bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved All Select Relay Selection Protocol with Limited Feedback Information for Decode and Forward Free Space Optical Communication
Authors: Shrivastava Shreesh Kumar
Published: November 2024

In all select relay selection protocol using decode and forward (DF) relaying techniques, the source transmits data to every relay that is currently connected to the network. Only relays that successfully decode the data they receive will forward it to the intended destination after completing the necessary signal processing. As a result, the network no longer incorporates those source to relay links that did not receive the signal correctly. In addition, all the energy that was put into these connection is now wasted. In light of this, in this paper, I propose the concept of limited feedback (from relay to source) to determine the transmitted power of each source to relay (S-R) connection, ensuring that all links continue to function and contribute to data transmission. This brief feedback consists of a few bits that provide the relay identification and the instantaneous power requirement.
Experimental Investigation on E-Waste Concrete Using Mineral Admixtures
Authors: Thulasirajan K. , Sai Keerthi P. , Lokesh D. , Shiva Shankar Naik N. , Sreekanth Y. , Hemanth M.
Published: November 2024

Our reliance on electronics, a cornerstone of modern life, comes at a cost. The relentless pace of technological advancement generates mountains of discarded devices, creating the growing problem of electronic waste. This E-waste, if improperly disposed of, can contaminate landfills and release harmful materials into the environment. This study investigates a potential solution: using a portion of e-waste in place of fine aggregate. To improve overall performance, we also incorporate mineral admixtures. Our research aims to understand how both the amount of e-waste and the specific mineral admixtures used influence the final properties of the concrete. We systematically replaced the fine aggregate with e-waste at varying percentages (0%, 10%, 20%, and 30%) and meticulously analyzed the resulting effects. The study identifies 10% e-waste replacement as the optimal level for achieving desirable properties in M20 grade concrete, a commonly used strength classification. This approach offers a two-fold benefit. It tackles the e- waste crisis by providing a sustainable disposal option, and it potentially reduces the construction industry's reliance on virgin resources like natural sand, contributing to a more sustainable future.
The Effectiveness of the Number Head Together (NHT) Type Cooperative Learning Model to Improve Arabic Language Learning Outcomes for Grade 7 Students of SMP Muhammadiiyah 5 Yogyakarta
Authors: Wat Ana Taqwa , Himawati Zulfa
Published: November 2024

The learning model greatly affects student learning outcomes. Most of the 7th grade students of SMP Muhammadiyah 5 Yogyakarta, think that Arabic lessons are difficult to understand because the learning model used is boring. Therefore, the researcher took the NHT Type cooperative learning model as a solution that suits the situation of students in grade 7 of SMP Muhammadiyah 5 Yogyakarta. This study aims to determine the effectiveness of the NHT-type cooperative learning model in improving the learning outcomes of Arabic subjects. The research method used was quantitative using the True-Experimental pseudo-experimental research method with a Postest only control group design. The researcher will use 4 classes, namely 7B, 7C, 7D and 7E totaling 107 students as the population and 50 samples. This study used two groups, namely the experimental group and the control group by providing treatment and postest to each class. The sampling used by the researcher is Probability sampling, the researcher uses a data collection method The test used is a test of student learning outcomes after using the NHT or posttest type learning model. The results showed that the NHT type cooperative learning model was effective in improving the learning outcomes of Arabic language for grade 7 students of SMP Muhammadiyah 5 Yogyakarta. This is evidenced by the results of the analysis of the independent sample t test, it is known that the value of sig 2 tailed 0.000 is less than 0.05, then Ho is rejected and Ha is accepted or there is a significant difference in the average learning outcomes of students who use the NHT model and learning that does not use the NHT model.
Activities and barriers in online professional development: A systematic literature review
Authors: Iswati Luluk , Hastuti Saptin Dwi Setyo
Published: November 2024

Despite the increased use of technology to facilitate English teachers’ professional development, there is a lack of comprehensive review of the employed activities and barriers. The current study aims to comprehensively look into the landscape of online professional development activities and the encountered barriers. Employing a systematic literature review approach, activity types and barriers of online professional development were identified. Through rigorous methodology, including database searches and inclusion criteria, 18 studies conducted in diverse global contexts were reviewed. The findings reveal four categorized professional development activities: structured learning, mentoring, informal learning, knowledge sharing, and social interaction. Barriers encompass attitudinal, physical, and structural factors such as negative attitudes, internet connectivity issues, and collaboration difficulties. The study concludes that effective communication, tailored solutions, and stakeholder collaboration are essential for overcoming the barriers of online professional development. The findings imply the crucial roles of stakeholders in enhancing online professional development for teachers. Future research should address the interplay of the barriers, their impacts, and innovative strategies.
Translation Techniques of Mechanical Engineering Terms in English for Engineering Book by Mechanical Engineering Students
Authors: Farahsani Yashinta , Ani Puji Setiawati Sri , Handung Jaya Patria
Published: November 2024

