bluuebunny/crossref_metadata_2025 huggingface dataset:
A horseshoe-shaped ring of diffuse emission detected at 1.4 GHz
Authors: Kumari Shobha , Pal Sabyasachi
Published: January 2024

We identify a horseshoe-shaped ring (HSR) of diffuse emission in J1407+0453 from the Faint Images of Radio Sky at Twenty-cm (FIRST) survey using the Very Large Array telescope at 1.4 GHz. An optical galaxy, SDSS J140709.01+045302.1, is present near the limb of the HSR of J1407+0453, with a spectroscopic redshift of z = 0.13360. The total extent of the source, including the diffuse emission of J1407+0453, is 65 arcsec (with a physical extent of 160 kpc), whereas the diameter of the HSR is approximately 10 arcsec (25 kpc). The flux density of the HSR is ∼47 mJy at 1400 MHz, whereas the flux densities of the whole diffuse emission of J1407+0453 at 1400 MHz and 150 MHz are 172 mJy and 763 mJy, respectively. We measure the radio luminosity of HSR J1407+0453 as 1.94 × 1024 W Hz−1, with a spectral index, α1501400 = −0.67. The black hole mass of J1407+0453 is 5.8 × 108 M⊙. We compare the HSR of diffuse emission of J1407+0453 with other discovered diffuse circular sources. The possible formation scenarios for J1407+0453 are discussed, so as to understand the nature of the source. We present a spectral index map of source J147+0453 to study the spectral properties of the source.
Cataclysmic variables and the disc instability model in the Gaia DR3 colour–magnitude diagram
Authors: Dubus Guillaume , Babusiaux Carine
Published: January 2024

Context. Cataclysmic variables (CVs) are semi-detached binaries composed of a white dwarf orbiting a lower-mass K or M star.

Aims. We investigate whether CVs are responsible for a new intriguing feature (the “hook”) that appears in the Gaia DR3 colour–magnitude Hertzsprung-Russell diagram (HRD) when selecting sources with low extinction. We also aim to understand the location of CVs in the HRD based on the predictions of the disc instability model (DIM). The DIM forms the foundation of our basic understanding of stable (novae-like) and outbursting CVs (dwarf novae).

Methods. We calculated the expected behaviour of CVs in the Gaia HRD while taking into account the variable light contributed by the accretion disc, the companion, the white dwarf, and the bright spot where the Roche lobe overflow stream from the companion intersects the disc.

Results. We find that the hook feature is most likely composed of CVs. The hook corresponds to the limited region where stable (novae-like) CVs must be located in the HRD according to the DIM. Unstable systems giving rise to dwarf novae outbursts trace counterclockwise loops in the HRD. The overall behaviour is consistent with the location of the various CV subtypes in the HRD.

Conclusions. These results can be used as a basis on which to pinpoint interesting outliers in the HRD, either due to their location or their tracks. These outliers could signal new subtypes, such as cold, stable CVs with truncated discs, or may challenge the disc instability model.
Modification of an N-Methyl Group toward a New Energetic Melt-Castable Material with a Good Energy-Stability Balance
Authors: Zhang Qinghua , Wang Yi , Chen Fang , Song Siwei
Published: January 2024

The energy and stability properties of energetic materials are often contradictory to each other (e.g., high energy vs low thermal stability). There is no doubt that it is still challenging to explore the effective balance between energetic performance and molecular stability, especially for melt-castable materials. In this study, we selected the 4-methoxy-3,5-dinitropyrazole framework and a stable nitro group to design a new energetic melt-castable compound, namely 4-methoxy-3,5-dinitro-1-(nitromethyl)-1H-pyrazole (MDNNMP). Compared with the N-methylation product DMDNP and the nitrato-substituted derivative MC-7, MDNNMP exhibits a better balanced performance, including good thermal stability (Td
: 203.7 °C), detonation velocity (Dv
: 8099 m s–1) and impact sensitivity (20 J). The favorable balanced performance of MDNNMP suggests that it is a suitable candidate as a high-performance melt-castable material. Additionally, compared with the nitratomethyl group, the nitromethyl group demonstrates superior advantages in performance regulation.
Catalytic Chain Transfer in Crosslinking Photopolymerizations
Authors: Worrell Brady T. , Bagnall Nicholas R. , Jones Meredith H. , Donovan Brian R.
Published: January 2024

Presented here is a detailed account of the development and implementation of macrocyclic cobaloxime complexes as sulfur-free, catalytic chain transfer agents (CTAs) in crosslinking photopolymerizations. Although much of this review is dedicated to understanding the fundamentals of catalytic chain transfer (CCT) in photopolymerizations, its impact on network topology and resultant mechanical properties, future goals of applying this technology to multimaterial 3D printing are also discussed. It is our long-term ambition for catalytic, sulfur-free CTAs to supplant existing consumptive, sulfur-based agents to provide new, unexplored, and not currently possible to fabricate photopolymeric materials with a specific eye towards application in dentistry, additive manufacturing, and responsive materials.

