bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-driven ultrafast impedance spectroscopy for measuring complex ion hopping processes
Authors: Pham Kim H. , Lin Amy K. , Spear Natan A. , Cushing Scott K.
Published: July 2024

Superionic conductors, or solid-state ion-conductors surpassing 0.01 S/cm in conductivity, can enable more energy dense batteries, robust artificial ion pumps, and optimized fuel cells. However, tailoring superionic conductors requires precise knowledge of ion migration mechanisms that are still not well understood due to limitations set by available spectroscopic tools. Most spectroscopic techniques do not probe ion hopping at its inherent picosecond timescale nor the many-body correlations between the migrating ions, lattice vibrational modes, and charge screening clouds—all of which are posited to greatly enhance ionic conduction. Here, we develop an ultrafast technique that measures the time-resolved change in impedance upon light excitation, which triggers selective ion-coupled correlations. We also develop a cost-effective, non-time-resolved laser-driven impedance method that is more accessible for lab-scale adoption. We use both techniques to compare the relative changes in impedance of a solid-state Li+ conductor Li0.5La0.5TiO3 (LLTO) before and after UV to THz frequency excitations to elucidate the corresponding ion-many-body-interaction correlations. From our techniques, we determine that electronic screening and phonon-mode interactions dominate the ion migration pathway of LLTO. Although we only present one case study, our technique can extend to O2−, H+, or other charge carrier transport phenomena where ultrafast correlations control transport. Furthermore, the temporal relaxation of the measured impedance can distinguish ion transport effects caused by many-body correlations, optical heating, correlation, and memory behavior.
The study of interaction of the high energetic plasma and electron pulses with multicomponent alloy surface
Authors: Nowakowska-Langier K. , Barlak M. , Malinowska A. , Zaloga D. , Romaniuk S. , Kwiatkowski R. , Minikayev R. , Namyslak K.
Published: July 2024

This paper investigates the impact of high-energy sources, namely, high-energy plasma pulses and high-energy electron beam pulses, on materials in the form of layer through separate and combined exposures. Experimental setups utilizing a Rod Plasma Injector (RPI) and an electron gun were employed for irradiation tests. The studies involved pre- and post-treatment analysis of morphology, chemical, and phase composition using scanning electron microscopy and x-ray diffraction measurements. Surface modifications under different exposure conditions were characterized, revealing that both sources induced significant alterations in surface composition and crystal structure. These interactions result in a more uniform chemical composition, reduced surface roughness, and a shift from an amorphous phase to a nanocrystalline or amorphous-nanocrystalline state. The results underscore the potential of high-energy sources for efficient surface engineering, offering opportunities for customized material surface modifications through meticulous adjustment of these generation parameters.
Small sized of anion doping effect on semiconducting single-walled carbon nanotube network for field-effect transistors
Authors: Yang Dongseong , Moon Yina , Han Nara , Lee Minwoo , Beak Jeongwoo , Song Geon Chang , Lee Seung-Hoon , Kim Dong-Yu
Published: July 2024

Carbon nanotubes have shown great promise for high-performance, large-area, solution processable field-effect transistors due to their exceptional charge transport properties. In this study, we utilize the spin-coating method to form networks from selectively sorted semiconducting single-walled carbon nanotubes (s-SWNTs), aiming for scalable electronic device fabrication. The one-dimensional nature of s-SWNTs, however, introduces significant roughness and charge trap sites, hindering charge transport due to the van der Waals gap (∼0.32 nm) between nanotubes. Addressing this, we explored the effects of anion doping on the spin-coated s-SWNT random network, with a focus on the influence of the small size of halogen anions (0.13–0.22 nm) on these electronic properties. Raman and ultraviolet–visible–near-infrared optical spectroscopy results indicate that smaller anions significantly enhance doping effects through strong non-covalent anion–π interactions, improving charge transport and carrier injection efficiency in s-SWNTs, especially for n-type operation. This improvement is inversely proportional to the size of the halogen anions, with the smallest anion (fluorine) effectively transitioning the electrical characteristics of the s-SWNT network from ambipolar to n-type by reducing both junction and contact resistances through anion doping, based on anion–π interaction.
Charge transfer plasmons in nanoparticle arrays on graphene: Theoretical development
Authors: Fedorov A. S. , Eremkin E. V.
Published: July 2024

The properties of charge transfer plasmons (CTPs) in periodic metallic nanoparticle arrays (PMNPAs) on the single-layer graphene surface are studied within a computationally efficient original hybrid quantum-classical model. The model is based on the proven assumption that the carrier charge density in doped graphene remains unchanged under plasmon oscillations. Calculated CTP frequencies for two PMNPA geometries are shown to lie within the THz range and to be factorized, i.e., presented as a product of two independent factors determined by the graphene charge density and the PMNPA geometry. Equations are derived for describing the CTP frequencies and eigenvectors, i.e., oscillating nanoparticle charge values. It is shown that the CTP plasmons having a band structure containing a wave vector and a band number, like to phonons in periodic media, can be divided into an acoustic mode and optical CTP modes. For the acoustic modes, the CTP group velocity tends to zero at k→0, but reaches a value of ∼VFermi in graphene inside the Brillouin zone, while for the optical modes, the group velocity dispersion is extremely weak, although their energy is higher than the acoustic plasmon energies. It is shown that the calculated dependence of CTP frequencies on the carrier concentration in graphene is in good agreement with experimental data. We believe that the proposed model can help in designing various graphene-based terahertz nanoplasmonic devices of complex geometry due to very high computational efficiency.
Multilevel magnetoresistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 heterostructure grown on MgO
Authors: Khanas Anton , Hebert Christian , Hrabovsky David , Becerra Loïc , Jedrecy Nathalie
Published: July 2024

