bluuebunny/crossref_metadata_2025 huggingface dataset:
Amorphous/polycrystalline NiMn selenide for high-performance supercapacitors
Authors: Tang Lun-Qiang , Zhang Kai , Zeng Hong-Yan , Yan Wei , Yue Hong-Li , Wang Ming-Xin
Published: August 2024

Transition-metal selenides have been extensively studied as promising electrode materials for supercapacitors. Engineering amorphous/crystalline heterostructures is an effective strategy to improve rich active sites for accelerating redox reaction kinetics but still lacks exploration. In this study, an amorphous/crystalline heterostructure was designed and constructed by selenizing the self-sacrificial template NiMnS to generate amorphous Mn/polycrystalline Ni0.85Se–NiSe2 heterophase via the phase transformation from metal sulfide into metal selenide. The synergy of the complementary multi-components and amorphous/polycrystalline heterophase could enrich electron/ion-transport channels and expose abundant active sites, which accelerated electron/ion transfer and Faradaic reaction kinetics during charging/discharging. As expected, the optimal NiMnSe exhibited a high specific charge (1389.1 C g−1 at 1 A g−1), a good rate capability, and an excellent lifespan (88.9% retention). Moreover, the fabricated NiMnSe//activated carbon device achieved a long cycle life and energy density of 48.0 W h kg−1 at 800 W kg−1, shedding light on the potential for use in practical applications, such as electrochemical energy-storage devices.
A generalization of the shock invariant relationship
Authors: Horie Yasuyuki , Damm David L.
Published: August 2024

Shock invariant relationship, which was conceived for inert shock waves to derive the 4th power relationship between shock pressure and maximum strain rate, is generalized for reactive shock waves such as Chapman–Jouget detonation and shock-induced vaporization. The generalization, based on the first-order reaction models, is a power function relationship between overall dissipated energy (Δedis) and reaction time Δτ such that ΔedisΔτ1/α=constant, where the power coefficient α is found to be in the range of 2/3–4. Experimental data, though scarce, are consistent with the generalization. Implication of the generalization for inert shocks is also considered and suggests a broad range of the 4th power coefficient including an inequality equation that constrains the shock and particle velocity relationship.
Elastoviscoplastic flows past a cylinder: Fluid-mechanical aspects and dynamic mode decomposition analysis
Authors: Raffi Sana , Chauhan A. , Hamid F. , Sasmal C.
Published: August 2024

When undergoing deformation, elastoviscoplastic fluids exhibit simultaneous viscous, elastic, and plastic characteristics. This study presents an extensive numerical investigation into how the combined elasticity and plasticity of such fluids influence the flow dynamics past a circular cylinder in the laminar vortex-shedding regime. By varying dimensionless numbers, such as the Weissenberg and Bingham numbers, this study elucidates their effects on various fluid-mechanical aspects, including streamlines, vorticity, drag and lift forces, and vortex-shedding frequency. The results show significant differences in the vortex street length, width, and shedding frequency downstream of the cylinder when both fluid elasticity and plasticity are present, compared to Newtonian fluids or fluids with only elasticity under the same flow conditions. Notably, flow field fluctuations are suppressed as fluid elasticity increases, an effect further accentuated by the introduction of fluid plasticity. These rheological behaviors also have a pronounced effect on the drag and lift forces acting on the cylinder. In particular, the drag forces increase with the Weissenberg and Bingham numbers while lift forces decrease. Furthermore, this study conducts the dynamic mode decomposition (DMD) analysis, a widely used reduced order modeling technique, to obtain insights into the coherent flow structures associated with the time-resolved vorticity fields for various fluids. This analysis uncovers hidden differences in the downstream vorticity structures of various fluid types using only a few DMD modes, differences that are not apparent from simple vorticity plots alone. Overall, the findings of this study are valuable for manipulating fluid-dynamical aspects, particularly the vortex-shedding phenomenon from bluff bodies, which is observed in many practical applications and natural processes.
Optimizing structural performance of Savonius turbine blades through comparative analysis of mechanical properties
Authors: Mat Yazik Muhamad Hasfanizam , Ishak Mohammad Hafifi Hafiz , Chang Wei Shyang , Ismail Farzad , Zawawi Mohd Hafiz , Ahmed Ali Najah , Mohd Sidek Lariyah , Basri Hidayah
Published: August 2024

Savonius turbine is an alternative wind turbine design that has the ability for self-starting from static condition at different blade angle. There are concerns in the structural behavior of the materials used for the Savonius turbine blades under aerodynamic loads. This study aims to optimize the structural and material properties of Savonius wind turbine blades by conducting a comparative analysis of maximum stress and deformation across different materials. This research involves creating detailed numerical models of the turbine blades using Finite Element Analysis to simulate the mechanical behavior under operational loads. Wood, Aluminum, and Steel are investigated to examine its effect of structural performance in the static conditions. In addition to solid isotropic materials, anisotropic materials such as Carbon Fiber and Glass Fiber composites are investigated. Ansys Composite Prepost is used to access the mechanical properties of composites. Initial analysis shows that the deformation is highly dependent on the Young's modulus of each material. Due to the dependency of composite on the fiber properties, a multi-objective optimization is defined to optimize these parameters on a five-layer composite structure to minimize stress, deformation, and weight. It was found that Carbon-Fiber composites exhibit better performance compared to other materials with improvement up to 22% in maximum deformation. These findings highlight the potential for substantial improvements in blade efficiency and durability through careful material selection and optimization. These findings can be utilized for a preliminary design of Savonius wind turbines and other renewable energy sector, where optimizing wind turbine performance is crucial for sustainable energy production to find optimum composite configuration without compromising its aerodynamic performance.
Tailoring electrophotonic capabilities of atomically thin GeS through controlled organometallic intercalation
Authors: Iloanya A. C. , Kastuar S. M. , Ekuma C. E.
Published: August 2024

