bluuebunny/crossref_metadata_2025 huggingface dataset:
Obscured star clusters in the inner Milky Way
Authors: Gupta Akash , Ivanov Valentin D. , Preibisch Thomas , Minniti Dante
Published: November 2024

Context. Milky Way star clusters provide important clues about the history of star formation in our Galaxy. However, the dust in the disk and in the innermost regions hides them from the observers.

Aims. Our goal is twofold. First, to detect new clusters – we have applied the newest methods of detecting clusters with the best available wide-field sky surveys in the mid-infrared because they are the least affected by extinction. Second, we address the question of cluster detection’s completeness, for now limiting it to the most massive star clusters.

Methods. This search is based on the mid-infrared Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), to minimize the effect of dust extinction. The search Ordering Points To Identify the Clustering Structure (OPTICS) clustering algorithm was applied to identify clusters, after excluding the bluest, presumably foreground sources, to improve the cluster-to-field contrast. The success rate for cluster identification was estimated with a semi-empirical simulation that adds clusters, based on the real objects, to the point source catalog, to be recovered later with the same search algorithm that was used in the search for new cluster candidates. As a first step, this was limited to the most massive star clusters with a total mass of ~104 M⊙.

Results. Our automated search, combined with inspection of the color-magnitude diagrams and images, yielded 659 cluster candidates; 106 of these appear to have been previously identified, suggesting that a large hidden population of star clusters still exists in the inner Milky Way. However, the search for the simulated supermassive clusters achieves a recovery rate of 70–95%, depending on the distance and extinction toward them.

Conclusions. The new candidates – if confirmed – indicate that the Milky Way still harbors a sizeable population of unknown clusters. However, they must be objects of modest richness, because our simulation indicates that there is no substantial hidden population of supermassive clusters in the central region of our Galaxy.
Femmes oasiennes au Maroc : actrices de la survie des oasis
Authors: Bossenbroek Lisa , Ftouhi Hind , Berger Elisabeth , Kadiri Zakaria
Published: November 2024

Les régions oasiennes du Maroc sont confrontées à des changements continus liés à des facteurs comme la rareté de l’eau, les migrations et l’urbanisation, conditionnant la survie de ces espaces millénaires. Cependant, les activités des femmes et leurs contributions sociales et économiques face à ces changements sont peu prises en compte dans le monde académique et par les politiques publiques. La question qui se pose est en particulier de savoir comment les femmes vivent ces changements et de quelle manière elles y contribuent. Pour y répondre, nous nous appuyons sur une étude ethnographique menée entre 2019 et 2023 dans les oasis du sud-est du Maroc (vallées du Drâa et du Todgha). Les résultats soulignent le rôle continu joué par les femmes oasiennes dans la survie d’un espace confronté à la rareté de l’eau. Alors que leurs activités quotidiennes sont bouleversées, elles se lancent dans des activités économiques et sociales tout en cherchant à répondre à leurs aspirations, désirs et besoins. À travers de nouveaux services liés aux secteurs agricole et non agricole, comme les boutiques de beauté, les coopératives et les activités sportives, les femmes oasiennes renouvellent l’espace oasien et le diversifient. Chemin faisant, elles se forgent de nouvelles identités féminines comme commerçante, présidente, membre d’organisation collective, agricultrice, ou encore créatrice, qu’elles cherchent à combiner avec leur identité de mère, d’épouse, de fille, de femme rurale, en négociant les rapports sociaux genrés. Notre analyse permet de décentrer le rôle de l’agriculture dans les dynamiques rurales et de dévoiler d’autres tendances et domaines qui jouent un rôle tout aussi important dans le développement rural, mais elle illustre en même temps la fragilité de ces nouvelles activités et la difficulté de d’élaborer de nouvelles identités féminines rurales.
The exploration of the gamma-ray sky with the CTAO
Authors: Miener Tjark , Montaruli Teresa ,   The CTAO Consortium
Published: November 2024

The Cherenkov Telescope Array Observatory (CTAO) represent the next generation of gamma-ray astronomy research infrastructures. Among the messengers from the highest energy universe, gamma rays have the highest event rates, hence they play a key role in the multi-messenger approach involving neutrino and gravitational wave probes, which on the other hand propagate without attenuation.
JWST and lensing galaxy clusters: reaching for galaxies in the early universe
Authors: Iani Edoardo
Published: November 2024

How did galaxies form? How have they evolved over cosmic time? These are two central questions that astronomers have investigated now for decades through extragalactic studies. While the existence of galaxies beyond the Milky Way was recognised nearly a century ago, it was not until the 1990s with the launch of the Hubble Space Telescope (HST) that astronomers were able to systematically study distant galaxies and explore their properties and evolutionary histories.
An investigation on the mechanical and corrosion characteristics of magnesium-zinc alloy nanocomposites manufactured via ultrasound-assisted stir squeeze casting
Authors: Naveen Srinivas Madugula , Krishnan Parthiban , Selvam Veerappan , Veeranjaneyulu Itha , Srinivasa Rao Nidamanuri , Peyyala Anusha , Sateesh Nagari , Subbiah Ram
Published: November 2024