Magnetic tunnel junction (MTJ) is one of the cornerstones of modern information technologies. Bringing MTJ's operation beyond the conventional binary regime, enabled by tunneling magnetoresistance (TMR) effect, is highly promising for prospective memory technologies and neuromorphic hardware development. In this paper, we demonstrate multilevel magnetoresistance states in an all-perovskite-oxide La0.7Sr0.3MnO3 (LSMO)/BaTiO3/LSMO heterostructure grown on MgO substrates. Unlike traditional TMR, we observe four distinct regions of increased magnetoresistance, which result in three magnetic field-induced resistance states in total. We show that the observed phenomenon arises from the low-field magnetoresistance effect, which occurs in the two epitaxial LSMO layers, independently and at different values of the magnetic field. The effect is well simulated by a model based on the presence of structural defects and non-uniform deformations in the LSMO layers, induced by the large lattice mismatch of the LSMO with the MgO substrate. We believe that our findings contribute to the understanding of complex magnetoresistance effects in MTJs and can be taken into consideration for the design of multi-bit memory cells or neuromorphic devices.
Photon emission and radiation reaction effects in surface plasma waves in ultra-high intensities
Authors: Kleij P. S. , Marini S. , Caetano de Sousa M. , Grech M. , Riconda C. , Raynaud M.
Published: July 2024

Manipulating and harnessing plasmonic phenomena in the ultra-relativistic regime reveal promising prospects for the use of surface plasma waves (SPW) to create high-energy particle and radiation sources in the next generation of multi-petawatt lasers. Indeed, relativistic high-charge electron bunches can be produced by SPW excited by ultra-high intensity femtosecond lasers impinging on a periodically modulated solid-density target. In this regime, there is good evidence that SPW excitation survives and that the produced electron bunches experience strong acceleration, thus emitting large amounts of electromagnetic radiation. Therefore, extending the study to ultra-high laser intensities (I>1021 W/cm2), the use of a resonant grating for SPW generation represents an interesting alternative to light sources, as the energy lost by electrons due to radiation emission is transferred to high-energy γ photons. In addition, we show that using a laser with wavefront rotation coupled with a tailored blazed grating improves photon emission in the ultra-relativistic regime of interaction.
Fast, universal scheme for calibrating microwave crosstalk in superconducting circuits
Authors: Yang Xiao-Yan , Zhang Hai-Feng , Du Lei , Tao Hao-Ran , Guo Liang-Liang , Wang Tian-Le , Jia Zhi-Long , Kong Wei-Cheng , Chen Zhao-Yun , Duan Peng , Guo Guo-Ping
Published: July 2024

A challenge in building large-scale superconducting quantum processors is the precise control and manipulation of the qubit state. However, the crosstalk between the microwave control lines impedes the parallel execution of high-fidelity digital and analog quantum operations. Here, we propose and demonstrate a universal compensation protocol for calibrating the microwave signal crosstalk. We also introduce amplified error sequences to optimize accuracy. Furthermore, we show a definitive improvement in parallel gate operations with crosstalk cancellation, demonstrating the technique's effectiveness. This work paves the way for superconducting hardware that features the automated calibration of microwave crosstalk, leading to enhanced fidelities in multiqubit circuits.
Significantly enhancing the through-plane thermal conductivity of epoxy dielectrics by constructing aramid nanofiber/boron nitride three-dimensional interconnected framework
Authors: Ren Jun-Wen , Zeng Rui-Chi , Yang Jun , Wang Zi , Wang Zhong , Zhao Li-Hua , Wang Guo-Long , Jia Shen-Li
Published: July 2024

Epoxy dielectrics with high through-plane thermal conductivity (λ) hold great promise for applications in the thermal management of advanced power electronics. Intensive attempts have been made to improve the λ of epoxy by filling with boron nitride nanosheets (BNNSs). However, it remains a great challenge to achieve a satisfactory increased λ by a small amount of BNNS loading. Herein, we reported a new strategy to prepare epoxy dielectrics with internal three-dimensional phonon transport channels by vacuum freeze-drying and vacuum impregnation. Aramid nanofibers (ANFs) and BNNSs were used for the collaborative construction of a vertical interconnected thermal framework. The resultant ANF-BNNS/epoxy achieved a high through-plane λ of 0.87 W m−1 K−1 at only 1.43 vol. % BNNS, which is ∼17.1% higher than that of the BNNS/epoxy counterpart with even 18.34 vol. % randomly distributed BNNS. The increasing efficiency of λ of epoxy by ANF-BNNS is tenfold more than that of the conventional blending methods. In addition, the ANF-BNNS/epoxy composite also exhibits a low dielectric constant and low dielectric loss. The findings of this study offer an inspired venue to develop high-performance thermally conductive epoxy dielectrics with a minimal BNNS loading.
Raman spectroscopy and photoluminescence study of PN junction p-graphene/n-GaAs
Authors: Souibgui M. , Ajlani H. , Cavanna A. , Madouri A. , Oueslati M. , Meftah A.
Published: July 2024