The unique structure of van der Waals materials facilitates a robust mechanism for precise control of physical properties. In this study, we present a comprehensive analysis based on the intercalation of organometallics to modulate the optoelectronic behavior of two-dimensional germanium sulfide (GeS). Advanced computational exploration reveals significant and tunable features in the intercalated material. Additionally, the weak chemical interactions between organometallics and GeS support the electric-field-mediated drift and charge–discharge processes in intercalants. Controlling the concentration of organometallics in this manner enables the dynamic emergence of novel characteristics post-intercalation. These include flatbands near the Fermi level, significant enhancement of carrier mobility, and a magnetic ground state that is atypical for pristine GeS. Our findings demonstrate that organometallic intercalation offers a powerful strategy for tailoring the optoelectronic and magnetic characteristics of GeS, paving the way for harnessing emerging features for applications in next-generation devices.
Drag reduction performance of binary polyacrylamide and xanthan gum solutions
Authors: Gu Haoyu , Shi Pengfei , Liu Hao , Hu Haibao , Wen Jun , Zhu Tao , Xie Luo
Published: August 2024

Flexible polymers exhibit pronounced drag reduction but weak resistance to mechanical shear, whereas rigid polymers exhibit remarkable resistance to mechanical shear but slightly weaker drag reduction. Therefore, mixing flexible and rigid polymers could offer improvements in comprehensive drag-reduction performance. This letter reports an experimental study on the drag-reduction performance of binary polyacrylamide (PAM) and xanthan gum (XG) solutions with the PAM concentration fixed at 10 ppm. From comparing curves of the drag reduction rate vs Reynolds number and shearing time, 70-ppm XG is the optimal choice for forming a binary polymer solution with 10-ppm PAM. This binary solution also offers drag-reduction effects equivalent to those of a pure 50-ppm PAM solution. Although it decreases with time, the synergistic coefficient still remains much larger than zero. This implies that the positive synergistic effect of the PAM–XG binary solution persists even under long-term shearing. These results offer a fundamental basis for developing high-performance polymer drag reducers.
Research facilities strive for fair and efficient time allocation
Authors: Feder Toni
Published: August 2024

Distributed evaluations, machine learning, and lotteries are among the tactics being tested to improve the process and integrity of peer review.
The cyclobutene diester approach to alkyl citrate natural products
Authors: Rossouw Nikolai P. , Rizzacasa Mark A.
Published: August 2024

This review outlines the synthesis of alkyl citrate natural products using cyclobutene diester precursors. The approach is efficient and stereoselective and provides the correct oxidation state of the citrate core of these compounds. The synthesis of a number of alkyl citrates along with some higher oxidised members of this family is detailed.
Rediscovering the human thymus through cutting-edge technologies
Authors: Pala Francesca , Notarangelo Luigi D. , Bosticardo Marita
Published: August 2024

Recent technological advances have transformed our understanding of the human thymus. Innovations such as high-resolution imaging, single-cell omics, and organoid cultures, including thymic epithelial cell (TEC) differentiation and culture, and improvements in biomaterials, have further elucidated the thymus architecture, cellular dynamics, and molecular mechanisms underlying T cell development, and have unraveled previously unrecognized levels of stromal cell heterogeneity. These advancements offer unprecedented insights into thymic biology and hold promise for the development of novel therapeutic strategies for immune-related disorders.
Deciphering TADF Mechanisms in Metal-Free Organic Emitters BrA-HBI: Utilizing Optimally Tuned Range-Separated Functionals for Insight
Authors: Yu 于 Chunyue 春悦 , Yin 尹 Hang 航 , Guo 郭 Jie 婕 , Zhang 张 Wentian 闻天 , Shi 石 Ying 英
Published: August 2024

Metal-free organic emitters, characterized by their thermally activated delayed fluorescence (TADF) properties, offer considerable promise for the creation of highly efficient organic light-emitting diodes (OLEDs). Recently, Shao et al. presented a novel excited state intramolecular proton transfer (ESIPT) system BrA-HBI, demonstrating an emission quantum yield of up to 50% [Adv. Funct. Mater.
32, 2201256 (2022)]. However, many open issues cannot be answered solely by experimental means only and require detailed theoretical investigations. For instance, what causes the activation of TADF from the Keto* tautomer and leads to fluorescence quenching in the Enol* form? Herein, we provide a theoretical investigation on the TADF mechanism of the BrA-HBI molecule by optimally tuned range-separated functionals. Our findings reveal that ESIPT occurs in the BrA-HBI molecule. Moreover, we have disclosed the reason for the fluorescence quenching of the Enol* form and determined that the T
2 state plays a dominant role in the TADF phenomenon. In addition, double hybrid density functionals method was utilized to verify the reliability of optimally tuned range separation functionals on the calculation of the TADF mechanism in BrA-HBI. These findings not only provide a theoretical reference for development of highly efficient organic light-emitting diodes, but also demonstrate the effectiveness of the optimally tuned range-separated functionals in predicting the luminescence properties of TADF molecules.
Hidden symmetries of power-law inflation
Authors: Chiba Takeshi , Houri Tsuyoshi
Published: August 2024