Translators often face challenges when dealing with unfamiliar terms, particularly in specialized fields like mechanical engineering. This study investigates the translation techniques employed by students in the Mechanical Engineering Study Program at Universitas Muhammadiyah Yogyakarta, Indonesia, when translating texts from English for Engineering textbook. The research involved six classes, each with 35-40 students, and applied 18 translation techniques based on Molina & Albir’s (2002) theory. The study revealed that literal translation (57.89%) and natural borrowing (29.82%) are the most frequently used techniques, ensuring precision and clarity in technical documentation. However, common translation errors include inconsistent terminology, lack of context, and failure to localize technical terms. The results suggest that students’ translation choices are influenced by their limited English vocabulary and reliance on English reference materials. Recommendations include enhancing students’ vocabulary and translation skills to improve accuracy and consistency in technical translations, thereby supporting better global collaboration in mechanical engineering.
Das therapeutische Potenzial von extrazellulären Vesikeln von
mesenchymalen Stromazellen
Authors: Kutzner Tanja J. , Bauer Fabiola Nardi , Giebel Bernd
Published: November 2024

Kleine (small) extrazelluläre Vesikel (sEVs) sind biologische Nanopartikel
mit Größen von unter 200 nm, die von praktisch allen Zellen freigesetzt und in
allen Körperflüssigkeiten nachgewiesen werden können. Ihre Zusammensetzung ist
zellspezifisch, und ein Teil der sEVs kann komplexe Informationen von der
sendenden zu spezifisch ausgewählten Zielzellen übertragen. Abhängig von ihrem
Ursprung können sEVs physiologische und pathophysiologische Prozesse steuern.
sEVs, die von mesenchymalen Stamm-/Stromazellen (MSCs) freigesetzt werden,
vermitteln beispielsweise therapeutische Aktivitäten bei einer Vielzahl
verschiedener Krankheiten, deren Symptomatik von Entzündungsprozessen geprägt
ist. Obwohl ihre konkreten Wirkmechanismen (mode of action; MoA) sowie
ihre Wirkorte (side of action; SoA) noch nicht ausreichend untersucht
wurden, scheint es, dass MSC-sEVs multimodal wirken. Es gibt Hinweise darauf,
dass MSC-sEV-Präparate als Teil ihrer therapeutischen Aktivitäten
pro-inflammatorische in regulatorische/tolerogene Immunantworten umwandeln,
angiogene und pro-regenerative Prozesse fördern sowie anti-apoptotisch und
energieerhaltend wirken. Hier beschreiben wir die Historie, die zur Entdeckung
der therapeutischen Aktivitäten von MSC-sEVs geführt hat, einige ihrer
therapeutischen Anwendungsfelder und Herausforderungen bei ihrer effektiven
Translation in die Klinik.
Antikörpertestung in der Nierentransplantation
Authors: Dick Andrea , Kugyelka Reka , Humpe Andreas , Kauke Teresa
Published: November 2024

Das HLA-System (HLA: humane Leukozytenantigene) spielt eine wichtige Rolle bei
der Transplantation (Tx) der Niere. Daher ist der Nachweis von HLA-Antikörpern
vor und nach der Tx entscheidend für die Betreuung des Patienten, wobei
verschiedene Verfahren eingesetzt werden. Der Nachweis von donorspezifischen
HLA-Antikörpern (DSA) ist gemäß Banff-Klassifikation [1] ein wichtiges Kriterium
für die Diagnostik der antikörpervermittelten Abstoßung (ABMR:
„antibody-mediated rejection“). Die Untersuchung auf präformierte sowie auf de
novo DSA zu verschiedenen Zeitpunkten nach der Tx kann helfen, das individuelle
Risiko für eine ABMR zu beurteilen.
Controlled molecule injector for cold, dense, and pure molecular beams at the European x-ray free-electron laser
Authors: He Lanhai , Johny Melby , Kierspel Thomas , Długołęcki Karol , Bari Sadia , Boll Rebecca , Bromberger Hubertus , Coreno Marcello , De Fanis Alberto , Di Fraia Michele , Erk Benjamin , Gisselbrecht Mathieu , Grychtol Patrik , Eng-Johnsson Per , Mazza Tommaso , Onvlee Jolijn , Ovcharenko Yevheniy , Petrovic Jovana , Rennhack Nils , Rivas Daniel E. , Rudenko Artem , Rühl Eckart , Schwob Lucas , Simon Marc , Trinter Florian , Usenko Sergey , Wiese Joss , Meyer Michael , Trippel Sebastian , Küpper Jochen
Published: November 2024