Single layer graphene (SLG) was synthesized via high-quality chemical vapor deposition (CVD) on high-quality copper and subsequently transferred onto SiO2 and on n-GaAs substrates with varying doping electron concentrations (n = 1016, 1017, 5 × 1017, 1018, and 5 × 1018 cm−3). The n-GaAs substrates were grown by molecular beam epitaxy. The optical properties of the SLG were investigated through photoluminescence (PL) and Raman spectroscopy measurements. Carrier concentration n or p and Fermi energy (EF) values in SLG were determined both before and after the transfer onto n-GaAs, and these findings were validated through PL studies. The Raman spectroscopy results indicated an increase in the transfer of electrons from n-GaAs to SLG as the doping electron density in n-GaAs increased. PL analysis revealed a significant change in the bandgap energy (Eg) of n-GaAs due to bandgap narrowing and the Burstein–Moss shift. Our data enable us to determine the energy band diagrams. Upon aligning the energy bands, an increase in transferred carrier density is accompanied by changes in Fermi energies and an increase in the potential barrier (∆U). The increase in ∆U is of significant interest to ensure that charges are directed more efficiently toward the cell’s electrical contacts in the case of photovoltaic application. There, they can contribute significantly to the generated electric current, thereby enhancing the performance of a cell. Our results can provide insights into the interaction in graphene-based heterostructures and aid in selecting the best parameters for developing new advanced devices.
Anomalously strong size effect on thermal conductivity of diamond microparticles
Authors: Wang Yufeng , Sun Bo
Published: July 2024

Diamond has the known highest thermal conductivity of around 2000 W m−1 K−1 and is, therefore, widely used for heat dissipation. In practical applications, synthetic diamond microparticles are usually assumed to have similar thermal conductivity to that of bulk diamond because the particle size is larger than the theoretical phonon mean free path, so that boundary scattering of heat-carrying phonons is absent. In this report, we find that the thermal conductivity of diamond microparticles anomalously depends on their sizes. The thermal conductivity of diamond microparticles increases from 400 to 2000 W m−1 K−1 with the size growing from 20 to 300 μm. We attribute the abnormally strong size effect to the long-range defects during the growth process based on analysis of point defects, dislocations, and thermal penetration depth dependence of thermal conductivity. Our results play a vital role in the design of diamond composites and in the improvement of the thermal conductivity of synthetic diamonds.
Cooperation in a non-ergodic world on a network - insurance and beyond
Authors: Wand Tobias , Kamps Oliver , Skjold Benjamin
Published: July 2024

Cooperation between individuals is emergent in all parts of society; yet, mechanistic reasons for this emergence are ill understood in the literature. A specific example of this is insurance. Recent work has, though, shown that assuming the risk individuals face is proportional to their wealth and optimizing the time average growth rate rather than the ensemble average results in a non-zero-sum game, where both parties benefit from cooperation through insurance contracts. In a recent paper, Peters and Skjold present a simple agent-based model and show how, over time, agents that enter into such cooperatives outperform agents that do not. Here, we extend this work by restricting the possible connections between agents via a lattice network. Under these restrictions, we still find that all agents profit from cooperating through insurance. We, though, further find that clusters of poor and rich agents emerge endogenously on the two-dimensional map and that wealth inequalities persist for a long duration, consistent with the phenomenon known as the poverty trap. By tuning the parameters that control the risk levels, we simulate both highly advantageous and extremely risky gambles and show that despite the qualitative shift in the type of risk, the findings are consistent.
Effective optimization of atomic decoration in giant and superstructurally ordered crystals with machine learning
Authors: Cerasoli Frank T. , Donadio Davide
Published: July 2024

Crystals with complicated geometry are often observed with mixed chemical occupancy among Wyckoff sites, presenting a unique challenge for accurate atomic modeling. Similar systems possessing exact occupancy on all the sites can exhibit superstructural ordering, dramatically inflating the unit cell size. In this work, a crystal graph convolutional neural network (CGCNN) is used to predict optimal atomic decorations on fixed crystalline geometries. This is achieved with a site permutation search (SPS) optimization algorithm based on Monte Carlo moves combined with simulated annealing and basin-hopping techniques. Our approach relies on the evidence that, for a given chemical composition, a CGCNN estimates the correct energetic ordering of different atomic decorations, as predicted by electronic structure calculations. This provides a suitable energy landscape that can be optimized according to site occupation, allowing the prediction of chemical decoration in crystals exhibiting mixed or disordered occupancy, or superstructural ordering. Verification of the procedure is carried out on several known compounds, including the superstructurally ordered clathrate compound Rb8Ga27Sb16 and vacancy-ordered perovskite Cs2SnI6, neither of which was previously seen during the neural network training. In addition, the critical temperature of an order–disorder phase transition in solid solution CuZn is probed with our SPS routines by sampling site configuration trajectories in the canonical ensemble. This strategy provides an accurate method for determining favorable decoration in complex crystals and analyzing site occupation at unprecedented speed and scale.
Impact of post-ion implantation annealing on Se-hyperdoped Ge
Authors: Liu Xiaolong , McKearney Patrick , Schäfer Sören , Radfar Behrad , Berencén Yonder , Kentsch Ulrich , Vähänissi Ville , Zhou Shengqiang , Kontermann Stefan , Savin Hele
Published: July 2024