A scalar field with an exponential potential has been proposed as a model of inflation (called power-law inflation). Although it admits an exact solution, the integrability of the system has not been shown. We uncover the hidden symmetries behind the system by utilizing the Eisenhart lift of field theories. We find that a conformal Killing vector field in the field space exists only for a particular combination of exponential functions that includes a single exponential potential. This implies the existence of additional conserved quantity and explains the integrability of the system.
Self-interactions can (also) destabilize bosonic stars
Authors: Brito Marco , Herdeiro Carlos , Sanchis-Gual Nicolas , dos Santos Costa Filho Etevaldo , Zilhão Miguel
Published: August 2024

We study the dynamical stability of Proca-Higgs stars, in spherical symmetry. These are solutions of the Einstein-Proca-Higgs model, which features a Higgs-like field coupled to a Proca field, both of which minimally coupled to the gravitational field. The corresponding stars can be regarded as Proca stars with self-interactions, while avoiding the hyperbolicity issues of self-interacting Einstein-Proca models. We report that these configurations are stable near the Proca limit in the candidate stable branches, but exhibit instabilities in certain parts of the parameter space, even in the candidate stable branches, regaining their stability for very strong self-interactions. This shows that for these models, unlike various examples of scalar boson stars, self-interactions can deteriorate, rather than improve, the dynamical robustness of bosonic stars.
Gauge-invariant magnetic charges in linearised gravity
Authors: Hull Chris , Hutt Maxwell L , Lindström Ulf
Published: August 2024

Linearised gravity has magnetic charges carried by (linearised) Kaluza–Klein monopoles. A gauge-invariant expression is found for these charges that is similar to Penrose’s gauge-invariant expression for the ADM charges. A systematic search is made for other gauge-invariant charges.
Comparing eccentric waveform models based on post-Newtonian and effective-one-body approaches
Authors: Kacskovics Balázs , Barta Dániel
Published: August 2024

In the present study, two numerical models were compared to each other, namely the CBWaves and SEOBNRE algorithms, developed using the post-Newtonian and effective-one-body approaches, respectively, for the study of binary black holes evolving on eccentric orbits. To map the mismatch between the two models 260 000 simulations were conducted – 20 000 for non-spinning configurations and 240 000 for spinning ones—on a common grid of parameter values over the parameter space. This space is defined by the mass ratio

q
≡

m
1

/

m
2

∈
[
0.1
,

1
]

, the gravitational mass

m
i

∈
[
10

M
⊙

,

100

M
⊙

]

of each component labeled by i, the corresponding spin magnitude

S
i

∈
[
0
,

0.6
]

and a constant initial orbital eccentricity e
0. A comprehensive investigation was conducted to determine whether there was a discrepancy in the waveforms generated by the two codes. This entailed an in-depth analysis of the mismatch, and an extensive comparison was carried out on the outlier points between the two codes.
Protocols for x-ray transient grating pump/optical probe experiments at x-ray free electron lasers
Authors: Fainozzi Danny , Cucini Riccardo , Vila-Comamala Joan , Lima Frederico , Ardana-Lamas Fernando , Bañares Luis , Bargheer Matias , Bencivenga Filippo , Berndt Nadia , Beye Martin , Biednov Mykola , Bonetti Stefano , Brioschi Marta , Cannizzo Andrea , Carrara Pietro , Chergui Majed , David Christian , Engel Robin Y , Ferrari Eugenio , Feurer Thomas , Frankenberger Paul , Gawelda Wojciech M , Gessini Alessandro , Heder Siti , Huang Xinchao , Khatu Nupur N , Knoll Martin , Madsen Anders , Mamyrbayev Talgat , Masciovecchio Claudio , Maznev Alexei A , Milne Christopher , Mincigrucci Riccardo , Nelson Keith A , Paltanin Ettore , Rossi Giorgio , Scholz Markus , Serrat Carles , Staub Urs , Szlachetko Jakub , Torre Renato , Dhanalakshmi-Veeraraj Mano R , Xu Han , Zalden Peter , Svetina Cristian
Published: August 2024

Transient grating spectroscopy is a specialized application of the four-wave-mixing methodology and constitutes a versatile technique for investigating the dynamics of vibrational, magnetic and electronic degrees of freedom of matter in a background-free fashion. Recent developments in free-electron laser sources have enabled the extension of this technique into the extreme ultraviolet range. Ongoing efforts to expand transient grating spectroscopy into the x-ray regime promise numerous advantages: (1) substantial penetration depths that allow for probing bulk material properties, (2) element specificity via specific core-excited states, and (3) short wavelengths that allow for excitation gratings with higher momentum transfer and improved spatial resolution. In this study, we comprehensively outline the procedures for conducting x-ray transient grating pump/optical probe experiment. The process encompasses the design and alignment of the experimental setup, as well as the subsequent steps involved in data acquisition and analysis. This paper is intended as a comprehensive guide for researchers interested in implementing x-ray transient grating spectroscopy, providing valuable insights into the intricacies of the experimental workflow required for this novel technique. Furthermore, we discuss the potential for extending this methodology to an x-ray pump/x-ray probe scheme, envisioning a future direction that holds promise for enhancing the capabilities and scope of x-ray transient grating spectroscopy, opening new opportunities for studying ultrafast processes with unprecedented temporal and spatial resolutions.
Non-itinerant-type ferromagnetism and the magnetocaloric response of quinary all-d-metal ribbon: Ni35Mn34.5Co14Fe1Ti15.5
Authors: Mandal Sourav , Nath Tapan Kumar
Published: August 2024