Magnesium alloy (Mg-Zn) was strengthened by including silicon carbide nanoparticles at different weight rates (0, 0.5, 1.0, and 1.5 wt%). The fabrication process involved the help of ultrasonication-assisted stir squeeze casting method. We studied the mechanical, microstructural, and corrosion quality of nanocomposites in relation to variations in SiC particle weight percentage and grain size. A comparison was made between the experimental results and the basic alloy. The findings show that nanocomposites’ mechanical characteristics improve as the SiC particle concentration rises and falls as the particle size increases. In accordance with the ASTM standard, immersion and potentiodynamic polarization tests were conducted to validate that the nanocomposites’ resistance to corrosion increased as the reinforcement weight percentage was increased. The optical microscope was used to observe the grain size. Nanoparticles are evenly distributed throughout the Mg matrix, as shown in scanning electron micrographs. XRD confirms that the nanocomposites include SiC. The nanocomposite reinforced with 1.5 wt% SiCP had 44% higher microhardness and 38% higher tensile strength than the base alloy.
Medium-scale traveling ionospheric disturbances created by primary gravity waves generated by a winter storm
Authors: Kogure Masaru , Chou Min-Yang , Yue Jia , Otsuka Yuichi , Liu Huixin , Sassi Fabrizio , Pedatella Nicholas , Randall Cora E. , Harvey V. Lynn
Published: November 2024

This study explores the meteorological source and vertical propagation of gravity waves (GWs) that drive daytime traveling ionospheric disturbances (TIDs), using the specified dynamics version of the SD-WACCM-X (Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension) and the SAMI3 (Sami3 is Also a Model of the Ionosphere) simulations driven by SD-WACCM-X neutral wind and composition. A cold weather front moved over the northern-central USA (90–100°W, 35–45°N) during the daytime of 20 October 2020, with strong upward airflow. GWs with ~500–700 km horizontal wavelengths propagated southward and northward in the thermosphere over the north-central USA. Also, the perturbations were coherent from the surface to the thermosphere; therefore, the GWs were likely generated by vertical acceleration associated with the cold front over Minnesota and South Dakota. The convectively generated GWs had almost infinite vertical wavelength below ~100 km due to being evanescent. This implies that the GWs tunneled through their evanescent region in the middle atmosphere (where a squared vertical wavenumber is equal to or smaller than 0) and became freely propagating in the thermosphere and ionosphere. Medium-scale TIDs (MSTIDs) also propagated southward with the GWs, suggesting that the convectively generated GWs created MSTIDs.
A New Predisposing Factor for Postoperative Atrial Fibrillation: Tube Insertion Site
Authors: Apaydın Zinar , Timur Barış , Yazıcı Batuhan , Gözaçık Kübra , Akbaş Anıl , Aksu Timuçin , İyigün Taner
Published: November 2024

Background The aim of this study is to compare the insertion sites of drainage tubes placed in the left thorax after elective coronary artery bypass grafting (CABG) surgeries.

Materials and Methods Patients were divided into two groups based on the site of tube insertion into the left hemithorax: those with a tube inserted from the subxiphoid region and those with a tube inserted from the left intercostal region. Comparative analyses between these two groups and factor analyses contributing to the outcome were performed.

Results There were no significant differences observed in terms of age, gender, height, and weight among patients undergoing coronary artery bypass surgery based on the site of drain placement. Twelve patients (5.2%) required re-drainage procedures, with five (41.7%) for pneumothorax and seven (58.3%) for pleural effusion. Atelectasis was absent in 144 patients (62.1%) while present in 88 patients (37.9%). The frequency of atrial fibrillation (AF) was significantly higher in the group with intercostal drains. Additionally, pain scale scores were significantly higher in patients with intercostal drains. Path analysis revealed that the visual pain scale value played a full mediating role in the effect of the drain site on AF.

Conclusion The statistically significant occurrence of pain and higher rates of postoperative AF in patients with intercostal tube placement are noteworthy. We believe that in patients undergoing elective coronary artery bypass surgery, the drain placed in the left hemithorax should be inserted from the subxiphoid region, if there are no contraindications.
High-resolution Ultrasound of Peripheral Nerve Disorders
Authors: Le Corroller Thomas
Published: November 2024

Peripheral nerve disorders refer to any condition that damages the peripheral nervous system with variable presentations and numerous causes. The diagnosis is usually suspected clinically and then confirmed using electrophysiology. Yet electrodiagnostic studies lack precise anatomical delineation and often cannot determine the underlying cause of the peripheral neuropathy. However, thanks to recent technological advances, high-resolution ultrasound (HRUS) and magnetic resonance (MR) imaging have emerged as exceptional modalities to identify the exact site of pathology and demonstrate the underlying etiology. These developments have led to a multimodality approach to peripheral nerve disorders. Imaging provides anatomical and morphological information while functional evaluation remains derived from electrodiagnostic study. This article reviews the HRUS features of common as well as less frequent peripheral nerve disorders: entrapment neuropathies, traumatic injuries, neuralgic amyotrophy, polyneuropathies, and nerve tumors.
Proximal Femoral Intraosseous Schwannoma
Authors: Shah Risha , Baker Jonathan C. , Malik Mariam A. , Northrup Benjamin E.
Published: November 2024