Hyperdoped germanium (Ge) has demonstrated increased sub-bandgap absorption, offering potential applications in the short-wavelength-infrared spectrum (1.0–3.0 μm). This study employs ion implantation to introduce a high concentration of selenium (Se) into Ge and investigates the effects of post-implantation annealing techniques on the recovery of implantation damage and alterations in optical properties. We identify optimal conditions for two distinct annealing techniques: rapid thermal annealing (RTA) at a temperature of 650 °C and ultrafast laser heating (ULH) at a fluence of 6 mJ/cm2. The optimized ULH process outperforms the RTA method in preserving high doping profiles and achieving a fourfold increase in sub-bandgap absorption. However, RTA leads to regrowth of single crystalline Ge, while ULH most likely leads to polycrystalline Ge. The study offers valuable insights into the hyperdoping processes in Ge for the development of advanced optoelectronic devices.
Design and simulation of a wireframe DNA origami nanoactuator
Authors: Mogheiseh Maryam , Hasanzadeh Ghasemi Reza
Published: July 2024

This paper explores the use of deoxyribonucleic acid (DNA) origami structures as nanorobot components. Investigating the functional properties of DNA origami structures can facilitate the fabrication of DNA origami-based nanorobots. The wireframe structure stands out as one of the most interesting DNA origami structures. Hence, the present study aims to employ these structures to create DNA origami nanoactuators. The research delves into the design of DNA origami structures with the aim of opening under specific temperature conditions. Short DNA strands (staples) are one of the crucial parts of DNA origami structures, and the appropriate design of these strands can lead to the creation of structures with different properties. Thus, the components of the DNA origami nanoactuator are tailored to enable intentional opening at specific temperatures while maintaining stability at lower temperatures. This structural modification showcases the functional property of the DNA origami structure. The engineered DNA origami nanoactuator holds potential applications in medicine. By carrying drugs under specific temperature conditions and releasing them under different temperature conditions, it can serve as a platform for smart drug delivery purposes.
Simulation of a scintillator-based fast ion loss detector for steady-state operation in Wendelstein 7-X (invited)
Authors: LeViness A. , Lazerson S. A. , Jansen van Vuuren A. , Rueda-Rueda J. , Ayllon-Guerola J. , Bozhenkov S. , Corl D. , Ellis R. , Galdon-Quiroga J. , Garcia-Dominguez J. , Garcia-Munoz M. , Hidalgo-Salaverri J. , Ogawa K. , Pablant N. , Segado-Fernandez J. ,   W7-X Team
Published: July 2024

A quantitative theoretical framework has been created to model neutral beam injection and fast ion losses in the Wendelstein 7-X (W7-X) stellarator, including a novel method to develop synthetic diagnostics for fast ion loss detectors (FILDs) of many types, such as scintillating and Faraday Cup FILDs. This is the first time that this has been done in stellarator geometry with this level of fidelity, providing a way for fast ion losses to be predicted more precisely in future stellarator experiments and in W7-X. Simulations of the signal seen by a Faraday Cup FILD have been completed for multiple W7-X plasmas and show close agreement with the measured signals. This method is now applied to an actively water-cooled, scintillator-based FILD, which is currently in development to measure the fast ion loss distribution in W7-X in greater detail. The design makes use of a double slit to measure energy-and-pitch-angle-resolved losses of both co-going and counter-going fast ions. The diagnostic, which can be inserted to different radial positions, has been designed to withstand steady-state heat fluxes of up to 120 kW/m2 along with additional transient heat loads of 100 kW/m2 lasting for up to 20 s at a time. Simulations of W7-X standard magnetic configuration show up to 8 × 1013 (s−1 cm−2) ion fluxes onto the sensor from each neutral beam source and no signal from the counter-going slit. These simulations will help inform experimental proposals for future W7-X campaigns after installation of this diagnostic.
Crystallization and the liquid–liquid critical point in nonbonded modified-WAC models
Authors: Lascaris Erik , Marchese Francesca , Gaspar Nicole
Published: July 2024

For decades, it has been known that Liquid–Liquid Critical Points (LLCPs) can exist in one-component liquids, yet a comprehensive understanding of the conditions under which they arise remains elusive. To better comprehend the possible interplay between the LLCP and the crystalline phase, we conduct molecular dynamics simulations using the nonbonded family of modified-WAC (mWAC) models, which are known to exhibit a LLCP for certain parameter values. By comparing different versions of the mWAC model—those featuring a LLCP and those lacking one—we identify several key differences between the models relating to crystallization. Those models that do have a LLCP are found to have multiple stable crystalline phases, one of them being a solid-state ionic conductor similar to superionic ice. Moreover, we find that for models that do not have a LLCP, the liquid becomes a glass at a larger range of temperatures, possibly preventing the occurrence of a LLCP. Further studies are required to determine if these results are general or model-specific.
Full quantum calculations of the line shape for H2O perturbed by Ar at temperatures from 20 to 300 K
Authors: Chai Shijie , Yu Yipeng , Yang Dongzheng , Zhou Yanzi , Xie Daiqian
Published: July 2024