A permanently available molecular-beam injection setup for controlled molecules (COMO) was installed and commissioned at the small quantum systems (SQS) instrument at the European x-ray free-electron laser (EuXFEL). A b-type electrostatic deflector allows for pure state-, size-, and isomer-selected samples of polar molecules and clusters. The source provides a rotationally cold (T ≈ 1 K) and dense (ρ ≈ 108 cm−3) molecular beam with pulse durations up to 100 µs generated by a new version of the Even-Lavie valve. Here, a performance overview of the COMO setup is presented along with characterization experiments performed both with an optical laser at the Center for Free-Electron-Laser Science and with x rays at EuXFEL under burst-mode operation. COMO was designed to be attached to different instruments at the EuXFEL, in particular, the SQS and single particles, clusters, and biomolecules (SPB) instruments. This advanced controlled-molecules injection setup enables x-ray free-electron laser studies using highly defined samples with soft and hard x-ray FEL radiation for applications ranging from atomic, molecular, and cluster physics to elementary processes in chemistry and biology.
Thermoelectric properties of Janus BiXI (X = S and Se) monolayers: A first-principles study
Authors: Xiong Guo-huan , Liu Te , Huang Hai-hong , Wang Jian
Published: November 2024

Janus monolayers, a novel class of two-dimensional materials, have attracted significant interest owing to their asymmetric atomic arrangement. In this work, we systematically investigate the thermoelectric properties of Janus BiXI (X = S and Se) monolayers, using first-principles calculations and semiclassical Boltzmann transport theory. These dynamically stable BiSI and BiSeI monolayers exhibit indirect bandgaps of 0.870 and 0.797 eV, respectively, when accounting for the spin–orbit coupling effects. The Janus BiSeI monolayer exhibits a lower lattice thermal conductivity of 0.168 W/mK at 300 K, attributed to the increased phonon-scattering channels and enhanced anharmonicity introduced by the heavier Se atom. Furthermore, the Janus BiSeI monolayer demonstrates a superior Seebeck coefficient and high electrical conductivity, resulting in a significantly enhanced power factor. Consequently, the Janus BiSeI monolayer exhibits a higher figure of merit (ZT) value, with 0.895 at 300 K and 2.466 at 700 K, compared to the Janus BiSI monolayer, which has ZT values of 0.158 at 300 K and 0.591 at 700 K. These findings establish the Janus BiSeI monolayer as an excellent candidate for thermoelectric conversion applications. The understanding may have broader implications for the exploration of 2D thermoelectric materials.
Applications of microfluidics in mRNA vaccine development: A review
Authors: Fardoost Ali , Karimi Koosha , Govindaraju Harshitha , Jamali Pegah , Javanmard Mehdi
Published: November 2024

The transformative potential of microfluidics in the development of mRNA vaccines is explored in this review, highlighting its pivotal role in enhancing easy-to-use functionality, efficacy, and production efficiency. Moreover, we examine the innovative applications of microfluidics in biomedical research, including its contribution to the rapid and cost-effective synthesis of lipid nanoparticles for mRNA delivery and delve into the advantages of mRNA vaccines, such as targeted delivery and controlled expression. Furthermore, it outlines the future prospects of microfluidic devices, their cutting-edge examples in both research and industry, and the potential to revolutionize vaccine formulation and production. The integration of microfluidics with mRNA vaccine development represents a significant advancement in public health and disease prevention strategies.
Hidden multi-scroll and coexisting self-excited attractors in optical injection semiconductor laser system: Its electronic control
Authors: Mengue A. D. , Essimbi B. Z.
Published: November 2024