1 Introduction

2 History of Catalytic Chain Transfer (CCT)

3 Understanding Catalyst Purity and Chain Transfer Activity

4 Evidencing CCT in a Crosslinking Photopolymerization

5 Comparing Cobalt(II)-Catalysts to Other Relevant CTAs

6 Performance of Cobalt(II)-Catalysts in Commercial Resins

7 Limitations of Approach and Looking Forward
Palladium-Catalyzed Cycloisomerization of Carbamimidothioates
Authors: Kumazawa Hyu , Mizoguchi Kota , Nakada Masahisa , Okura Yoshifumi
Published: January 2024

A palladium-catalyzed cycloisomerization of carbamimidothioates with the formation of a quaternary carbon and a sulfide is described. The use of (IPr)Pd(allyl)Cl (CX21), K3PO4, and Me-C(OTBS)=NTBS in refluxing xylenes was optimal, and the methoxycarbonyl group was the most suitable substituent for the nitrogen atom of the carbamimidothioate. Phenyl and alkyl groups can be used as tethers for carbamimidothioates, and alkyl and aryl carbamimidothioates can undergo Pd-catalyzed cycloisomerization in high yields.
MVP-Assisted Temporary Vascular Occlusion during 90Y Radioembolization: A Case Report
Authors: Park John J. , Boas Franz Edward , Pedersoli Federico
Published: January 2024

Yttrium-90 radioembolization is an effective treatment for liver cancers. However, deposition of radioactive microspheres in nondiseased liver can result in parenchymal injury. Segmental and subsegmental radioembolization may reduce off-target liver damage but may not always be possible due to anatomy. In this case report, we highlight the use of a microvascular plug (MVP) to protect distal nondiseased liver and redirect flow into the proximal tumor-containing liver volume during radioembolization of a gallbladder cancer recurrence. Throughout the report, we describe the technique, advantages, and limitations of using MVP-assisted temporary vascular occlusion during organ protection.
On the absence of shock waves and vacuum birefringence in Born–Infeld electrodynamics
Authors: Kadlecová Hedvika
Published: January 2024

We study the interaction of two counter–propagating electromagnetic waves in vacuum in the Born–Infeld electrodynamics. First we investigate the Born case for linearly polarized beams, E · B = 0, i.e., G2=0 (crossed field configuration), which is identical for Born–Infeld and Born electrodynamics; subsequently we study the general Born–Infeld case for beams which are nonlinearly polarized, G2≠0. In both cases, we show that the nonlinear field equations decouple using self-similar solutions and investigate the shock wave formation. We show that the only nonlinear solutions are exceptional traveling wave solutions which propagate with constant speed and which do not turn into shocks for our approximation. We obtain two types of exceptional wave solutions, then we numerically analyze which phase velocities correspond to the counter- or co-propagating beams and subsequently we determine the direction of propagation of the exceptional waves.
Simple modules over the Takiff Lie algebra for sl2
Authors: Zhu Xiaoyu
Published: January 2024

In this paper, we construct, investigate and, in some cases, classify several new classes of (simple) modules over the Takiff sl2. More precisely, we first explicitly construct and classify, up to isomorphism, all modules over the Takiff sl2 that are Uh̄-free of rank one, where h̄ is a natural Cartan subalgebra of the Takiff sl2. These split into three general families of modules. The sufficient and necessary conditions for simplicity of these modules are presented, and their isomorphism classes are determined. Using the vector space duality and Mathieu’s twisting functors, these three classes of modules are used to construct new families of weight modules over the Takiff sl2. We give necessary and sufficient conditions for these weight modules to be simple and, in some cases, completely determine their submodule structure.
Compositional quantum field theory: An axiomatic presentation
Authors: Oeckl Robert , Orendain Almada Juan
Published: January 2024

We introduce Compositional Quantum Field Theory (CQFT) as an axiomatic model of quantum field theory, based on the principles of locality and compositionality. Our model is a refinement of the axioms of general boundary quantum field theory, and is phrased in terms of correspondences between certain commuting diagrams of gluing identifications between manifolds and corresponding commuting diagrams of state-spaces and linear maps, thus making it amenable to formalization in terms of involutive symmetric monoidal functors and operad algebras. The underlying novel framework for gluing leads to equivariance of CQFT. We study CQFTs in dimension 2 and the algebraic structure they define on open and closed strings. We also consider, as a particular case, the compositional structure of 2-dimensional pure quantum Yang–Mills theory.
Chern–Simons field theory on the general affine group, 3d-gravity and the extension of Cartan connections
Authors: Capriotti S.
Published: January 2024

The purpose of this article is to study the correspondence between 3d-gravity and the Chern–Simons field theory from the perspective of geometric mechanics, specifically in the case where the structure group is the general affine group. To accomplish this, the paper discusses a variational problem of the Chern–Simons type on a principal fiber bundle with this group as its structure group. The connection to the usual Chern–Simons theory is established by utilizing a generalization, in the context of Cartan connections, of the notion of extension and reduction of connections.
Fiber reorientation due to obstacles in open channel flow
Authors: Simacek Pavel , Niknafs Kermani Navid , Advani Suresh G.
Published: January 2024