This work theoretically studied the spectral line shape of H2O perturbed by Ar in the temperature range of 20–300 K for the pure rotational lines below 360 cm−1, as well as three lines (31, 2 ← 44, 1, 54, 2 ← 41, 3, and 73, 5 ← 60, 6) in the v2 band. In order to perform precise dynamical calculations at low collision energies, a full-dimensional long-range potential energy surface was constructed for the H2O–Ar system for the first time to correct the long range of our newly developed intermolecular potential energy surface. Subsequently, the six line-shape parameters (pressure-broadening and -shifting parameters, their speed dependencies, and the complex Dicke parameters) were determined from the generalized spectroscopic cross section by the full quantum time-independent close-coupling approach on this new potential energy surface. Our theoretical results are in good agreement with the available experimental observations. Furthermore, the influence of the speed-dependence and Dicke narrowing effects on the line contour was revealed by comparing the differences among the Hartmann–Tran, quadratic-speed-dependent Voigt, and Voigt profiles. The temperature dependence of each line-shape parameter was further parameterized using the triplet-power-law for three pure rotational 61, 6 ← 52, 3, 41, 4 ← 32, 1, and 31, 3 ← 22, 0 lines. These line-shape parameters will provide a comprehensive set of theoretical references for subsequent experimental measurements.
Anisotropic growth of Au–Ag heteronanostructures through plasmon-induced reduction
Authors: Nishi Hiroyasu , Zuo Yuan , Kuroiwa Yoshinori , Tatsuma Tetsu
Published: July 2024

Plasmonic heteronanostructures are promising building blocks for photofunctional materials and devices including photocatalysts, optical materials, and optoelectronic devices. In the present work, we fabricated Au–Ag bimetallic heteronanostructures based on site-selective and anisotropic Ag deposition and growth on Au nanocubes. Plasmonic Au nanocubes were adsorbed onto a glass plate, and the distal mode or proximal–distal mode of the nanocubes was selectively excited in the presence of Ag+ and citrate ions. Polycrystalline Ag was deposited around the top of the Au nanocubes by the distal mode excitation, and single crystalline Ag was grown laterally from the Au nanocubes by the proximal–distal mode excitation. The present method would be applied to the fabrication of various plasmonic nanostructures composed of two or more heterodomains.
Cathode cooling effects on the neutron production rate in the glow discharge type of fusion neutron source
Authors: Sakabe Toshiro , Ishii Takaya , Mukai Keisuke , Yagi Juro
Published: July 2024

Fusion reactions on the cathode surface of glow discharge deuterium–deuterium fusion neutron sources contribute significantly to the neutron production rate (NPR). While the NPR shows a linear relationship with current in the low current regime, a rise in cathode temperature in the high-current regime causes stagnation of the NPR. This tendency may be caused by high-temperature-induced desorption of deuterium on the cathode. This study aims to clarify the relationship between NPR and deuterium desorption. The present study utilized a water-cooling system to prevent deuterium desorption on the cathode. A stainless-steel 304 cathode and a diamond-like carbon (DLC)-coated cathode were tested. The cooling system kept the cathode temperature below 315 K throughout the experiment. In the case of the DLC-coated cathode, the water-cooling system improves the NPR in a high-current regime (30 mA or more in the present study). At 50 kV and 60 mA, the NPRs were 1.87 × 106 and 8.39 × 105 (n/s), with and without water cooling, respectively. Furthermore, without the cooling system, the NPR correlation with the cathode temperature indicates good agreement with the estimation model of deuterium desorption on the DLC-coated cathode. This study demonstrates that suppression of deuterium desorption in the cathode improves NPR, especially in the high-current regime.
Experimental study of flow control on tip leakage flow in variable geometry linear turbine cascades with different pivot layouts
Authors: Liu Yueqi , Chen Shaowen , Zheng Longye , Xu Chen
Published: July 2024

Variable geometry turbines are essential for adjusting operational conditions in industrial gas turbines and variable cycle engines. These adjustments necessitate partial gaps at both ends of the variable guide vanes to alter the turning angle, consequently introducing an aerodynamic performance penalty. Moreover, the pivot layout profoundly influences aerodynamic losses. Research on turbine cascades that considers various partial gap layouts is limited, particularly in terms of experimental studies, which are rarely conducted. This study aims to diminish aerodynamic losses and augment the efficiency of gas turbines by examining the impact of pivot layouts on partial gap clearance and secondary flow. It further investigates the effectiveness of flow control strategies at the blade tip across different pivot configurations within a variable geometry turbine cascade, utilizing pneumatic probe scanning and surface oil flow visualization techniques. The results reveal that employing a cavity at the tip can significantly reduce aerodynamic losses in schemes both with and without a pivot, achieving maximum loss reductions of 15.8% and 3.7%, respectively. Additionally, a narrower squealer width can further decrease these losses. However, with a pivot located at the tip, the resulting separation flow and wake vortex become predominant sources of losses. The presence of the pivot weakens the tip leakage flow rate and the intensity of the tip leakage vortex (TLV), thus diminishing the effectiveness of cavity tip flow control. The cavity moderates TLV and enhances the interaction between TLV and the wake vortex, leading to increased aerodynamic losses.
On the higher-order smallest ring-star network of Chialvo neurons under diffusive couplings
Authors: Nair Anjana S. , Ghosh Indranil , Fatoyinbo Hammed O. , Muni Sishu S.
Published: July 2024