Most of the ferromagnetic shape memory (FSM) Heusler alloys, which are primarily studied in bulk form in the literature, exhibit p-d type hybridization. This study conducts a thorough multidirectional investigation of a strongly d-d hybridized quinary melt-spun annealed ribbon having the composition Ni35Mn34.5Co14Fe1Ti15.5 (NMCFT-1). This off-stoichiometric, polycrystalline FSM, fabricated using the melt-spin technique, exhibits a highly textured microstructure, double magnetic transitions and super-mechanical features mitigating brittleness. It crystallizes in a perfectly B2-type disorder austenite (Pm-3m, space group number 221) phase at room temperature. It has been hypothesized that geometric frustration is the causative factor for this disorder. Curie temperature of austenite phase (

T

C

A

) between paramagnetic → ferromagnetic state is found to be ∼364.57 K, whereas martensite transformation temperature from weak magnetic martensite state to ferromagnetic austenite state is ∼174.74 K. Calculated moments (effective moment,

μ

eff

= 5.12

μ

B

; low-temperature saturation moment,

μ

S

(or

M

S

(
0
)

) = 5.08

μ

B

) yield a Rhodes–Wohlfarth ratio of ∼1, indicating the existence of the non-itinerant nature of 3d electrons, whereas the ferromagnetism and the linear or non-linear dependency of

M

s

2

(
T

) on T
2 around

T

C

A

indicates the presence of long-range Rudermann–Kittel–Kasuya–Yosida-type interaction. More importantly, the maximum magnetic entropy change (

Δ

S

m

) obtained across the first-order magneto-structural transition and second-order magnetic transition are +18.2 J·kg−1K−1 at 6 T and −8.8 J·kg−1K−1 at 2 T, respectively, while a very high working temperature span (ΔT
FWHM) of 28.561 K and 6.922 K are found for the same condition. The sample exhibits a significant relative cooling power of 402.98 J·kg−1 at a magnetic field of 6 T across the FOMT and 60.19 J·kg−1 at a 2 T field across the SOMT, respectively, along with excellent mechanical features such as a Vickers hardness (HV) of 411.80 HV (∼4.04 GPa). Meanwhile, Chen’s super hard model fails to predict the ribbon’s HV value, but Miao’s hard model does, indicating that the ribbon is hard but not super hard. It also paves the way for additional investigation into innovative FSMs like this.
Oxygen vacancies kinetics in TaO

2
−
h

/Ta2O

5
−
x

memristive interfaces
Authors: Ferreyra C , Leal Martir R , Rubi D , Sánchez M J
Published: August 2024

Oxygen vacancies (OV) are pervasive in metal oxides and play a pivotal role in the switching behaviour of oxide-based memristive devices. In this study we address OV dynamics in Pt/TaO

2
−
h

/Ta2O

5
−
x

/TaO

2
−
y

/Pt devices, through a combination of experiments and theoretical simulations, In particular, we focus on the RESET transition (from low to high resistance) induced by the application of electrical pulse(s), by choosing different initial OV profiles and studying their kinetics during the mentioned process. We demonstrate that by selecting specific OV profiles it is possible to tune the characteristic time-scale of the RESET. Finally, we show that the implementation of gradual RESETs, induced by applying many (small) successive pulses, allows estimating the activation energies involved in the OV electromigration process. Our results help paving the way for OV engineering aiming at optimizing key memristive figures such as switching speed or power consumption, which are highly relevant for neuromorphic or in-memory computing implementations.
Heusler alloy Mn2CoAl: structural, magnetic and electronic properties
Authors: Yang J Y , Xiang X J , Tan Z J , Zhang X K , Pan S , Chen J , Xu G Z
Published: August 2024

In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μ
B at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl.
Low-current gliding DC discharge in high-speed flows
Authors: Kornev K N , Logunov A A , Dvinin S A
Published: August 2024

A low-current gliding discharge (current range 1–5 A) in high-speed air flows of 100–250 m s−1 was experimentally studied. A high-voltage direct current source with a maximum voltage of 4.5 kV was used to create the discharge. The average electron concentration n
e ∼ 1014 cm−3 and the plasma ionization degree were determined by measuring the Stark broadening of the hydrogen H
β
line (λ
Hβ
= 486.1 nm). The estimates of the electric field (E ∼ 100 V cm −1 ÷ 600 V cm−1) in the discharge positive column were found using time-synchronized high-speed video recordings and oscillograms. The gas rotational temperature T
g = 7000–9500 K and the vibrational temperature T
v = 7000–11 000 K were estimated using optical emission spectroscopy. Time-resolved spectroscopy is used to investigate the effective plasma channel spatial regions from which the N, NH, N2
+, O and OH molecules radiate. The difference of the obtained radii indicates the presence of a radial temperature gradient and inhomogeneous plasma composition in the discharge cross section. The possibility of using of gliding discharge to ignite hydrocarbon-air mixtures in the ramjet engines combustors has been experimentally demonstrated.
A 85Rb transverse modulation magnetometer in the geophysical range based on atomic alignment states
Authors: Shi Tao , Jin Ge , Zhang Hong , Zou Sheng
Published: August 2024