A model along with experimental validation is presented for fiber re-orientation within the flow of a thin fluid layer down an inclined plane. Unlike the usual approach (Jeffery), the model accommodates the fast-changing velocity gradient defying linearization and the flow constraints due to the thin thickness of the fluid film. Model equations are formulated, and the algorithm for the fiber rotation is developed. The velocity field within the channel is obtained, using COMSOLTM multiphase simulation. The formulated model equations are used to track the orientation of a single fiber. The spatial fiber orientation state is described in terms of the second order tensor by tracking multiple individual fibers with different initial orientations. To validate the model's predictions, an experimental setup was fabricated to record individual fiber kinematics during the flow and to describe the orientation of fibers in the open channel. A novel benchmark for assessing fiber re-orientation models is presented, wherein the dynamics of fiber orientation is observed in response to a semicircular obstacle within the fluid flow. The experimental results are compared to model predictions and are in reasonable agreement. Despite the simplified approach, both the dynamic of single fiber and the development of fiber orientation distribution due to the obstacle can be reasonably predicted.
Research on the influence of spanwise cross-flow on the boundary layer transition of compressor cascade
Authors: Li Xiang , Zheng Qun , Chi Zhidong , Wang Shimin , Zhou Zhengtian , Jiang Bin
Published: January 2024

The cross-flow perpendicular to the inviscid main flow in the boundary layer has potential instability, causing the transition from laminar flow to turbulent flow. In order to explore the mechanism of cross-flow in the blade boundary layer on transition, this paper studies the rectangular cascade of a certain compressor stator blade. Large eddy simulation calculations and flow display experiments for six attack angles with end wall cascades were carried out. It is found that the disturbance is dominated by the two-dimensional Kelvin–Helmholtz (K–H) instability. The transition begins at the position where the separation bubble begins to fall off into a two-dimensional K–H vortex and is completed where the K–H vortex breaks. The closer to the blade root, the later the transition occurs and the smaller the total pressure loss. The cross-flow velocity develops alternately between positive and negative, showing severe instability with more than 4 inflection points. The study on variable angles of attack shows that there is a superposition of two mechanisms, namely, separation bubble transition and cross-flow transition, at an angle of attack from −4° to 10°. In summary, although the separation bubble transition is dominated by K–H vortices, the occurrence of cross-flow instability is closely related to the transition position.
An augmented physics informed neural network approach for blunt-body dynamics
Authors: Romeo Shafi Al Salman , Oz Furkan , Kassem Ashraf , Kara Kursat , San Omer
Published: January 2024

This paper presents an ansatz-informed approach to modeling the dynamics of blunt-body entry vehicles by combining physics-based modeling with machine-learning techniques. The main focus is developing an augmented physics-informed neural network (PINN) to simulate the vehicle's behavior during atmospheric entry. The proposed PINN architecture is carefully crafted to incorporate existing knowledge about the fundamental physical principles governing the system. This integration enhances the accuracy and applicability of the model compared to conventional data-driven approaches. The proposed methodology is evaluated across various scenarios and demonstrates precise predictions of the vehicle's trajectory and essential parameters.
Short-term multi-step forecasting of rooftop solar power generation using a combined data decomposition and deep learning model of EEMD-GRU
Authors: Nhat Nam Nguyen Vu , Huu Duc Nguyen , Nguyen Thu Thi Hoai
Published: January 2024

In this study, an integrated forecasting model was developed by combining the ensemble empirical mode decomposition (EEMD) model and gated recurrent unit (GRU) neural network to accurately predict the rooftop solar power output at a specific power unit located in Tay Ninh province, Vietnam. The EEMD method was employed to decompose the solar power signals into multiple frequencies, allowing for a more comprehensive analysis. Subsequently, the GRU network, known for its ability to capture long-term dependencies, was utilized to forecast future values for each decomposition series. By merging the forecasted values obtained from the decomposition series, the final prediction for the solar power output was generated. To evaluate the efficacy of our proposed approach, a comparative analysis was undertaken against other forecasting models, including a single artificial neural network, long short-term memory network, and GRU, all of which solely considered the solar power series as input features. The experimental results provided compelling evidence of the superior performance of the EEMD-GRU model, especially when incorporating weather variables into the forecasting process, achieving the best results in all three forecasting scenarios (1-step, 2-step, and 3-step). For both forecasting targets, Inverter 155 and 156, the n-RMSE indices were 1.35%, 3.5%, and 4.8%, respectively, significantly lower than the compared single models. This integration of weather variables enhances the model's accuracy and reliability in predicting rooftop solar power output, establishing it as a valuable tool for efficient energy management in the region.
Bias-independent subthreshold swing in ballistic cold-source field-effect transistors by drain density-of-states engineering
Authors: Liu Kunyi , Lu Fei , Li Yuan
Published: January 2024

Low power consumption and stable performance insensitive to power supply are highly required for field-effect transistors integrated in portable technologies. Here, we report a mechanism of bias-independent sub-60 mV/dec subthreshold swing (SS) in ballistic cold-source field-effect transistors (CS-FETs) for portable electronics. Our first-principles and quantum-transport simulations demonstrate that, in the ballistic-transport regime, the energy alignment of the number of conduction modes (NOCM) between the drain and source electrodes is critical to achieving bias-independent SS of C31/MoS2-based CS-FETs. By revealing the connection between NOCM and density of states (DOS), we propose a device model to demonstrate how similar slopes of the NOCM and DOS in the drain falling into the gate window can stabilize the SS of the devices under different bias. This study underscores the significance of drain DOS engineering in the design of bias-insensitive CS-FETs for portable electronic applications.
Self-rectifying resistive switching in MAPbI3-based memristor device
Authors: Pham Phu-Quan , Vo Truc-Quyen Thi , Le Duy Khanh , Huynh Chuong Thanh , Ngo Tung Thanh , Nguyen Phuong Tuyet , Pham Anh Tuan Thanh , Vu Nam Hoang , Phan Thang Bach , Kawazoe Yoshiyuki , Pham Ngoc Kim
Published: January 2024