Network dynamical systems with higher-order interactions are a current trending topic, pervasive in many applied fields. However, our focus in this work is neurodynamics. We numerically study the dynamics of the smallest higher-order network of neurons arranged in a ring-star topology. The dynamics of each node in this network is governed by the Chialvo neuron map, and they interact via linear diffusive couplings. This model is perceived to imitate the nonlinear dynamical properties exhibited by a realistic nervous system where the neurons transfer information through multi-body interactions. We deploy the higher-order coupling strength as the primary bifurcation parameter. We start by analyzing our model using standard tools from dynamical systems theory: fixed point analysis, Jacobian matrix, and bifurcation patterns. We observe the coexistence of disparate chaotic attractors. We also observe an interesting route to chaos from a fixed point via period-doubling and the appearance of cyclic quasiperiodic closed invariant curves. Furthermore, we numerically observe the existence of codimension-1 bifurcation points: saddle-node, period-doubling, and Neimark–Sacker. We also qualitatively study the typical phase portraits of the system, and numerically quantify chaos and complexity using the 0–1 test and sample entropy measure, respectively. Finally, we study the synchronization behavior among the neurons using the cross correlation coefficient and the Kuramoto order parameter. We conjecture that unfolding these patterns and behaviors of the network model will help us identify different states of the nervous system, further aiding us in dealing with various neural diseases and nervous disorders.
Koopman neural operator approach to fast flow prediction of airfoil transonic buffet
Authors: Meng Deying , Zhu Yiding , Wang Jianchun , Shi Yipeng
Published: July 2024

Transonic buffet on airfoil is of great importance in the aerodynamic characteristics of aircraft. In the present work, a modified Koopman neural operator (KNO) is applied to predict flow fields during the transonic buffet process of the OAT15A [ONERA (National Office for Aerospace Studies and Research) Aerospatiale Transport aircraft 15 Airfoil] airfoil. Transonic buffet flow with different angles of attack is simulated by Reynolds averaged numerical simulation with the Menter's k−ω shear stress transport (SST) model at Reynolds number Re=3×106. A prediction model is directly constructed between the flow fields at several previous time nodes and that at the future time node by KNO. The predictions of flow fields with single sample and multi samples are performed to demonstrate the prediction accuracy and efficiency of KNO. The prediction of sequence flow fields based on the iterative prediction strategy is achieved for the transonic buffet process. The results indicate that KNO can achieve a fast and accurate prediction of flow physical quantities for the transonic buffet. Compared with other deep learning models including Unet and Fourier neural operator, KNO has a more advanced capability of predicting airfoil transonic buffet flow fields with higher accuracy and efficiency and less hardware requirements.
Experimental investigation on coupled-bunch instability and suppression for the upgrade of Beijing Electron–Positron Collider (BEPCII)
Authors: Su Jinliu , Liu Yudong , Liu Zhi , Yin Di , Lei Ge , Yue Junhui , Que Cunyang
Published: July 2024

After touching the design collision luminosity of 1.0 × 1033 cm−2 s−1 in 2016, this target has not been reached again for the upgrade of Beijing Electron–Positron Collider during physical collision operation in subsequent years due to various factors, such as the collision background, noise, and equipment stability under high power operation. One of the most serious factors was the beam instability, especially the coupled-bunch instability, whose sideband distribution was clearly displayed on the spectrum analyzer when the feedback system was OFF. Experimental measurements on coupled-bunch instability and the damping from the feedback system were carried out over the past two years. These measurements were conducted by transiently turning off/on the feedback system, and the bunch-by-bunch oscillations were recorded to obtain the mode distribution and growth and damping rates. The experimental results demonstrate that the feedback damping is strong enough to suppress instability, and precise adjustments to the feedback system during physical collision operation can increase the collision luminosity, which has been verified in last year’s physical run.
Using nested tensor train contracted basis functions with group theoretical techniques to compute (ro)-vibrational spectra of molecules with non-Abelian groups
Authors: Rey Michaël , Carrington Tucker
Published: July 2024

In this paper, we use nested tensor-train contractions to compute vibrational and ro-vibrational energy levels of molecules with five and six atoms. At each step, we fully exploit symmetry by using symmetry adapted basis functions obtained from an irreducible tensor method. Contracted basis functions are determined by diagonalizing reduced dimensional Hamiltonian matrices. The size of matrices of eigenvectors, used to account for coupling between groups of coordinates, is reduced by discarding rows and columns. The size of the matrices that must be diagonalized is thus substantially reduced, making it possible to use direct eigensolvers, even for molecules with five and six atoms. The symmetry-adapted contracted vibrational basis functions have been used to compute J = 0 energy levels of the CH3CN (C3v) and J > 0 levels of CH4.
Analysis of methane diffusion on permeability rebound and recovery in coal reservoirs: Implications for deep coalbed methane-enhanced extraction
Authors: Su Erlei , Zhu Xinyu , Chen Xiangjun , Zou Quanle , Yang Kang , Chen Haidong , Wei Jiaqi
Published: July 2024