Intraosseous schwannoma is a rare benign nerve sheath tumor comprising < 1% of bone tumors. Relatively common locations for this tumor include the skull and mandible, and, to a lesser degree, the spine and sacrum. Intraosseous schwannoma involving the appendicular skeleton is exceedingly rare. The clinical and imaging presentation, as in this case, is nonspecific and includes pain in the setting of a lytic bone lesion. The first step in management is bone biopsy that often produces greater than expected pain. Definitive management is surgical.
Detection of antiferromagnetic order in a RuO2/Pt bilayer by spin Hall magnetoresistance
Authors: Kobayashi Yuta , Karube Shutaro , Sugiura Itaru , Narita Hideki , Hisatomi Ryusuke , Shiota Yoichi , Ono Teruo
Published: November 2024

Altermagnets have spin-split band structures that correspond to the rotational symmetry of the two sublattices in real space. Theoretically, their unique band structures are expected to exhibit intriguing transport phenomena, depending on their magnetic structures. Anomalous Hall effect (AHE) measurement is a method by which to electrically detect magnetic structure and has been reported for typical altermagnets, such as RuO2 and MnTe. However, AHE measurements are limited to specific cases. Thus, it is important to apply other methods by which to determine functionality based on magnetic structure. In this study, we report the spin Hall magnetoresistance (SMR) in a RuO2 (1 nm)/Pt (10 nm) system. A negative SMR signal is clearly observed, indicating the spin-flop antiferromagnetic structure of RuO2. Interestingly, a negative SMR was observed, even at 1 T, which is much smaller than the estimated spin-flop field reported in a previous study. This reflects the thinner film of RuO2 in our study, suggesting that thickness control is effective in adjusting the magnetic anisotropy of RuO2. In addition, the temperature-dependent SMR measurement revealed the Néel temperature of 1 nm thick RuO2 to be 70 ± 9 K. Our results show that SMR measurement can serve as an efficient tool to explore the magnetic features in an altermagnet.
Atomic layer deposition of ultrathin nitride films for enhanced carrier lifetimes and photoluminescence in CdTe/MgCdTe double heterostructures
Authors: Abbasi Haris Naeem , Qi Xin , Ju Zheng , Ma Zhenqiang , Zhang Yong-Hang
Published: November 2024

This work evaluates the passivation effectiveness of ultrathin nitride layers (SiNx, AlN, and TiN) deposited via atomic layer deposition on CdTe/MgCdTe double heterostructures for solar cell applications. Time-resolved photoluminescence and photoluminescence measurements revealed enhanced carrier lifetimes and reduced surface recombination, indicating improved passivation effectiveness. These results underscore the potential of SiNx as a promising passivation material to improve the efficiency of CdTe solar cells.
Large magnetoresistance and high spin-transfer torque efficiency of Co2MnxFe1−xGe (0 ≤ x ≤ 1) Heusler alloy thin films obtained by high-throughput compositional optimization using combinatorially sputtered composition-gradient film
Authors: Barwal Vineet , Suto Hirofumi , Toyama Ryo , Simalaotao Kodchakorn , Sasaki Taisuke , Miura Yoshio , Sakuraba Yuya
Published: November 2024

Half-metallic ferromagnetic Heusler alloys having high spin polarization are promising candidates to realize large magnetoresistance (MR) ratio and high spin-transfer torque (STT) efficiency in next-generation spintronic devices. Since the Heusler alloy properties are sensitive to composition, optimizing the composition is crucial for enhancing device performance. Here, we report the fabrication of high-performance current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices using Co2MnxFe1−xGe (0 ≤ x ≤ 1) Heusler alloy, employing a high-throughput and detailed composition optimization method. The method combined composition-gradient films and local measurements to enable the composition variation from Co2FeGe to Co2MnGe to be efficiently studied on a single library sample with a small composition interval. The CPP-GMR devices fabricated from stacks annealed at 250 °C showed a clear composition dependence of MR with the maximum of MR ratio ∼38% in the Mn-rich region of x = 0.85. By increasing the annealing temperature to 350 °C, the MR ratio increased to ∼45% along with high STT efficiency ∼0.6 in the broad composition range of 0.2 ≤ x ≤ 0.7. The optimal composition for the highest MR changed with annealing temperature because of the stability of the GMR stack being higher in the lower x range. The record high MR for the all-metal CPP-GMR devices, at low annealing temperature of 250 °C was achieved by the detailed composition optimization. These results present the high potential of Co2MnxFe1−xGe and provide a comprehensive guidance on the composition optimization for achieving large MR ratio and high STT efficiency in the CPP-GMR devices.
Microfluidics for hydrodynamic investigations of sand dollar larvae
Authors: Chen Wesley A. , Lopez Bryant A. , Obenshain Haley B. , Villeda Moses M. , Le Brian T. , Ametepe Brenda A. A. B. , Lee Ariana M. , Pace Douglas A. , Ahrar Siavash
Published: November 2024