A critical stage in developing high-density memristors is addressing the sneak current within the crossbar architecture. One of the effective strategies to endow the memristive cell with the ability to prevent sneak currents when it is in a low resistance state is to give it an inherent diode, known as a self-rectifying memristive cell. This study demonstrates the Schottky diode inside the MAPbI3-based memristive cell, a consequence of its interaction with the tungsten (W) electrode. The performance of memory devices is reliable with low-voltage operation, a resistance window having over ten of magnitude, and the retention time remains over 104 s. Prominently, the self-rectifying behavior is sustainable over 150 cycles and exhibits a rectification ratio of approximately 102 times. Density functional theory calculation reveals the presence of unoccupied gap states on an interfaced MAPbI3 surface, serving as electron trapping states during the charge transport across the W/MAPbI3 Schottky interface. Consequently, the conduction mechanism is primarily governed by an interfacial-controlled model, notably Schottky emission. This improvement promises to eliminate sneak currents in future crossbar array fabrication.
Building transport models from baroclinic wave experimental data
Authors: Agaoglou M. , García-Garrido V. J. , Harlander U. , Mancho A. M.
Published: January 2024

In this paper, we study baroclinic waves from both the experimental and the theoretical perspective. We obtain data from a rotating annulus experiment capable of producing a series of baroclinic eddies similar to those found in the mid-latitude atmosphere. We analyze the experimental outputs using two methods. First, we apply a technique that involves filtering data using the empirical orthogonal function (EOF) analysis, which is applied to both velocity and surface temperature fields. The second method relies on the construction of a simple kinematic model based on key parameters derived from the experimental data. To analyze eddy-driven fluid transport, we apply the method of Lagrangian descriptors to the underlying velocity field, revealing the attracting material curves that act as transport barriers in the system. These structures effectively capture the essential characteristics of the baroclinic flow and the associated transport phenomena. Our results show that these barriers are in good agreement with the transport patterns observed in the rotating annulus experiment. In particular, we observe that the structures obtained from the kinematic model, or the one derived in terms of filtered velocities, perform well in this regard.
Observation of enhanced WSe2 exciton–exciton annihilation in WSe2/Gr/hBN heterostructure
Authors: Wang Chen , Chen Yu , Sun Kaiwen , Wang Wei , Pu Ruihua , Lin Xian , Liu Weimin , Ma Guohong
Published: January 2024

Due to strong quantum confinement effects and novel physical properties, two-dimensional transition metal dichalcogenides (TMDCs) as well as their heterostructures provide an attractive platform for studying excitonic effects and many-body interactions. However, manipulation on the excitonic effect in TMDCs remains challenge owing to the complex interplay of various factors. In this Letter, we report large exciton peak redshift and enhanced exciton–exciton annihilation in WSe2/Gr/hBN heterostructures investigated with static and transient optical spectroscopy. The pronounced redshift of exciton energy in the triple layer heterostructure arises from the charge transfer effect between graphene and WSe2, which leads to the reduction of the WSe2 exciton binding energy significantly due to the Coulomb screening effect. As a result, the reduced exciton binding energy increases the exciton delocalization in the WSe2 layer, leading to an increased probability of exciton–exciton collisions, which results in fast exciton annihilation rate. This study demonstrates the impact of graphene layer on exciton energy as well as the relaxation dynamics in WSe2/Gr/hBN heterostructures, which provides insights into the understanding of quasiparticle physics and many-body interactions in 2D materials.
Piezoelectric energy harvester with outstanding output performance at low frequency vibration based on concentrating force on the piezoelectric element by parallel springs
Authors: Hao Yifan , Luo Hongzhi , Lu Xinyue , Huang Jiawei , Chen Hang , Yang Tongqing
Published: January 2024

This paper proposes a piezoelectric energy harvester that concentrates force on the piezoelectric element by parallel springs. When vibrating, the force exerted by the mass is released at three equal points on the surface of the brass substrate through three parallel springs. This concentrated release of energy through the spring amplification effect facilitates large deformation of the piezoelectric ceramic sheet, resulting in a higher charge output. The results show that under the combined action of a 14 g annular hollow mass and a 0.3 mm wire diameter stainless steel spring, the energy harvester based on the lead zirconate titanate ceramic exhibited an outstanding output power of 1.0–32.1 mW at a low resonance frequency with acceleration amplitudes of 0.5–3 g (1 g = 9.8 m/s2). More importantly, to match the vibration frequency of the actual environment, this paper optimized the structure of the harvester and proposed that the harvester can be designed by selecting the weight of the mass block, the parameters and number of springs, and the shape of the brass substrate. The energy harvester designed in this study is expected to capture energy from low-frequency natural environments and exhibit outstanding output performance, which can provide guidelines for future efforts in this direction.
Comparing the impact of different adsorbed layers on the local glass transition of polymer matrices
Authors: Thees Michael F. , Merrill James H. , Huang Xinru , Roth Connie B.
Published: January 2024

