comparison of the heat transfer processes occurring during both types of therapeutic hypothermia.
Glass beads retro-reflective coating for building application: albedo assessment in urban canyon configurations
Authors: Cardinali Marta , Giuseppe Alessia Di , Gambelli Alberto Maria , Filipponi Mirko , Castellani Beatrice , Nicolini Andrea , Rossi Federico
Published: April 2022

Materials for urban pavements and building coatings have a direct impact on urban thermal environment: low-reflective and highly absorptive materials, in fact, could contribute to the exacerbation of the Urban Heat Island (UHI) phenomenon, which negatively affects building energy consumptions and indoor and outdoor thermal comfort. These effects could be worsened especially in Urban Heat Canyon configurations, where the inter-building effect becomes more relevant. As regards UHI mitigation strategies, high-reflective (HR) and retro- reflective (RR) materials have been studied for their application as urban coatings, in order to provide a cooling effect inside urban canyons. In this framework, this study aims at comparing the albedo performance of HR and RR materials applied on a small scale urban canyon facility. To this aim, an in-field experimental campaign was conducted in two days during summer 2020. Different canyon coating combinations and height/width (H/W) ratios were investigated and compared in terms of albedo. Results show that an albedo worsening occurs when the RR coating was applied to the canyon’s surfaces, because of the lower global reflectance of the RR with respect to the HR. Nevertheless, the application of RR coating on walls, coupled with HR paint on pavement, lead to higher albedo values of up to 4.7%, with respect to the opposite mixed coating combination. Future developments may concern the investigation of the optimum design of a glass bead RR material for building application, by studying the correlation between its optical capabilities and the dimensions and density of the glass beads.
Effect of Different Cooling Methods on Thermal Performance of Single Loop Pulsating Heat Pipe
Authors: Iwata N , Bozzoli F , Cattani L , Pagliarini L , Vocale P
Published: April 2022

A pulsating heat pipe (PHP) is a promising two-phase passive thermal device that consists of a capillary tube meandering between an evaporator and a condenser. Heat is transferred from the evaporator to the condenser by the self-excited oscillation of vapor and liquid. The complete knowledge of the heat transport mechanisms, particularly at the operating limit of PHPs, is far from satisfactory. In PHP, the phase-change acts as a driving force of the self-excited oscillation of the fluid. In this context, the condensation highly affects the performance of PHPs, while few studies have investigated the effect of the sink temperature or the cooling methods. In this study, a single metallic loop is tested to understand the local phenomena focusing on the impact of cooling methods of the condenser section: natural convection and forced air convection. Regardless of the cooling methods, the PHP showed the intermittent and unstable oscillation at low power input just after the start-up, and then continued to operate stably until the heater turned off after the evaporator temperature exceeds 140 °C. The resistance of natural convection cooling is more than 1 K/W lower than that of forced convection cooling, for the same heat input conditions. However, the resistance of both cooling methods at the same evaporator temperature shows a good agreement. The resistance is inversely proportional to the evaporator temperature as well as the heat input.
Study on the local heat transfer behaviour in a flat plate pulsating heat pipe
Authors: Pagliarini Luca , Cattani Luca , Bozzoli Fabio , Slobodeniuk Maksym , Ayel Vincent , Romestant Cyril , Bertin Yves , Rainieria Sara
Published: April 2022

A closed-loop Flat Plate Pulsating Heat Pipe, filled with a water-ethanol mixture (filling ratio = 50% vol.), is tested in horizontal orientation at different heat loads to assess local wall-to-fluid heat fluxes exchanged within its adiabatic section. In addition, the thermal interactions between adjacent channels are investigated since they could be responsible for poorer thermal performances in such kinds of cooling systems. The studied device is obtained from a copper plate (width: 80 mm, length: 200 mm, thickness: 3.5 mm) machined with a single square shaped groove (3 x 3 mm2) forming a series of 8 turns in the evaporator zone and covered with a second copper plate having same length and width, and thickness equal to 0.5 mm. During the Flat Plate Pulsating Heat Pipe operation, the temperature of the external wall, coated with a high-emissivity paint, is monitored within the whole adiabatic section by an InfraRed camera during the pseudo-steady state. The thermographic measurements are post-processed by adopting the Inverse Heat Conduction Problem resolution approach, adequately validated by numerical simulations. The resulting wall-to-fluid heat fluxes are studied in terms of amplitude and oscillation, thus providing novel pieces of information regarding the working behaviour of Flat Plate Pulsating Heat Pipes in terms of oscillatory flow and thermal interactions by conduction between adjacent channels.
Performance Evaluation Criteria for Triangular Microchannels with Smoothed Corners
Authors: Suzzi Nicola , Lorenzini Marco
Published: April 2022