A proper understanding of the effect of methane diffusion on coal reservoir permeability rebound and recovery is essential, as coal reservoir permeability is the key parameter influencing the efficiency of coalbed methane migration and computational research on it is lacking. In this paper, the multifield coupling model for methane migration was established. Then, two parameters, the influence coefficient of diffusion on permeability rebound (DPRB) and the influence coefficient of diffusion on permeability recovery (DPRC), were proposed to quantify the effect of methane diffusion on rebound and recovery of coal reservoir permeability. Subsequently, we used COMSOL software to study the variation rules of the coal reservoir permeability rebound time, permeability recovery time, and permeability rebound value, DPRB, and DPRC for different geologic parameters. The results shown that the permeability rebound time and recovery time are proportional to the coal seam initial pressure, but inversely proportional to the initial permeability and initial diffusion coefficient. The rebound value decreases with increasing coal seam initial pressure and initial permeability, but ascends with rising initial diffusion coefficient. DPRB declines with increasing coal seam initial pressure, initial permeability, and initial diffusion coefficient, but they are all greater than 0.7, indicating that methane diffusion has a significant effect on permeability rebound. The DPRC values for different coal seam initial pressures, initial permeabilities, and initial diffusion coefficients are above 0.98, which implies that methane diffusion dominates the permeability recovery process. Finally, a conceptual model was presented to research the mechanism of diffusion influence on rebound and recovery of coal reservoir permeability, and the implications for enhanced drainage of deep coalbed methane were discussed. Therefore, the results of this paper can provide a theoretical foundation for deep coalbed methane-enhanced extraction.
Coupled response of flow-induced vibration and flow-induced rotation of a circular cylinder with a triangular fairing
Authors: Zhu Hongjun , Hao Hongtao , Liu Bin , Li Yingmei
Published: July 2024

In this paper, a numerical simulation investigation is carried out on the coupled response of the flow-induced vibration (FIV) and flow-induced rotation (FIR) of a circular cylinder attached with a triangular fairing at a low Reynolds number of Re = 100. The primary focus is on the impact of FIR on FIV. The vibration response, hydrodynamic coefficient, vortex shedding mode, and flow field characteristics are examined for the fairings within the vibrational reduced velocity Ur range of 3–16 with shape angle of α = 45°, 60°, and 90°. The results reveal that at low Ur, all the three considered fairings have a good suppression effect on the FIV. Nevertheless, the galloping response emerges as Ur increases when α = 45° and 60°. In contrast, the vibration response of 90° fairing presents a wider lock-in region. The rotatable 2-degree of freedom (2-DoF) fairing has a better performance in the reduction of response amplitude and hydrodynamic coefficients. The 2S (two single vortices) vortex shedding mode mainly occurs in the vortex-induced vibration (VIV) region, while 2S–8S (from two to eight vortices), 2P (two pairs of vortices), 2T (two triplets of vortices), and P + T (a pair of vortices and a triple of vortices) modes emerge in the galloping branch. Moreover, four modes of wake structures are identified according to the variation of recirculation region and the migration of boundary layer separation point. Finally, the reduced regions of drag, lift, and amplitude are highlighted compared to the bare cylinder.
MMC: A Monte Carlo laboratory
Authors: Mezei Mihaly
Published: July 2024

This Note describes features of the program MMC, several of which are unique to MMC, developed over the past five decades. These include sampling in three different ensembles, biased moves, and some non-conventional analysis techniques.
Controllable electrical contact characteristics of graphene/Ga2X3 (X = S, Se) ferroelectric heterojunctions
Authors: Liu Xianghe , Mao Yuliang
Published: July 2024

Reducing the interface barrier between metals and semiconductors is crucial for designing high-performance optoelectronic devices based on van der Waals heterojunctions (HJs). This study proposes four models of HJs composed of graphene (GR) and Ga2X3 (X = S, Se) and systematically investigates their interface electronic properties, along with strain engineering and electric field effects. The results indicated that exploiting the interface dipole-induced potential step allows modulation of the Schottky barrier height (SBH) and contact type of the HJs by altering the contact interfaces. In the BGR/Ga2S3 HJs (BGR means GR positioned at the bottom of Ga2X3), only a small positive (negative) electric field is required to realize the transition from n-type Schottky to p-type Schottky (Ohmic) contacts. Also, strain engineering provides additional means for flexible and controllable contact types, facilitating the design of reversible logic circuits. It indicates the physical insights and strategic interventions of GR/Ga2X3 HJs tunable SBH and offers theoretical guidance for the design of two-dimensional ferroelectric nanodevices with high-quality electrical contact interfaces.
Hybrid improper ferroelectricity in La2Sr (Sc1−xFex)2O7 ceramics with double-layered Ruddlesden–Popper structures
Authors: Guo Zhe , Zhang Zheng Duan , Liu Xiao Qiang , Chen Xiang Ming
Published: July 2024