In this paper, we investigate hidden and coexisting self-excited multi-scroll attractors by using a modified rate equations model of semiconductor lasers (REM-SCLs) subjected to optical injection by exploring various quantifying analytical and numerical methods. The multi-leveled dynamics sticks out the existence of several sets of equilibria that asymptotically attract trajectories originating outside of them. Chaos topology based on the impact of equilibria allows the describing of the so-called stable or unstable multi-scroll chaotic attractors. Shaping of the new coexisting self-excited multi-scroll attractor, whose source is from coupling of equilibria, is analyzed, as well as its structural dynamics along with the dynamical emergence of the hidden multi-scroll attractor in the restricted interval, defined by an additional decisive parameter. Additionally, specific 3D plots with embedded contour plots obtained by harnessing two-parameter bifurcation analysis clarify structural dynamics of such a multi-scroll attractor and accurately circumscribe stretching of its fractal-like basin of attraction. Strange metamorphoses undergone by the fractal-like basin of attraction of the studied multi-scroll attractor are stepwisely parsed in the map of two-codimension bifurcation as its scroll number evolves. At last, an electronic circuit of equivalent REM-SCLs is designed and simulated in the PSpice environment alongside a tailored electronic controller. The achieved results align with the ones of numerical analysis; besides, temporal controlling of optical waves pertaining thereto is also fulfilled.
Inorganic thermoelectric semiconductors with room temperature plasticity
Authors: Wang Yuechu , Fu Chenguang , Shi Xun , Chen Lidong , Zhu Tiejun
Published: November 2024

The rapid growth of wearable electronics, health monitoring, and the Internet of Things has created a tremendous demand for flexible semiconductors and gadgets. Thermoelectric (TE) semiconductors that enable direct conversion between heat and electricity have been utilized as power generators, but their intrinsic brittleness inhibits the application for powering flexible/wearable electronics. The plastic inorganic semiconductors discovered in recent years offer a different option for flexible TE technologies when these materials combine good plasticity and high TE performance at room temperature. In this Perspective, we discuss how room-temperature plasticity affects the manufacturing process and real-world uses in flexible electronics, the trade-off between plasticity and thermoelectric performance, and the underlying deformation mechanisms. Further outlook on the discovery of viable plastic inorganic semiconductors is proposed.
Mn3Sn-based noncollinear antiferromagnetic tunnel junctions with bilayer boron nitride tunnel barriers
Authors: Wang Zhanran , Bian Bo , Zhang Lei , Yu Zhizhou
Published: November 2024

Electrical manipulation and detection of antiferromagnetic states have opened a new era in the field of spintronics. Here, we propose a noncollinear antiferromagnetic tunnel junction (AFMTJ) consisting of noncollinear antiferromagnetic Mn3Sn as electrodes and a bilayer boron nitride as the insulating layer. By employing the first-principles method and the nonequilibrium Green's function, we predict that the tunneling magnetoresistance (TMR) of the AFMTJ with AA- and AB-stacked boron nitride can achieve approximately 97% and 49%, respectively. Moreover, different orientations of the Néel vector in the electrodes lead to four distinct tunneling states in the Mn3Sn/bilayer BN/Mn3Sn AFMTJ. The TMR ratio could be notably improved by adjusting the chemical potentials, reaching up to approximately 135% at a chemical potential of 0.1 eV for the AFMTJ with AA-stacked boron nitride. This enhancement can be primarily attributed to the reduction in the transmission of antiparallel configurations around the K and K′ points in the two-dimensional Brillouin zone. Our findings could provide extensive opportunities for all-electrical reading and writing of the Néel vector of noncollinear antiferromagnets, paving the way for the development of antiferromagnetic tunnel junctions with two-dimensional tunnel barriers.
Impact of depth-ratio on shear-layer dynamics and wake interactions around wall-mounted prisms
Authors: Goswami Shubham , Hemmati Arman
Published: November 2024

This numerical investigation explores the flow dynamics around wall-mounted prisms with small aspect-ratio (AR=0.25−1.5) and changing depth-ratio (streamwise length, DR=1−4) at a Reynolds number of Re=1000−2500. This study focuses on understanding the formation and evolution of Kelvin–Helmholtz Instability (KHI) and its interactions with coherent wake structures, e.g., hairpin-like vortices. Additionally, it examines the influence of depth-ratio on prism surface pressure distribution and the origin of pressure fluctuations. The results, driven from the extreme geometrical cases of AR=1, DR=1 and 4 at Re=2500, reveal distinct KHI rollers originating from the leading edge shear layer. These impact prism surface pressure distribution and contribute to downstream wake structures. Interactions between KHI rollers and coherent wake structures are more pronounced for larger depth-ratio prisms, leading to a complex wake system. These interactions are quantified using turbulence–mean-shear interaction and turbulence–turbulence interaction from analyzing the Poisson equation. Cross-spectral density analysis highlights the influence of KHI rollers on coherent structures in the wake. These findings emphasize the significance of depth-ratio in shaping prism flow dynamics.
Computational modeling of boiling droplets of multi-component fuels integrating bubble evolution: A review and enhancement
Authors: Liu Zihe , Jia Ming , Cai Yikang , Zhang Yanzhi , Liu Hong
Published: November 2024