The life cycle of most marine invertebrates includes a planktonic larval stage before metamorphosis to bottom-dwelling adulthood. During the larval stage, ciliary-mediated activity enables feeding (capturing unicellular algae) and transporting materials (e.g., oxygen) required for the larva’s growth, development, and successful metamorphosis. Investigating the underlying hydrodynamics of the ciliary activities is valuable for addressing fundamental biological questions (e.g., phenotypic plasticity) and advancing engineering applications (e.g., biomimetic design). We combined microfluidics and fluorescence microscopy as a miniaturized particle image velocimetry approach to study ciliary-mediated hydrodynamics during suspension feeding in sand dollar larvae (Dendraster excentricus). First, feasibility was confirmed by examining the underlying hydrodynamics (ciliary-mediated vortex patterns) for low- and high-fed larvae. Next, ciliary hydrodynamics were tracked from 11 days post-fertilization (DPF) to 20 DPF for 21 low-fed larvae. Microfluidics enabled the examination of baseline activities (without external flow) and behaviors in the presence of environmental cues (external flow). A library of qualitative vortex patterns and quantitative hydrodynamics (velocity and vorticity profiles) was generated. Velocities were used to examine the role of ciliary activity in transporting materials. Given the laminar flow and the viscosity-dominated environments surrounding the larvae, overcoming the diffusive boundary layer is critical. Péclet number analysis for oxygen transport suggested that ciliary velocities help overcome the diffusion-dominated transport. The approach was used to examine the hydrodynamics of two additional marine larvae (P. helianthoides and S. purpuratus). Microfluidics provided a scalable and accessible approach for investigating the ciliary hydrodynamics of marine organisms.
Kinetic investigation of Kelvin–Helmholtz instability with nonequilibrium effects in a force field
Authors: Li Yaofeng , Lin Chuandong
Published: November 2024

The Kelvin–Helmholtz (KH) instability in a force field is simulated and investigated using a two-component discrete Boltzmann method. Both hydrodynamic and thermodynamic nonequilibrium effects in the evolution of KH instability are analyzed in two distinct states: interface roll-up and non-roll-up. It is interesting to note that there are critical thresholds for initial amplitude and Reynolds number, both of which are determined based on the vertical density gradient. Specifically, when the initial amplitude and Reynolds number exceed their respective critical thresholds, the interface undergoes roll-up. Conversely, if these parameters fall below their critical values, the interface fails to roll up. Moreover, the initial amplitude promotes the development of density gradients, mixing degree, mixing width, viscous stress tensor strength, and heat flux strength. In contrast, the Reynolds number enhances the evolution of density gradients but dampens the mixing degree, viscous stress tensor strength, and heat flux intensity. The effect of the Reynolds number on mixing width is analyzed as well.
Transferable performance of machine learning potentials across graphene–water systems of different sizes: Insights from numerical metrics and physical characteristics
Authors: Liu Dongfei , Wu Jianzhong , Lu Diannan
Published: November 2024

Machine learning potentials (MLPs) are promising for various chemical systems, but their complexity and lack of physical interpretability challenge their broad applicability. This study evaluates the transferability of the deep potential (DP) and neural equivariant interatomic potential (NequIP) models for graphene–water systems using numerical metrics and physical characteristics. We found that the data quality from density functional theory calculations significantly influences MLP predictive accuracy. Prediction errors in transferring systems reveal the particularities of quantum chemical calculations on the heterogeneous graphene–water systems. Even for supercells with non-planar graphene carbon atoms, k-point mesh is necessary to obtain accurate results. In contrast, gamma-point calculations are sufficiently accurate for water molecules. In addition, we performed molecular dynamics (MD) simulations using these two models and compared the physical features such as atomic density profiles, radial distribution functions, and self-diffusion coefficients. It was found that although the NequIP model has higher accuracy than the DP model, the differences in the above physical features between them were not significant. Considering the stochasticity and complexity inherent in simulations, as well as the statistical averaging of physical characteristics, this motivates us to explore the meaning of accurately predicting atomic force in aligning the physical characteristics evolved by MD simulations with the actual physical features.
Electric-field-induced polarization anisotropy of interband photoluminescence in GaAs
Authors: Shalygin V. A. , Makhov I. S. , Adamov R. B. , Vinnichenko M. Ya. , Khvostikov V. P. , Firsov D. A.
Published: November 2024

Near-infrared photoluminescence spectra of the n-doped gallium arsenide epilayer under heating lateral electric field conditions are studied. The field dependences of hot electron and hole temperatures are determined from photoluminescence spectra and from solving the power balance equation using current–voltage characteristic. Polarization anisotropy of the photoluminescence radiation arising due to the anisotropy of hot electron distribution function and angular dependence of the interband optical matrix element in the momentum space is observed and investigated. The obtained experimental data are in satisfactory agreement with the theoretical model.
Combustion characteristics of ammonia–air in a heat-recirculating Swiss-roll burner
Authors: Sun Bowen , Kang Xin , Wang Yu
Published: November 2024