Chain adsorption to nanofiller interfaces creating bound layers has become central to understanding property changes in polymer nanocomposites. We determine the impact different kinds of adsorbed layers can have on the local glass transition temperature Tg of polymer matrices in a model film system using a localized fluorescence method. This work compares the adsorption and desorption of adsorbed layers grown in solution with the solution washing characteristics of adsorbed layers formed in the melt, leveraging knowledge about polymer adsorption in solution to infer the structure of adsorbed layers formed in the melt. In the limit of zero concentration after a long time in solution, we find that both kinds of adsorbed layers reach the same limiting adsorbed amount h∞(c → 0) ≈ 1 nm, appearing to evolve to the same thermodynamic equilibrium state of a near monolayer of surface coverage. We propose that melt annealing leads to a coarsening of polymer segment–surface contacts, increasing the length of trains and shrinking loops and tails, slowing the subsequent kinetics of these adsorbed chains in solution. Considering how the pyrene-labeled chains intermix with the adsorbed layer enables us to discriminate between the impact of tails, loops, and trains as threading of loops takes longer. We find that large fluffy loops, tails, and trains have little to no impact on the local Tg. A large 30 K increase in local Tg is observed for 30-min solvent washed well-annealed films at long intermixing times that we attribute to the threading of small tight loops.
Strong enhancement of graphene plasmonic emission by quantum Čerenkov effect in confined structures
Authors: Zampa Gian Marco , Mencarelli Davide , Mohebbi Elaheh , Pavoni Eleonora , Pierantoni Luca , Laudadio Emiliano
Published: January 2024

One notable issue in low terahertz (THz) applications is to achieve sources with higher output power than the state of the art. One possible solution to the foregoing problem is to amplify the electromagnetic field emitted by already accessible THz generators. Here, we study the quantum Čerenkov effect as a possible explanation for low-THz amplification, which has been found experimentally elsewhere. Specifically, the emission of surface plasmons from traveling electrons in mono-dimensional graphene, mediated by charge–field interaction, is shown to provide in-plane electromagnetic radiation down to THz and mm-wave frequencies. We focus on a structure consisting of a graphene layer between metal electrodes, which enhance the field confinement and lead to a linearization of the plasmon dispersion in the frequency domain. When compared to a non-confined plasmonic radiation, the above-mentioned configuration shows emission rates ten times larger, which make it promising for THz amplification.
High-efficient spin orbit torque generated by topological semimetal YPtBi deposited on oxidized Si substrates
Authors: Shirokura Takanori , Khang Nguyen Huynh Duy , Hai Pham Nam
Published: January 2024

Half-Heusler alloy topological semimetal YPtBi is a promising candidate for an efficient spin current source in spin–orbit torque (SOT) devices thanks to its large spin Hall angle θSH (>1) and high thermal stability (600 °C). However, the spin Hall effect has been studied so far in high quality YPtBi(111) thin films deposited on c-Sapphire substrates. In this work, we study the SOT performance of sputtered YPtBi films deposited on SiO2/Si substrates. We realized YPtBi(110) thin films with large θSH of 1.3 at a relatively high conductivity of 1.4 × 105 Ω−1 m−1. The spin Hall conductivity of YPtBi(110) is even better than those of YPtBi(111) thin films deposited on c-Sapphire substrates, despite the lower crystal quality. Our results pave the way for using YPtBi in integrated SOT devices on Si substrates.
Dissipation induced instability in porous medium using Brinkman model: Thermal non-equilibrium effect
Authors: Roy Kamalika
Published: January 2024

The convective instability that arises in a porous layer solely because of dissipative energy in the medium is studied. The thermal non-equilibrium model is considered for energy equation. The boundary at top is kept at constant temperature, and an adiabatic lower boundary is considered. The momentum equation is written according to the Brinkman model. A basic flow in the horizontal plane is considered, and the basic velocity and temperature profile have been derived. A comparison between the basic temperature profiles for solid and fluid of the porous medium is presented for Darcy and Brinkman models. Infinitesimal disturbance is introduced to the basic flow. A linear stability analysis has been carried out to study the stability of the basic flow. The parameters influencing the stability of the system are critical Rayleigh number (RaC), Gebhart number (Ge), ξ associated with the Darcy number (Da), and interphase heat transfer coefficient (H). The values of the critical Rayleigh number and wavenumber are compared by varying other variables. The flow is more stable when the Brinkman medium is considered. With the increase in interphase heat transfer coefficient, the critical Rayleigh number increases in both Darcy and Brinkman media. The longitudinal rolls appear as the most unstable rolls for all cases. The variation of convective rolls with respect to ξ and heat transfer coefficient is presented.
On the arbitrary amplitude ion-acoustic structures in an anisotropic non-Maxwellian electron–positron–ion magnetoplasma
Authors: Almas  , Almuqrin Aljawhara H. , Rahman Ata-ur- , Naeem S. Neelam , Matoog R. T. , Ismaeel Sherif M. E. , El-Tantawy S. A.
Published: January 2024