We have constructed a transverse modulated magnetometer based on spin alignment in a paraffin-coated 85 Rb cell operated in a geophysical magnetic field of 47.1 µT. When an orthogonal driving magnetic field (

x
^

axis) is resonant on the Larmor frequency (

z
^

axis), we have proposed a new method to zero the static residual magnetic fields in the transverse plane and achieved a sensitivity of

1.8
 

pT

Hz

−
1

with bandwidth of 200 Hz. The repump light (

F

g

=
2
→

F

e

=
2

) redistributes the populations in the ground state, rendering the state

|

F

g

=
2
⟩

dark. This effect significantly amplifies the optical rotation signals nearly fourfold. The numerical solution of the Liouville equation is in good agreement with the experimental results. By using perturbation treatment and employing appropriate approximations, the derived analytical expressions for optical rotation are deduced to succinctly elucidate the dynamics of atomic alignment under parametric modulation. These outcomes could be extended for the advancement of an alignment magnetometer that has been designed to detect a weak magnetic signal in the geophysical range.
Magnetism of pseudospin-1/2 pyrochlore antiferromagnet Na3Co(CO3)2Cl
Authors: Nawa Kazuhiro , Murasaki Ryo , Itoh Shinichi , Saito Hiraku , Nojiri Hiroyuki , Dela Cruz Clarina , Okuyama Daisuke , Yoshida Masahiro , Ueta Daichi , Yoshizawa Hideki , Sato Taku J
Published: August 2024

Pyrochlore magnets have attracted interest as systems for realizing critical phenomena, rich magnetic structures, associated topological band structures, and nontrivial quantum phases. Na3Co(CO3)2Cl is a pseudospin-1/2 antiferromagnet in which the Co2+ ions form a pyrochlore network. Its structural and magnetic properties were investigated using magnetization, heat capacity, ESR, single-crystal x-ray diffraction, powder neutron diffraction and powder inelastic neutron scattering. Magnetization and heat capacity measurements indicated a ground-state doublet, which is regarded as pseudospin 1/2, dominated the magnetic properties at low temperatures, with a magnetic exchange of 9.6 K. As the temperature decreases, a magnetic transition is observed at 1.6 K, which is confirmed to be an all-in-all-out magnetic order. The crystal field excitations observed by inelastic neutron scattering experiments indicated the Ising nature of the ground-state doublet. This thorough study revealed that Na3Co(CO3)2Cl can be regarded as a pseudospin-1/2 pyrochlore lattice antiferromagnet with dominant Ising-type interactions.
Object registration techniques for 3D particle tracking
Authors: Hendriksen L A , Sciacchitano A , Scarano F
Published: August 2024

Image based three-dimensional (3D) particle tracking is currently the most widely used technique for volumetric velocity measurements. Inspecting the flow-field around an object is however, hampered by the latter, obstructing the view across it. In this study, the problem of measurement limitations due to the above is addressed. The present work builds upon the recent proposal from Wieneke and Rockstroh (2024 Meas. Sci. Technol.
35 055303), whereby the information of the occluded lines of sight can be incorporated into the particle tracking algorithm. The approach, however, necessitates methods that accurately evaluate the shape and position of the object within the measurement domain. Methods of object marking and the following 3D registration of a digital object model (CAD) are discussed. For the latter, the iterative closest point registration algorithm is adopted. The accuracy of object registration is evaluated by means of experiments, where marking approaches that include physical and optically projected markers are discussed and compared. Three objects with growing level of geometrical complexity are considered: a cube, a truncated wing and a scaled model of a sport cyclist. The registered CAD representations of the physical objects are included in aerodynamic experiments, and the flow field is measured by means of large-scale particle tracking using helium filled soap bubbles. Results indicate that object registration enables a correct reconstruction of flow tracers within regions otherwise affected by domain clipping as a consequence of obstructed camera lines-of-sight. Finally, the combined visualization of the object and the surrounding flow pattern offers means of insightful data inspection and interpretation, along with posing a basis for particle image velocimetry data assimilation at the fluid-solid interface.
Phase fraction measurement of gas-liquid flow based on cyclonic capacitive sensor (CCS) and inverse drift flux method
Authors: Yuan Chao , Wang Jinghan , Xu Ying
Published: August 2024