Ammonia has emerged as a promising carbon-free fuel for mitigating greenhouse gas emissions. However, its application in practical combustion systems is limited by several issues including its low heating value and slow flame propagation speed, which have posed challenges in maintaining stable combustion. As an attempt to resolve these issues, we numerically investigated premixed ammonia–air combustion using a detailed chemical mechanism in a heat-recirculating, Swiss-roll burner that was proposed based on the concept of “excess-enthalpy.” The main focus was put on the flame stabilizations as well as characteristics of NO/N2O emissions across a wide range of operational conditions. The results showed that the use of the Swiss-roll burner led to a significantly broadened stability regime for pure ammonia combustion, which could be attributed to the effective preheating from combustion products to unburnt mixture. The relationship between the dimensionless heat transfer parameter and excess-enthalpy was quantified and a linear correlation was revealed. In addition, flow expansion and recirculation within the combustion chamber led to the generation of vortices, which was also beneficial for flame stabilizations. NO emissions at the burner outlet were witnessed to have a linear growth in the laminar flow region, a gentler increase in the flow-transition stage, and a final leveling off at the turbulent flow condition with the increase in Reynolds number. For a given Reynolds number, the NO emission showed a non-monotonic variation with equivalence ratios, with relatively low emission levels at either the fuel-lean or fuel-rich conditions. As another major concern, N2O emission was found more significant in the laminar flow region and at fuel-lean conditions, both of which should be avoided in practical operations.
Unsteady flow analysis in a pump as turbine impeller based on proper orthogonal decomposition and dynamic mode decomposition methods
Authors: Miao Senchun , Liu Leqi , Wang Xiaohui , Yang Junhu
Published: November 2024

Pump as turbine (PAT) is an efficient, simple, and cost-effective equipment combining pump and turbine and is one of the excellent energy recovery devices. It is helpful to master the flow characteristics of the key component impeller for the further optimization and design of the PAT. To analyze the unsteady flow features in the impeller of a double-suction pump operating as a turbine, numerical simulations were conducted using the shear stress transport (SST) k-ω turbulence model at the designed operating conditions. By utilizing proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods on the unsteady velocity field of a single cycle, the dominant modes up to the fourth order, along with their respective space–time information, can be extracted. The velocity field and vorticity field analysis were performed on the first four modes extracted using two different methods. Additionally, the vortex structures were extracted using the Ω method. The analysis demonstrates that the POD and DMD methods effectively decompose the intricate flow characteristics within the impeller into dynamic–static interference modes, fundamental modes, and dissipative modes. The dynamic–static interference mode is dominant, reflecting the flow characteristics influenced by the stationary components within the impeller. The vortex structure is mainly small tubular vortex and point vortex. The fundamental mode captures the steady flow field characteristics caused by the blade channel geometry. The vortex structure is mainly continuous tubular vortex and the diameter becomes larger. The dissipative mode reflects the flow separation generated on the blades by disturbances from the stationary components. The vortex structure is dominated by point vortex and discontinuous tubular vortex. Comparing the outcomes of the two modal analysis methods shows that the POD method has a distinct advantage in showcasing key changing nodes. In contrast, the DMD method is superior in isolating modes with a single frequency and in determining their stability.
Water invasion and residual gas distribution in partially filled fractures via phase-field method
Authors: Chu Haotian , Zhang Jicheng , Cao Youxun , Li Xuelong , Yu Haiyang , Li Faxin , Lu Jialin
Published: November 2024

Water invasion is a significant factor affecting the conductivity of fractures in coal seams. The partially contact characteristics of deep coal seam fractures are pronounced, and surface wettability varies significantly. However, there is a limited understanding of how water invasion behavior in partially filled fractures affects the gas produced by these fractures. In this study, a high-temperature and high-pressure contact angle testing device was employed to assess the wettability of coal seams under in situ conditions. The geometry of partially filled fractures was reconstructed using random functions, while the phase field method was employed to calculate the interactions at the two-phase interface during water invasion. The results indicate that the deep coal seams in the Ordos Basin demonstrate weak air-wetting properties under in situ conditions. The partially contact characteristics of the filled fractures in the deep coal seams categorize the fractures into distinct pore and throat regions. The variations in connectivity levels lead to the gas exhibiting uninvaded, clustered, and fully invaded characteristics following water invasion. The change in gas saturation during water invasion is more sensitive to larger values of lgCa and higher cos(θ). A larger displacement pressure difference and a smaller contact angle enable the invasion fluid to penetrate smaller throats, resulting in a higher number of clusters of residual gas and a smaller cluster radius. The results enhance our understanding of water invasion behavior, and the variability of fracture surface properties and gas-water two-phase flow in deep coal seams deserves further investigation.
Insights into flame flashback phenomenon utilizing a Strut-Cavity flame holder inside scramjet combustor
Authors: Pranaykumar Singeetham , Ghosh Amardip
Published: November 2024