This paper comprehensively investigates the oblique propagation of ion-acoustic solitary waves (IASWs) with arbitrary amplitude in a magnetoplasma consisting of inertialess non-Maxwellian (nonthermal) electrons, inertialess Maxwellian positrons, and inertial adiabatically heated ions. It is postulated that the positive ions demonstrate adiabatic behavior that is distinguished by anisotropic thermal pressure. The study utilizes Sagdeev's pseudopotential theory to analyze the fluid equations of the plasma model and reduce them to the energy equation. Different plasma configuration factors, such as nonthermal parameters, positron concentration, and parallel and perpendicular ion pressure, are being studied to see how they affect the properties of solitary waves with large amplitudes. The findings demonstrate the simultaneous coexistence of compressive and rarefactive IASWs, significantly influenced by positrons and nonthermal electron parameters. The study provides valuable insights into wave phenomena in magnetized plasmas and presents possible applications in both Space and laboratory plasma environments.
Graphene/GaN ultraviolet photodetector performance regulated by a HfO2 insulating layer
Authors: Chen Kun , Li Zexi , Liu Qing , Xu Mingjun , Jiang Qinglong , Dong Zexin , Wang Xingfu , Chen Xinman , Li Shuti , Gao Fangliang
Published: January 2024

The ultraviolet (UV) photodetector is a device that converts optical signals into electrical signals and is the core component of all UV detection systems. A UV photodetector based on a combination of Graphene (Gr, 2D) and GaN (3D) has been reported in this work. High-performance ultra-shallow van der Waals heterojunction ultraviolet photodetectors were realized in this work, and the effects of an interfacial HfO2 tunneling layer on their photoelectric characteristics were investigated in detail. The findings of the study indicated that interfacial defects were effectively repaired by depositing a thin insulating tunneling layer of HfO2 between GaN and Gr using the ALD method with a 3 nm thick layer of HfO2 providing the best results. It was also found that the high-speed carriers underwent ion collision during the tunneling process, resulting in multiplication of the photocurrent. Consequently, the device exhibited a high R value of 318.6 A/W and a large D* value of 1.046 × 1015 Jones under an illuminated power density of 5 μW/cm2 with an external bias voltage of −2 V. The results of this study further validated the application of interfacial engineering technology, while providing insights into the carrier transport mechanism between 2D and 3D materials for the fabrication of high-performance optoelectronic devices.
Vortex dynamics characteristics in the tip region based on Wray–Agarwal model
Authors: Li Wei , Pu Wei , Ji Leilei , Liu Mingjiang , Yang Qiaoyue , He Xinrui , Agarwal Ramesh
Published: January 2024

In order to solve the blockage effect and energy dissipation phenomenon caused by cavitation in the low-pressure vortex core region, this paper analyzes the spatial evolution of vorticity intensity and turbulent kinetic energy intensity under different cavitation conditions based on the Wray–Agarwal (WA) model. First, the tip leakage flow characteristics are studied, the evolution of vorticity and vorticity intensity is analyzed, then the distribution of turbulent kinetic energy distribution in the blade tip region is studied, and finally, the vorticity transport characteristics of the tip region are analyzed. It is found that the tip leakage rate is less affected by the vortex cavitation of the tip leakage, and there is a strong interaction between the leakage flow at the tip leading edge and the trailing edge, and the separation vortices and low-speed regions formed in the end-wall region cause blockage of the flow passage. Low pressure causes cavitation to cover most regions of the suction surface, inhibiting the formation and development of the tip leakage vortices. The distribution range of high turbulent kinetic energy region is almost the same as that of high-vorticity region, and there is a positive correlation between the two intensities. Severe cavitation causes the high turbulent kinetic energy region at the outlet of the flow passage to develop in the radial and axial directions of the impeller, which increases the turbulent dissipation and energy loss. The change of vorticity transport intensity caused by cavitation is mainly reflected in the expansion contraction term, and the Coriolis force term plays a dominant role in the vorticity transport process. This paper provides a reference for further improving the performance of mixed-flow pumps.
Writing and deleting skyrmions by electron beam in van der Waals ferromagnet Fe3GeTe2
Authors: Liu Huibo , Zhang Chenhui , Liu Chen , Chen Aitian , Zheng Dongxing , Peng Yong , Wei Jinwu , Liu Qingfang , Wang Jianbo , Zhang Senfu , Zhang Xixiang
Published: January 2024

Magnetic skyrmions are potential candidates for low-power spintronic devices. Recently, skyrmions have been observed in two-dimensional van der Waals ferromagnets, which extends the range of skyrmion hosting materials to atomically thin limit. However, creating and deleting skyrmions at precise locations is still a challenge for practical applications. In this study, we proposed a solution to this problem. Using in situ Lorentz transmission electron microscopy, we investigated magnetic domain structures in Fe3GeTe2 exfoliated single crystal flakes and found that the skyrmions in this sample are of the Néel type. Interestingly, we found that the skyrmions could be created and deleted at specific locations using a focused electron beam. Micromagnetic simulations results agree well with the experimental results, providing insights into the underlying mechanisms. The methods presented in this work can be extended to other skyrmion material systems, thereby advancing the field of skyrmion-based technologies.
Self-absorption and investigation of excited carrier dynamics in two-dimensional perovskite scintillator
Authors: Yan Weipeng , Duan Baojun , Song Yan , Song Guzhou , Ma Jiming , Li Yang , Li Binkang , Liu Yucheng
Published: January 2024