The manufacturing capabilities available today for microchannels make it possible to produce in a comparatively easy, quick and cheap way several cross-sections, possibly allowing modifications of the macro-geometry. Another way is smoothing the corners of polygona cross-sections: this eliminates low-gradient areas and increases transport phenomena, i.e. frictional losses and heat transfer. Several ways of assessing the relative performance of the new shape in comparison to the original have been suggested over the years, among which are Performance Evaluation Criteria (PEC), as proposed by Bergles and Webb. PEC are based on a first-law analysis and aim at extremising the thermal power, heat exchange area, inlet temperature difference or pumping power under varying constraints. In this work equilateral triangular microchannels with uniform wall temperature are considered, through which a liquid flows in fully-developed, steady laminar regime. The cross-sectional area has its corners progressively rounded, and the velocity and temperature profiles are determined, in order to compute the Poiseuille, Nusselt and Stanton numbers, which are then employed in computing the objective functions for some PEC.
Numerical modelization of contact angle hysteresis of falling droplet under enhanced lubrication approximation
Authors: Suzzi Nicola , Croce Giulio
Published: April 2022

Moving contact lines are involved in several engineering applications: in in-flight icing phenomenon, the eventual transition from droplet to rivulet or continuous film regime is crucial for the prediction of ice accretion over the aircraft surface; absorption process through structured packing is also characterized by a thin film flowing over the corrugated sheets. Disjoining pressure together with the assumption of a thin precursor film is largely used in numerical simulations of thin films and moving droplets in order to model the dynamics of moving contact lines and the surface wettability properties, in terms of imposed static contact angle. The disjoining pressure model was largely validated in case of falling films with the well known Voinov-Hoffman-Tanner law. On the other side, the capability of the disjoining pressure to model the contact angle hysteresis, which is a crucial parameter for predicting moving droplets behavior, has not been discussed yet. Here, numerical simulations of both falling films and moving droplets under lubrication approximation are conducted and the disjoining pressure model is used to predict the contact line dynamics. After verification of the full curvature implementation for a 1D falling film, the effective contact angle hysteresis is estimated for a moving droplet under different flow conditions and the transition from droplet to rivulet regime detected.
SRS-based Timepix3 readout system
Authors: Gruber M. , Desch K. , Hemperek T. , Kaminski J. , Richarz L. , Schiffer T.
Published: April 2022

With the combination of the highly granular pixel ASIC Timepix3 by the Medipix3 collaboration and several technologies we are developing a range of detectors. These technologies are bump bonded sensors, microchannel plates (MCP) and photolithographically postprocessed gas amplification stages (InGrid). For example, we are using the combination of the ASIC and an InGrid for the development of X-ray detectors for X-ray polarimetry and for axion search at IAXO. Based on the combination of the ASIC and silicon sensors we are developing a tracker or respectively a beam telescope. The combination of the ASIC and a microchannel plate will be used for neutron detectors. As this range of detectors has several requirements towards the readout and control system and a wide range of designs from low- to high-rate (Hz to MHz) and from single- to multichip, a versatile readout system is needed which adapts these applications without producing too much overhead for the others. To fulfil these requirements, we are developing a modular and scalable readout and control system based on the basil framework — a modular data acquisition system and system testing framework. The fully open-source implementation uses Verilog for the firmware and Python for the software. The system supports several FPGA boards to offer different applications a range of capabilities. One of these FPGA boards is the Scalable Readout System (SRS) by RD51 which offers scalability in low to medium rate applications. For high-rate applications we are working towards the firmware implementation on Xilinx adaptive compute acceleration platform. Besides the scalability, the system offers an optional monitoring interface via a microcontroller for monitoring chip temperatures and power supply voltages. Additionally, further external sensors could be connected to the monitoring system for example via I2C or SPI. For controlling the full system, the software offers a command line interface and a graphical user interface. Both interfaces also include an online event display to monitor the raw data. Additional meta data and data of the monitoring system is stored in a database and can be visualised with a monitoring dashboard.