As the demand for clean energy sources like natural gas increases, the need for methods to measure the phase fraction of gas-liquid two-phase flows, which have complex and variable flow patterns, becomes more pronounced. This study introduces a phase fraction measurement method based on a cyclonic capacitive sensor. An effective phase fraction prediction model for the gas-liquid flow measurement section is established based on the capacitive signals. Using the drift flux principle, the dimensionless drift velocity of the spiral annular flow is analyzed, and a volume gas fraction (GVF) prediction model based on the ‘inverse drift flux method’ is established. Experimental results show that this method is suitable for a wide range of phase fraction measurements and is highly accurate. When the liquid volume fraction (LVF) is less than 10%, the average relative error of the predicted GVF is 0.3%; for the LVF from 10% to 30%, the average relative error is 1.4%.
Noise reduction method for wind turbine gearbox vibration signals based on CVMD-DRDSAE
Authors: Yao Jinbao , Yue Bohao , Wang Yizhu , Li Xiang
Published: August 2024

Wind turbine gearbox fault feature extraction is difficult due to strong background noise. To address this issue, a noise reduction method combining comprehensive learning particle swarm optimization-variational mode decomposition (CLPSO-VMD) and deep residual denoising self-attention autoencoder (DRDSAE) is proposed. Firstly, the proposed CLPSO-VMD algorithm is used to decompose the noisy wind turbine gearbox vibration signals. Subsequently, the intrinsic mode functions highly correlated with the original signals are selected through the Spearman correlation coefficient and utilized for signal reconstruction, thereby filtering out high-frequency noise outside the fault frequency band in the frequency domain characterization. Secondly, the improved DRDSAE is utilized to learn the latent representations of data in the first-level denoised signal, further reducing the residual noise within the fault frequency band while retaining important signal features. Finally, the envelope spectrum highlights the weak feature of the wind turbine gearbox vibration signal. Experimental results demonstrate the effectiveness of the proposed method in denoising wind turbine gearbox vibration signals under strong noise.
Dynamically adaptive cascading updates for hierarchical digital twins
Authors: Guo Haoyu , Wang Shaoping , Shi Jian , Niu Yu , Lizzio Fausto , Guglieri Giorgio
Published: August 2024

Traditional sensors encounter challenges such as high collection costs, insufficient measurement points, and low data quality in the monitoring and maintenance of modern equipment. These challenges significantly affect the effectiveness and efficiency of monitoring and maintenance processes. Digital twin (DT) technology, as a digital replica of physical entities, is regarded as the ‘digital sensor’ of physical entities due to its high-precision modeling and dynamic updating capabilities. Compared to traditional sensors, DT models provide substantial improvements in both data volume and quality. However, creating a DT model with high precision and robust dynamic characteristics is notably challenging, particularly when the relationships and state features of the physical entity are complex and variable. To address this issue, a cascading update strategy was introduced. This strategy coordinates complex hierarchical DT update tasks, ensuring model accuracy. Furthermore, a signal characteristic-based dynamic adaptive update algorithm is proposed. This algorithm optimizes the DT updating process and enhances the model’s dynamic characteristics. The proposed method is validated using experimental data on plunger pump barrel-port plate oil leakage. The results demonstrate that the method significantly improves the accuracy and updating efficiency of the DT model. It achieves a balance between precision and update time costs, enhancing DTs accuracy and practicality as a ‘digital sensor’.
Projected moving patterns for reference-free background-oriented schlieren technique (BOS)
Authors: Raffel Markus , Smith Nathanial T , Wolf C Christian , Heineck James T , Gardner Anthony D
Published: August 2024

A background-oriented schlieren technique (BOS) using projected background patterns is presented. The projected backgrounds can be scaled to the measurement requirements, providing greater flexibility than printed backgrounds. The evaluation of the BOS image pairs using cross-correlation or optical flow analysis was demonstrated to produce equivalent results. The background pattern can dynamically be shifted by a rotating mirror, allowing evaluation using the reference-free shadowgraphy or reference-free BOS methods. The forward BOS technique is demonstrated, in which a projected speckle pattern is illuminated through a density object and recorded by a camera focused on the screen. In contrast to standard shadowgraphy, where the local image intensity is the parameter proportional the second derivative of density, this technique is robust with respect to varying lighting of the field as long as the displacement of small-scale image structures can be determined.
Nanosized-laser-induced sub-20 nm homogenous alloy nanoparticles
Authors: Zhang Chen , Wang Shu , Yang Yaqi , Jiang Chuanxiu , Liu Xinfeng , Liu Qian
Published: August 2024

Alloy nanoparticles (NPs) have great potential in nanosized 3D-printing, surface coating, plasmonic enhancement, information coding, and so forth. However, chemical-pollution-free and homogeneous sub-20 nm NPs maintain still a challenge in preparation. Here we present a smart nanosecond laser scan strategy of alloy-NPs preparation on a bilayer metal film by using a nanosized focused beam, successfully realizing controllable fabrication of the sub-20 nm homogeneous alloy NPs without pollution. As a demonstration, various sub-20 nm AgCu NPs with different volume ratios have been prepared, all NPs show narrow size distribution and uniform interparticle spacing. This simple and cost-effective method is stable and adaptable for other alloy-NPs such as AuAg NPs. In addition, such alloy NPs exhibit two-peak plasma resonance feature and information coding capacity. We believe that homogenous alloy sub-20 nm NPs will provide new application opportunities in many fields.
Imaging the adsorption sites of organic molecules on metallic surfaces by an adaptive tunnelling current feedback
Authors: Martin-Jimenez Daniel , Zhong Qigang , Schirmeisen André , Ebeling Daniel
Published: August 2024