The PEA2PbBr4 scintillator exhibits varied performance in photoluminescence (PL) and radioluminescence (RL) profiles. PL in the reflectivity mode shows emission peaks at 414 and 434 nm, whereas PL and RL in the transmission mode exhibit only one peak at 434 nm. Temperature-dependent PL spectra measurements confirm that self-absorption contributes to this difference. PEA2PbBr4 displays decay times of 1.3 ns (90%) and 4.4 ns (10%) for PL and 11.5 ns (89%) and 47 ns (11%) for RL. To explain the distinct decay times, we construct two models for simulating laser and radiation excitation and investigate carrier dynamics using non-adiabatic molecular dynamics. Our findings suggest that the relatively long radiative recombination process of carriers contributes to the slow RL decay time.
Synthesis of FCC structure Fe10Co25Ni34Cu23Al8 high-entropy-alloy nanoparticles by electrical wire explosion: For electromagnetic wave absorption
Authors: Liang Liwen , Wu Jian , Yin Zekun , Kong Chuncai , Pervikov A. , Shi Huantong , Li Xingwen , Qiu Aici
Published: January 2024

In this paper, Fe10Co25Ni34Cu23Al8 high-entropy-alloy nanoparticles have been synthesized by the in situ instantaneous electrical wire explosion method. Based on the thermodynamic parameters of the face-centered cubic phase of high-entropy-alloy, the parameters of the five kinds of wires were calculated and controlled, and the stable face-centered cubic structure with good crystallinity was synthesized in one step. The influence of the energy deposition during the electrical explosion on the nanoparticles and their electromagnetic absorption performance was explored. The results show that the face-centered cubic structure high-entropy-alloy with high crystallinity has better electromagnetic wave absorption performance when the energy deposition of the wires is increased. The minimum reflection loss can reach −39.37 dB at 15.34 GHz when the thickness is 1.9 mm and the effective absorption bandwidth is 6.63 GHz. It can provide a strategy for the microstructure and morphology design of high-entropy-alloy nanoparticles in electromagnetic wave absorption and magnetism in the electronics industry.
Highlighting the interdependence between volumetric contribution of fragility and cooperativity for polymeric segmental relaxation
Authors: Trubert Jules , Matkovska Liubov , Saiter-Fourcin Allisson , Delbreilh Laurent
Published: January 2024

The blurring around the link between the isobaric fragility and the characteristic size of cooperative rearranging region for glass-forming liquids has been cleared up by considering volumetric and thermal contributions of the structural relaxation. The measurement of these contributions is carried out for three amorphous thermoplastic polymers using broadband dielectric spectroscopy under pressure, providing an understanding of the link between isobaric fragilities, glass transition temperatures, and microstructures. The cooperative rearranging region (CRR) volume is calculated as a function of pressure using the extended Donth’s approach, and the values are compared with the activation volume at the glass transition under different isobaric conditions. By combining these different results, a link between the chemical structure and the influence of pressure/temperature on the molecular mobility can be established. Furthermore, this study shows also a strong correlation between the activation volume, leading to the volumetric contribution of the isobaric fragility, and the CRR volume. Finally, this work highlights the influence of inter- and intra-molecular interactions on thermal and volumetric contributions of the isobaric fragility as a function of pressure.
Anisotropic frictional model for an object sliding in a granular media
Authors: Zuñiga René , Vasconcellos Carlos , Darbois Texier Baptiste , Melo Francisco
Published: January 2024

Several locomotion strategies are based on the anisotropic nature of the forces experienced by the moving body with its environment. We report experiments on the anisotropy of the frictional force experienced by a cylinder moving in a granular medium as a function of the orientation α between the cylinder and its velocity. The component of the force in the direction parallel to the velocity of the cylinder is always higher than the perpendicular component; therefore, the force is anisotropic. While the parallel component increases continuously with the cylinder angle α, we observe that the perpendicular component reaches a maximum value for an orientation of αc≃35°. To rationalize these observations, we have developed a theoretical model, which assumes that the mechanical energy required to move the cylinder is dissipated by friction and establishes a relationship between the parallel and perpendicular force components that is consistent with experiments.
Strong coupling between excitons and quasi-bound states in the continuum mode with stable resonance wavelength in the near-infrared region
Authors: Gao Chenggui , You Shaojun , Zhang Ying , Wang Lulu , Duan Hong , He Haoxuan , Xie Quan , Zhou Chaobiao
Published: January 2024