Numerous hybrid improper ferroelectrics have been discovered in bulk oxides with layered perovskite structures. In contrast, the competition between the interlayer rumpling and oxygen octahedral rotation suppresses the ferroelectricity in layered perovskite material with trivalent cation at the B-site. In the present work, single-phase dense La2Sr(Sc1−xFex)2O7 ceramics with double-layered Ruddlesden–Popper structures have been prepared, and room-temperature ferroelectricity is discovered in the ceramics with x ≤ 0.10. The ferroelectric polarization and coercive field decrease with increasing content of Fe3+ cations, consistent with the decline of oxygen octahedral rotation and tilting angles. Although the linear relationship between the Curie temperature and the tolerance factor for La2Sr(Sc1−xFex)2O7 ceramics is established, the line is far away from that for A2+3B4+2O7 ceramics due to the large interlayer rumpling in the present ceramics. Although no single-phase multiferroic has been discovered in this work, an effective way to introduce magnetism into hybrid improper ferroelectric is provided.
Are we missing opportunities to detect acute rheumatic fever and rheumatic heart disease in hospital care? A multijurisdictional cohort study
Authors: Woods John A. , Sodhi-Berry Nita , MacDonald Bradley R. , Ralph Anna P. , Francia Carl , Stacey Ingrid , Katzenellenbogen Judith M.
Published: July 2024

Objective This study aimed to investigate potential missed diagnoses of acute rheumatic fever and rheumatic heart disease during hospital-based care among persons subsequently identified with these conditions. Methods This retrospective cohort study used linked emergency department and inpatient administrative records from Queensland, Northern Territory, South Australia, and New South Wales during 2003–2018 (varying between jurisdictions by completeness of data) of all persons first identified with acute rheumatic fever or rheumatic heart disease while aged 8–24 years. Using coded discharge diagnoses from the preceding 3 years, we identified presentations (e.g. joint pains or heart murmur without specific identified cause) that potentially mimic and thereby represent a missed opportunity to detect acute rheumatic fever or rheumatic heart disease. Sociodemographic factors associated with experiencing ≥1 mimic diagnoses were investigated using multivariable logistic regression models. Results Among 1855 persons, 65 (3.5%) (using narrow diagnostic inclusions) and 146 (7.9%) (with broad inclusions) experienced ≥1 mimic diagnosis. Joint disorders predominated. Mimics categorised as ‘high-likelihood’ (most specific) were more frequent among persons subsequently diagnosed as young adults (18–24 years) than as children (8–12 years) (odds ratio [OR] 2.45, 95% confidence interval [CI] 1.34–4.47), and those from low-risk ethnic groups (including Australian-born non-Indigenous persons) compared with Aboriginal and Torres Strait Islander peoples (OR 2.44, 95% CI 1.02–5.85). Conclusion Missed opportunities to detect acute rheumatic fever and rheumatic heart disease continue to occur in Australian hospitals, and present disproportionately among persons from demographic groups considered to be at low risk, suggesting the need for enhanced clinical suspicion in these groups.
In the light of small things
Authors: Czyzewski Krzysztof
Published: July 2024

What is the connection between Jeff Goldfarb and myself that began many years ago when he visited my small town of Sejny in Poland? From the very beginning when we met, the feeling was that we had known one another for a long time because there was a kind of brotherhood. What was behind that encounter? What was the power of this encounter between us? And what happened at the kitchen table that once existed in communist Poland in the 1970s and 1980s when Jeff visited us in our country? What happened to this kitchen table after 1989? Where is it today? Where is this table?
Small things, deep resonance: A sociology for dark times
Authors: Goldfarb Jeffrey C.
Published: July 2024

Jeffrey C Goldfarb responds to the commentaries and reflections of the authors in this volume.
Democratisation without democracy: Musical discourse in the digital age
Authors: Hanrahan Nancy Weiss
Published: July 2024

The contemporary discourse of digitalisation suggests that the music world has been ‘democratised’ through technical protocols that allow for greater access and voice, and eliminate the need for intermediaries such as record company executives and professional music critics. Yet there is little engagement in this formulation with normative conceptions of democracy. Indeed, the formal similarities between technological platforms and democratic structures obscure what are far more significant substantive differences. Using examples of historical moments when the connection between music and normative conceptions of democracy in the US were significantly more robust, I consider developments that led to the hollowing out of such critical public discourse about music and analyse the transposition of meaning of key democratic terms. This work builds on Jeffrey Goldfarb's commitment to the relative autonomy of the arts and sciences and their central place in democratic public life.
The Power of fiction and a shared framework in confronting contested pasts
Authors: Gutman Yifat
Published: July 2024

Artistic memorial interventions that raise the question ‘what if?’ – what life in the present would look like had past events unfolded differently – can be understood in light of the concept ‘as if’ in Jeffrey Goldfarb’s Politics of Small Things. ‘As if’ constitutes a shared framework for public debate that enables a more equal voice to participants with different identities and social positions who meet ‘as if’ they were equal. In cases of conflict over the past and present, like Nakba’s memory in Israel–Palestine, the creation of a joint framework in which all sides can participate without erasing asymmetrical violence and power relations is crucial yet difficult. By opening up space for the consideration of counter histories, a new public can be formed, even if temporarily, and potentially expand the horizon of public debate.