Atomic force microscopy (AFM) allows submolecular resolution imaging of organic molecules deposited on a surface by using CO-functionalized qPlus sensors under ultrahigh vacuum and low temperature conditions. However, the experimental determination of the adsorption sites of these organic molecules requires the precise identification of the atomic structure of the surface on which they are adsorbed. Here, we develop an automation method for AFM imaging that provides in a single image both, submolecular resolution on organic molecules and atomic resolution on the surrounding metallic surface. The method is based on an adaptive tunnelling current feedback system that is regulated according to the response of the AFM observables, which guarantees that both the molecules and the surface atoms are imaged under optimum conditions. Therewith, the approach is suitable for imaging adsorption sites of several adjacent and highly mobile molecules such as 2-iodotriphenylene on Ag(111) in a single scan. The proposed method with the adaptive feedback system facilitates statistical analysis of molecular adsorption geometries and could in the future contribute to autonomous AFM imaging as it adapts the feedback parameters depending on the sample properties.
Micelles of poly[oligo(ethylene glycol) methacrylate] as delivery vehicles for zinc phthalocyanine photosensitizers
Authors: Kara Merve , Kocaaga Nagihan , Akgul Busra , Abamor Emrah S , Erdogmus Ali , Topuzogullari Murat , Acar Serap
Published: August 2024

Drug-loaded polymeric micelles have proven to be highly effective carrier systems for the efficient delivery of hydrophobic photosensitizers (PSs) in photodynamic therapy (PDT). This study introduces the micellization potential of poly(oligoethylene glycol methyl ether methacrylate) (pOEGMA) as a novel approach, utilizing the hydrophobic methacrylate segments of pOEGMA to interact with highly hydrophobic zinc phthalocyanine (ZnPc), thereby forming a potential micellar drug carrier system. The ZnPc molecule was synthesized from phthalonitrile derivatives and its fluorescence, photodegradation, and singlet oxygen quantum yields were determined in various solvents. In solvents such as tetrahydrofuran, dimethyl sulfoxide, and N,N-dimethylformamide, the ZnPc compound exhibited the requisite photophysical and photochemical properties for PDT applications. The pOEGMA homopolymer was synthesized via reversible addition-fragmentation chain-transfer polymerization, while ZnPc-loaded pOEGMA micelles were prepared using the nanoprecipitation method. Characterization of the pOEGMA, ZnPc, and micelles was conducted using FTIR, 1H-NMR, dynamic light scattering, matrix-assisted laser desorption/ionization time-of-flight mass spectrometries, gel permeation chromatography, and transmission electron microscopy. The critical micelle concentration was determined to be 0.027 mg ml−1 using fluorescence spectrometry. The drug loading and encapsulation efficiencies of the ZnPc-loaded micelles were calculated to be 0.67% and 0.47%, respectively. Additionally, the release performance of ZnPc from pOEGMA micelles was monitored over a period of nearly 10 d, while the lyophilized micelles exhibited stability for 3 months. Lastly, the ZnPc-loaded micelles were more biocompatible than ZnPc on L929 cell line. The results suggest that the pOEGMA homopolymer possesses the capability to micellize through its methacrylate segments when interacting with highly hydrophobic molecules, presenting a promising avenue for enhancing the delivery efficiency of hydrophobic PSs in PDT. Moreover, it was also deciphered that obtained formulations were highly biocompatible according to cytotoxicity results and could be safely employed as drug delivery systems in further applications.
How a soup bowl and a coffee cup cool down
Authors: Ferreira João Paulo M
Published: August 2024

The cooling of liquid foods held in plates, bowls, or cups is an event encountered several times a day. Here, it is reported a simple practical activity that demonstrates the role played by different heat transfer mechanisms in that process. The experiments can be done even at home with basic kitchenware. The demonstrations show the important role of evaporative cooling in many cases, versus convection and radiation. In this work, the applicability of Newton’s law of cooling is verified, the contributions of the different heat transfer mechanisms are quantified, and values of heat transfer coefficients are estimated. However, the data analyses and the discussions of the results can be adjusted to different audiences.
A neural network for the analysis of Langmuir-probe characteristics
Authors: Joshi-Thompson Jasmin , Ramisch Mirko
Published: August 2024

Langmuir probes have been widely used in the field of plasma diagnostics for the characterisation of plasma properties. These probes play a crucial role in understanding the behaviour of a diverse range of plasmas, e.g.  edge plasmas in fusion experiments. The measurement of electron density (ne
) and electron temperature (Te
) provides valuable insights into the plasma’s state, stability, and confinement properties. Conventionally, this analysis involves post-experiment fitting methods to calculate plasma properties from the measured current–voltage curves obtained from Langmuir probes. This work introduces a neural-network approach for analysing probe data from the TJ-K stellarator, allowing for fast associative plasma characterisation. The results show a reliable performance on test data within the domain of the training set, predicting both ne
and Te
within the 10 % intrinsic error. Performance on unseen data outside the domain of the training set was on average within a 26 % and 21 % error on ne
and Te
, respectively. The network’s further abilities, including the identification of low-quality and falsely-labelled data, were also explored. The use of neural networks (NNs) offers fast predictions, enabling further research into real-time applications and live feedback control. This paper highlights the promising role of NNs in enhancing the analysis of Langmuir-probe characteristics.
Investigation of high-speed superconducting electric machines through time-space extrusion numerical modelling
Authors: Zhang Hongye
Published: August 2024