Understanding upstream flame propagation in scramjets is challenging, particularly concerning flame flashback in a combustor with a novel strut-cavity flame holder. Two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed to investigate how Mach number and wall divergence affect flame behavior. The utility of the strut-cavity flame holder was highlighted through a study of its non-reacting flow characteristics. Flow dynamics are significantly altered as the shear layer above the cavity interacts with the downstream hydrogen jet. Shear layer dynamics and fuel-air mixing are improved through key factors such as shock-train behavior, cavity oscillations, and transverse fuel injection. The submerged fuel jet is less exposed to supersonic flow and demonstrates reduced entropy rise, achieving a 16% increase in mixing efficiency compared to standalone struts and a 46% improvement over transverse injection without a flame holder. Thermal choking shifts the shock train upstream, facilitating interactions with the shear layer and enhancing vortex formation, which decreases flow speed and promotes upstream flame propagation. The presence of OH radicals indicates that flame flashback follows a periodic pattern with an initial gradual slope, suggesting effective anchoring. Stability and flashback likelihood are affected by low-speed zones, vortex merging, and wall divergence. At Mach 3, combustion efficiency improves without wall divergence due to increased heat release, while wall divergence prevents flame flashback by sustaining supersonic core flow and managing flow-flame interactions. At higher core flow velocities, flame stabilization occurs at the cavity's separation corner, despite a tendency for upstream propagation, with validation of the URANS results achieved through two-dimensional large eddy simulations.
Enhanced energy storage performance in polyetherimide composites via oriented one-dimensional BZCT@BT core–shell filler
Authors: Feng Yu , Sun Jun , Zhang Zhonghua , Wang Puzhen , Zhang Wenchao , Yue Dong , Chen Qingguo
Published: November 2024

The development of dielectric capacitors toward high voltage and high power density requires materials with excellent insulation and energy storage performances. In this work, a polymer dielectric with polyetherimide (PEI) as the matrix and calcium barium zirconate titanate (BZCT) coated by barium titanate fiber (BT) as the filler (BZCT@BT) was constructed. The (0.5%–10% BZCT@BT/PEI) polymer dielectric has an excellent discharge energy density (Ue) of 6.66 J/cm3 and maintains an advanced charge/discharge efficiency (η) of 93.29% when the BT content was 0.5% and the BZCT particle content was 10%. The addition of BZCT endows the polymer dielectric with a higher relative dielectric constant (εr), while BT, maintaining a lower εr than BZCT, could reduce the electric field (E) distortion caused by the dielectric mismatch between PEI and BZCT. Oriented fiber fillers increase the breakdown strength of the polymer dielectric, ultimately increasing the performance of energy storage. A new strategy for the design of energy storage polymer dielectrics was provided by this work.
Wall-mounted circular cylinder flows
Authors: Liu Qiong
Published: November 2024

The flow over wall-mounted circular cylinders is influenced by variations in aspect ratio, Reynolds number, and boundary layer thickness, all of which affect the vortical structures in the wake. In this study, we conducted direct numerical simulations and data-driven techniques, including proper orthogonal decomposition (POD) and dynamic mode decomposition, to examine vortical flows behind wall-mounted circular cylinders with aspect ratios of 4, 8, and 12 at Reynolds numbers ranging from 60 to 800, based on cylinder diameter. The incoming boundary layer thickness varied from 0.05 to 0.25. Our findings reveal that a thicker boundary layer promotes the development of low-frequency symmetric vortical structures along the wall surface, suppressing antisymmetric wake shedding. Consequently, the induced upwashing motion of the flow behind the cylinder pushes the wake shedding region closer to the free-end side, facilitating quadrupole mean streamwise vortices. The wake shedding frequency is significantly altered as the symmetric low-frequency mode intensifies along the boundary. POD analysis demonstrates the coexistence of symmetric and antisymmetric vortical structures in the wake region. The presence of either antisymmetric or symmetric wake shedding is determined by the dominant frequency in the instantaneous flow. These findings substantiate previous conjectures about the simultaneous presence of symmetric and antisymmetric wake shedding modes and enhance our understanding of vortical flows around wall-mounted circular cylinders.
A flat-structured triboelectric nanogenerator based on PDMS/MXene for mechanical energy harvesting boxing training monitoring
Authors: Zhang Hui , Hao Qingwei , Liu Haishan
Published: November 2024

With the advancement of intelligent wearable sports monitoring devices, self-powered, flexible, and lightweight sensors have garnered significant attention. In this study, we propose a flat-structured triboelectric nanogenerator (PM-TENG) with multiple voids based on a PDMS/MXene film. The triboelectric layers consist of a PDMS/MXene film and a nylon film. When subjected to boxing impacts, the PM-TENG (size: 2 × 2 cm2) demonstrates remarkable performance, generating higher output. Our results show that the maximum open-circuit voltage (Voc) and short-circuit current density (Isc) of the PM-TENG reach 278 V and 8.46 µA/cm2, respectively. Additionally, when connected to a 40 MΩ load, the maximum output power of the PM-TENG can reach 4.44 mW/cm2. The PM-TENG effectively monitors various fundamental boxing techniques, including jabs, straight punches, and hook punches, thereby offering new opportunities for the development of smart sports technologies. This research underscores the potential of TENG applications in intelligent sports equipment, paving the way for future innovations in the field.
Study on the impact of hydraulic characteristics of new stilling pool in the context of energy conservation, emission reduction, and green construction
Authors: Tong Fei , Shi Shen'ao , Yang Jie , Li Gaochao , Bai Haohao , Cheng Lin
Published: November 2024