Strong coupling between photons and excitons gives rise to Rabi splitting and hybridized states. These exhibit spectral anticrossing behavior and ultrafast energy exchange, demonstrating remarkable nanophotonic properties and offering exciting application possibilities. Herein, we propose a metasurface based on dimeric MoTe2 nanodisks for flexible control of the strong coupling between quasi-bound states in the continuum (QBIC) and excitons in the near-infrared region. It was found that introducing a gap perturbation transforms the BIC into a QBIC with a stable resonance wavelength, and the gap width can be used to customize its Q-factor. We confirmed that the upper limit of the Q-factor for achieving strong coupling is 500 in this QBIC metasurface system. It is noted that the wavelength of the QBIC mode and exciton peak are stable, so the coupling strength can be easily adjusted using the disturbance parameters. Moreover, significant Rabi splitting and typical anticrossing behavior were observed when the thickness and radius of the dimeric MoTe2 nanodisks were varied. The Rabi splitting value was 170 meV for f0=1.0. This work provides a useful solution for strong coupling in the near-infrared region, which may pave the way toward tunable near-infrared exciton polariton devices with high compatibility.
Solute interaction-driven and solvent interaction-driven liquid–liquid phase separation induced by molecular size difference
Authors: Iida Yuya , Hiraide Shotaro , Miyahara Minoru T. , Watanabe Satoshi
Published: January 2024

We conducted molecular dynamics (MD) simulations in a binary Lennard-Jones system as a model system for molecular solutions and investigated the mechanism of liquid–liquid phase separation (LLPS), which has recently been recognized as a fundamental step in crystallization and organelle formation. Our simulation results showed that LLPS behavior varied drastically with the size ratio of solute to solvent molecules. Interestingly, increasing the size ratio can either facilitate or inhibit LLPS, depending on the combination of interaction strengths. We demonstrated that the unique behavior observed in MD simulation could be reasonably explained by the free energy barrier height calculated using our thermodynamic model based on the classical nucleation theory. Our model proved that the molecular size determines the change in number of interaction pairs through LLPS. Varying the size ratio changes the net number of solute–solvent and solvent–solvent interaction pairs that are either broken or newly generated per solute–solute pair generation, thereby inducing a complicated trend in LLPS depending on the interaction parameters. As smaller molecules have more interaction pairs per unit volume, their contribution is more dominant in the promotion of LLPS. Consequently, as the size ratio of the solute to the solvent increased, the LLPS mode changed from solute-related interaction-driven to solvent-related interaction-driven.
Effects of various geometric parameters on the computed swirl numbers and flow topology in a bidirectional vortex chamber
Authors: Sharma Gaurav , Majdalani Joseph
Published: January 2024

A finite-volume solver is used to compute the cyclonic motion in a vortex chamber assuming steady, incompressible, and inviscid flow conditions. A parametric campaign enables us to characterize the computed swirl number over a wide range of properties. These include the tangential injection speed, number of injectors, injector port diameter, axial injection plane, and outlet fraction. In addition to the traditional swirl number, both geometric and modified swirl numbers are evaluated. In this process, the characteristic values of all three swirl numbers are determined over a wide range of design and inflow parameters. Overall, the geometric and modified swirl numbers are seen to follow similar trends, being different by a constant multiplier, with the former ranging between 0.9 and 410. We also find that increasing the injection speed has no bearing on the swirl numbers. In contrast, adding more injectors leads to a linear decrease in the swirl number, except for the case of a single injector. Although expanding the injector diameter initially results in larger swirl numbers, these begin to diminish after reaching an optimal diameter. Moreover, as the injection plane is displaced toward the headwall, the swirl number is reduced while remaining positive as long as a coherent cyclonic motion is present. As the injection plane is raised above the chamber midsection plane, the traditional swirl number turns negative. Varying the normalized outlet radius β is also found to affect the pressure and velocity distributions, with a central recirculation zone emerging beyond β = 0.707 and leading to vortex breakdown past β = 0.866.
Impurity reduction in lightly doped n-type gallium nitride layer grown via halogen-free vapor-phase epitaxy
Authors: Kimura T. , Shimazu H. , Kataoka K. , Itoh K. , Narita T. , Uedono A. , Tokuda Y. , Tanaka D. , Nitta S. , Amano H. , Nakamura D.
Published: January 2024

The development of gallium nitride (GaN) vertical-type metal-oxide-semiconductor field-effect transistors and p–i–n diode devices has gathered increasing attention. These devices require an n-type drift layer with a low doping level of 1016 cm−3 or less, minimized point defects inhibiting electron conduction, and a layer approximately 10 μm thick. Therefore, a practical method with a growth rate of at least several tens of μm/h and impurity concentrations of less than 1015 cm−3, except for that of dopants, is necessary. Halogen-free vapor-phase epitaxy (HF-VPE) has a high growth rate suitable for fabricating thick drift layers and utilizes a simple reaction between Ga vapor and ammonia gas (without a corrosive halogen gas), resulting in lower impurity levels. Herein, we eliminated the quartz content from the high-temperature zone to reduce the excess unintentional Si doping and identified that the nitrile gloves used for the growth preparation are other impurity contamination sources. We obtained a lightly n-type ([Si]=∼1016 cm−3) GaN layer, in which C, O, B, Fe, Mg, Al, Ca, Cr, Zn, Ni, Mn, and Ti impurity contents were below the detection limits of secondary ion mass spectrometry. Deep-level transient spectroscopy revealed that electron traps at EC − 0.26 and at EC − 0.59 eV were 2.7 × 1013 and 5.2 × 1014 cm−3, respectively. Moreover, the Hall effect analysis showed the acceptor-type defect-compensating donor content as approximately 2.7 × 1015 cm−3, resulting in a high electron mobility of HF-VPE GaN in the 30–710 K temperature range. Furthermore, we identified the Ca impurity as a deep acceptor, another killer defect leading to mobility collapse.