Featured by high power density and efficiency, high temperature superconducting (HTS) electric machines provide a promising solution to heavy-duty electric transport, e.g. electric aircraft. However, designing HTS machines, particularly high-speed HTS motors, presents significant challenges: (1) modelling is highly time-consuming due to the non-linear resistivity of superconductors and complex machine topology; (2) accurately estimating the AC loss of HTS windings remains an open aspiration due to the complicated AC environment. To reduce computational complexity, the thin film approximation (only considering the approximated 1-D HTS film) for HTS coated conductors (CCs) has been widely adopted in simulations, such as the T-formulation models; however, the thin film approximation becomes inadequate for HTS CCs under high-frequency magnetic fields, as encountered in high-speed motors for aerospace. To efficiently and accurately model the AC loss of HTS windings in high-speed superconducting machines, taking a 1 MW superconducting synchronous motor with HTS armature windings as an example, this paper has adopted a time-space extrusion (TSE) method, which demonstrates a >25-fold decrease in modelling time while maintaining comparable accuracy to two benchmark H-A models. The power dissipation in both normal-conducting and superconducting layers of HTS windings has been studied, the AC losses in different turns of the armature winding have been explored, and the slot leakage field harmonics have been illustrated. Results have shown that the losses in Cu and Ag layers for high-speed HTS machines operating at cryo-temperatures (e.g. liquid hydrogen temperature) are not neglectable, especially with a high residual resistance ratio and in the presence of harmonics. The HTS armature winding should be positioned away from the iron tooth and slot opening to minimise exposure to slot leakage fields. The adopted TSE modelling strategy and drawn conclusions have provided valuable insights for the efficient design of high-speed superconducting machines.
Tighter upper bounds on the critical temperature of two-dimensional superfluids and superconductors from the BCS to the Bose regime
Authors: Shi Tingting , Zhang Wei , Sá de Melo C A R
Published: August 2024

We discuss standard and tighter upper bounds on the critical temperature

T
c

of two-dimensional superfluids and superconductors versus particle density n or filling factor ν for continuum and lattice systems from the Bardeen–Cooper–Schrieffer (BCS) to the Bose regime. We consider only one-band Hamiltonians, where the transition from the normal to the superfluid (superconducting) phase is governed by the Berezinskii–Kosterlitz–Thouless (BKT) mechanism of vortex-antivortex binding, such that a direct relation between the superfluid density tensor and

T
c

exists. The standard critical temperature upper bound

T
c

up
1

is obtained from the Ferrell-Glover-Tinkham sum rule for the optical conductivity, which constrains the superfluid density tensor components. We demonstrate that it is imperative to consider at least the full effect of phase fluctuations of the order parameter for superfluidity (superconductivity) and use the renormalization group to obtain the phase-fluctuation critical temperature

T
c

θ

, a much tighter bound to the critical temperature supremum than

T
c

up
1

over a wide range of densities or filling factors. We also discuss a fundamental difference between superfluids and superconductors in regards to the vortex core energy dependence on density. Going beyond phase fluctuations, we note that theories including modulus fluctuations of the order parameter or particle-hole fluctuations valid throughout the BCS-Bose evolution are still lacking, but the inclusion of these fluctuations can only produce a critical temperature that is lower than

T
c

θ

and thus produce an even tighter bound to the critical temperature supremum. We conclude by indicating that if the measured critical temperature exceeds

T
c

θ

in experiments involving two-dimensional single-band systems, then a non-BKT mechanism must be invoked to describe the superfluid (superconducting) transition.
Investigation of microstructure and mechanical properties of Al-Si alloy thin walled cylindrical part fabricated by CMT based WAAM process
Authors: Nanjundan Annamalai , Natarajan U , Simson D
Published: August 2024

Wire Arc Additive Manufacturing (WAAM) represents a major advancement in the production of large-scale metal components. WAAM is recognized for its capacity to produce components with enhanced material properties and structural integrity compared to conventional manufacturing processes. As WAAM involves layer-by-layer fabrication, the resulting components exhibit a higher degree of anisotropy in microstructural and mechanical properties. Additionally, the properties of WAAM components can vary significantly in terms of microstructure and mechanical performance along the build direction of the multi-layered parts. This study investigates the mechanical and microstructural properties of thin-walled cylinder made from Al-Si (Al 4043) alloy using CMT-WAAM. The analysis aims to elucidate the factors contributing to variations in these properties and provide insights into the underlying reasons for observed discrepancies. The micro hardness, tensile strength, and impact strength are analysed at both bottom and top region of the thin walled cylinder. The microhardness, tensile strength, and impact strength of the bottom region are 14.51%, 3.14%, and 12.19% less than those of the top region, respectively, due to the repeated thermal cycles during subsequent layer deposition. Fractographic analysis indicates a ductile fracture mode, characterized by the presence of dimples and microvoid coalescence. Further, the microstructural analysis reveal that top region consists fine grain compared to bottom region of thin-walled cylinder. X-ray Diffraction (XRD) analysis identified secondary phase particles, such as MgSi2 and Al9Si, at the grain boundaries, which was further confirmed by EDS analysis. These microstructural changes and the presence of secondary phases are reasons for the changes in the mechanical properties along build direction.