In the context of peaking carbon dioxide emissions and carbon neutrality, the construction of hydropower projects has strict regulations on the demand for construction materials, which also puts forward new requirements for design organizations. Several power stations have successfully applied spillway and floodway double-discharge building shared stilling pools as the new requirements of the design program. By the stilling pool, we mean it is an energy dissipation facility that generates a bottom-flow water jump downstream of the discharge structure. However, this type of program will be due to the uneven distribution of the flow of the double building problems, leading to its flow pattern being too complex and stilling pool dissipation characteristics being unclear. For this reason, based on the hydraulic model test method, this paper studies and analyzes the hydraulic characteristics of the new type of stilling pool in the shared stilling pool scheme of the double-drainage structure when the flood relief hole is needed to dominate the flow in particular circumstances. For the problems exposed during the test, three auxiliary dissipation schemes were added to the stilling pool, and their influence on the hydraulic characteristics of the stilling pool was studied. The results show that the baffle block can effectively reduce the stilling pool's bottom flow velocity and improve the stilling pool's water flow pattern compared with other programs. The dissipation effect is better than other schemes. The related research can provide technical support for further engineering applications of the double-drainage structure shared stilling pool program.
Is the mechanism of “fast sound” the same in liquids with long-range interactions and disparate mass metallic alloys?
Authors: Bryk Taras , Seitsonen Ari Paavo , Ruocco Giancarlo
Published: November 2024

We present ab initio simulations of a large system of 2400 particles of molten NaCl to investigate the behavior of collective mode dispersion beyond the hydrodynamic regime. In particular, we aim to explain the unusually strong increase in the apparent speed of sound with wave number, which significantly exceeds the typical positive sound dispersion of 10%–25% observed in simple liquids. We compare dispersions of “bare” acoustic and optic modes in NaCl with ab initio simulations of other ionic melts such as CuCl and LiBr, metallic liquid alloys such as Pb44Bi56 and Li4Tl, and the regular Lennard-Jones KrAr liquid simulated by classical molecular dynamics. Analytical expressions for the “bare” acoustic and optic branches of collective excitations help us to identify the impact of the high-frequency optic branch on the emergence of “fast sound” in binary melts. Our findings show that in ionic melts, the high-frequency speed of sound is much larger than in the simple Lennard-Jones liquids and metallic melts, leading to an observed strong viscoelastic increase in the apparent speed of sound—more than double its adiabatic value.
Current-induced resonance in long conductive ferromagnetic nano-wires
Authors: Alneari Mohammad H. , Aziz Mustafa M.
Published: November 2024

Ferromagnetic nanowires are receiving attention as functional elements in technologically important applications in microwave devices, spintronics, and biomedicine. They can be readily fabricated over large areas using electrodeposition, and their magnetic response can be tuned through control of their size, geometry, and composition. Additionally, their geometrical properties provide a stable spin structure for manipulating magnetization dynamics using spin-polarized currents for spintronic applications. Structural analysis of individual cobalt nanowires indicated magnetocrystalline anisotropy predominantly perpendicular to the nanowire axis. This significantly alters the micromagnetic energy landscape in the nanowire and breaks the circular symmetry of the dynamic magnetization and resonance modes which is often assumed in theory. In this article, we investigate, using finite-element micromagnetic–electromagnetic simulations, the effect of the variation of magnetocrystalline anisotropy angle on the dynamic magnetization in the nanowire and leads to a shift in the resonance frequencies and modes. The resonance is induced by a pulsed electric current applied along the nanowire axis and simulations include the contributions of magnetocrystalline anisotropy, exchange, dipolar fields, and eddy currents. Understanding the magnetization dynamics induced by electric currents and spin-wave modes in metallic magnetic nanowires and their size and anisotropy angle dependence is important for the design and tuning of magnetic nanowire arrays and devices.
Hydraulic characteristics of a deep tunnel system under different inflow conditions
Authors: Yu Chao , Yu Xiaodong , Zhang Jian , Wang Yiran , Xu Hui
Published: November 2024

Deep tunnel systems are characterized by large burial depths, long distances, and free-surface pressurized flows, operating under complex inflow conditions that can lead to strong pressure oscillations, particularly in the transitions between the main tunnel and shafts. This paper focuses on the deep tunnel system in Shanghai, China. A physical model was established based on the gravity similarity, and a corresponding one-dimensional mathematical model for free-surface and pressurized flows was established. The entire process of water inflow was observed in the experiment, and several inflow conditions, including different discharge and inflow schemes, were conducted to analyze the maximum pressure at the junction between shaft and deep tunnel, as well as the pressure along the tunnel. The deviation degree was introduced to validate the reliability of the numerical model. The impact of inflow distribution on deep tunnel pressure was studied with numerical simulation. The results indicated that simultaneous inflow from both shafts leads to a more pronounced phase difference. The pressure downstream after stabilization was higher than the pressure upstream. Simulations of pressure variations with the same discharge under different inflow scenarios revealed that symmetric inflow results in higher pressure at both the midpoint of the tunnel and in front of the downstream shaft. Asymmetric inflow only creates localized high pressure in front of the downstream shaft, with symmetric inflow producing greater pressure overall. When upslope inflow exceeds downslope inflow, it can also reduce the maximum pressure within the pipeline. The greater the difference in inflow on both sides, the smaller the pressure.
Boundary sources of velocity gradient tensor and its invariants
Authors: Chen Tao , Wu Jie-Zhi , Liu Tianshu , Salazar David M.
Published: November 2024

The present work elucidates the boundary behaviors of the velocity gradient tensor (A≡∇u) and its principal invariants (P, Q, R) for compressible flow interacting with a stationary rigid wall. First, it is found that the boundary value of A exhibits an inherent physical structure being compatible with the normal-nilpotent decomposition, where both the strain-rate and rotation-rate tensors contain the physical contributions from the spin component of the vorticity. Second, we derive the kinematic and dynamical forms of the boundary A flux from which the known boundary fluxes can be recovered by applying the symmetric–antisymmetric decomposition. Then, we obtain the explicit expression of the boundary Q flux as a result of the competition among the boundary fluxes of squared dilatation, enstrophy and squared strain-rate. Importantly, we find that both the coupling between the spin and surface pressure gradient, and the spin-curvature quadratic interaction (sw·K·sw), are not responsible for the generation of the boundary Q flux, although they contribute to both the boundary fluxes of enstrophy and squared strain-rate. Moreover, we prove that the boundary R flux must vanish on a stationary rigid wall. Finally, the boundary fluxes of the principal invariants of the strain-rate and rotation-rate tensors are also discussed. It is revealed that the boundary flux of the third invariant of the strain-rate tensor is proportional to the wall-normal derivative of the vortex stretching term (ω·D·ω), which serves as a source term accounting for the spatiotemporal evolution rate of the wall-normal enstrophy flux. As an example, several relevant surface quantities to the surface curvature are calculated based on global skin friction and surface pressure measurements in a flow over a National Advisory Committee for Aeronautics Fundamental Aeronautics Investigates The Hill model. These theoretical results provide a unified description of boundary vorticity and vortex dynamics, which could be valuable in understanding the formation mechanisms of complex near-wall coherent structures and the boundary sources of flow noise.
Two-molecule theory of polyethylene liquids
Authors: Li Huimin , Donley James P. , Wu David T. , Curro John G. , Tormey Caleb A.
Published: November 2024

Two-molecule theory refers to a class of microscopic, self-consistent field theories for the radial distribution function in classical molecular liquids. The version examined here can be considered as one of the very few formally derived closures to the reference interaction site model (RISM) equation. The theory is applied to polyethylene liquids, computing their equilibrium structural and thermodynamic properties at melt densities. The equation for the radial distribution function, which is represented as an average over the accessible states of two molecules in an external field that mimics the effects of the other molecules in the liquid, is computed by Monte Carlo simulation along with the intramolecular structure function. An improved direct sampling algorithm is utilized to speed the equilibration. Polyethylene chains of 24 and 66 united atom CH2 units are studied. The results are compared to full, many-chain molecular dynamics (MD) simulations and self-consistent polymer-RISM (PRISM) theory with the atomic Percus–Yevick (PY) closure under the same conditions. It is shown that the two-molecule theory produces results that are close to those of MD and is thus able to overcome defects of PRISM-PY theory and predict more accurate liquid structure at both short and long ranges. Predictions for the equation of state are also discussed.
Toward sustainable solar energy: Analyzing key parameters in photovoltaic systems
Authors: Gomidze Nugzar , Kalandadze Lali , Nakashide Omar , Jabnidze Izolda , Khajishvili Miranda , Shainidze Jaba
Published: November 2024

This study reviews recent advancements in solar energy technologies, focusing on enhancing the efficiency of photovoltaic systems. Key research areas include optimizing material properties, improving charge separation, and addressing sustainability challenges. This study identifies critical challenges in quantum dot solar cell technology, such as modeling spectral absorption, managing thermal losses, and evaluating long-term stability. Overall, these innovations represent significant strides toward more efficient and environmentally friendly solar energy solutions. This Review article offers a thorough investigation of the direct current parameters in photovoltaic panels, aiming to boost their efficiency and cost-effectiveness in production. This study underscores the importance of precise modeling and identification of solar cell parameters to more effectively harness solar energy, thereby underscoring its potential for enhancing energy capacity and environmental conservation. Our research includes experimental data on polycrystalline silicon solar cells and simulation results of both individual and polycrystalline cells conducted using the NI Multisim simulator. The focal points of this study encompass the efficient use of solar energy, the pivotal role of silicon as a semiconductor material, and novel methods for augmenting photovoltaic cell efficiency, such as employing nanowires and multilayer semiconductors. This Review Article also examines the effect of temperature on solar cell efficiency and addresses both the theoretical and practical measures of key photovoltaic parameters, including short-circuit current, open-circuit voltage, fill factor, and conversion efficiency.