With the utilization of new practical fuels in engines, including mixed fuels, the droplet evaporation model may not adequately describe the phenomenon of the multi-component fuel droplets undergoing boiling at high ambient temperatures due to the large difference in the boiling points between the different components. Therefore, the construction of the droplet boiling model becomes important to broaden the applicability of the droplet vaporization model in engine simulations. In this study, a comprehensive evaluation framework for the boiling droplet model, which integrates bubble evolution, is constructed. The available sub-models of bubble nucleation, growth, and breakup are analyzed and evaluated. Then, the validation and comparison of the droplet vaporization model integrating bubble evolution for multi-component fuels are systematically conducted under wide conditions. The results indicate that the accuracy of the bubble evolution sub-models determines the prediction accuracy of the droplet boiling model. The enhanced bubble sub-models, taking into account the effects of the liquid viscosity, surface tension, and molecular diffusion of the multi-component droplet, show satisfactory performance in predicting the boiling behavior of the multi-component droplets, and reduce the choice of empirical parameters in applications. The updated droplet vaporization model integrating the enhanced bubble sub-models aligns more consistently with the actual physical processes at high-temperature environments, enabling quantitative reproduction of the fluctuation and evolution of the droplet diameter in the boiling stage. Moreover, it is found that the accuracy of the droplet vaporization model is significantly influenced by the prediction of the boiling critical point of the multi-component mixture, and the change of the bubble point of the liquid mixture with the liquid composition and operating conditions should be considered.
Atomic scale observation of threading dislocations in α-Ga2O3
Authors: Mullen Ross , Roberts Joseph W. , Chalker Paul R. , Oliver Rachel A. , Hourahine Ben , Massabuau Fabien C. P.
Published: November 2024

This study presents a statistically significant investigation of threading dislocations in α-Ga2O3 using high-resolution transmission electron microscopy. All the dislocations, observed end on, exhibit a projected Burgers vector be=13⟨11̄00⟩, with data revealing that the dislocations fall into three categories: perfect mixed (b=13⟨11̄01⟩) dislocations and edge (b=⟨11̄00⟩ and b=13⟨112̄0⟩) dislocations, which dissociate into combinations of b=13⟨11̄00⟩ partials. High-resolution analysis of the core region of the dislocations identifies that all the dislocations exhibit a similar 5-atom core, when looking at the cation sites. This is the first investigation of its kind in this material system, which will inform future work to, for example, understand the electronic properties of dislocations in α-Ga2O3 and other epitaxial corundum-structured materials.
Numerical and experimental investigation of rarefied hypersonic flow in a nozzle
Authors: Jin Xuhong , Su Penghui , Chen Zhi , Cheng Xiaoli , Wang Qiang , Wang Bing
Published: November 2024

A combined computational/experimental study is performed to investigate hypersonic low-density internal gas flows in a convergent-divergent nozzle over a wide range of Knudsen numbers. The numerical solutions are obtained using the direct simulation Monte Carlo (DSMC) method and the experimental measurement is conducted in the hypersonic low-density wind tunnel FengDong-19 (FD-19) at China Academy of Aerospace Aerodynamics. Rarefaction effects are found to play an important role in pressure disturbance propagation, flow separation (vortex formation), mass flow rate, velocity slip, and thermally nonequilibrium effect. Pressure disturbance propagates farther upstream with increasing free-stream Knudsen number Kn∞. Although there is no flow separation near the nozzle surface for Kn∞ = 0.1, the slip velocity is such anomalously small that it cannot suppress flow separation, thus, producing one small vortex for Kn∞ = 0.2, 0.5 and 1. Due to the presence of the continuous sheet of two-order Moffatt vortices, the skin friction coefficient does not change sign (positive to negative) in the small separated region. This indicates that the incipient and small separated flows with second-order vortices may not be discerned by examining the sign of the skin friction. As Kn∞ grows to 2, this small vortex disappears. However, with further increase in Kn∞, a large vortex nearly fills the compression section of the nozzle due to the backflow effect. As Kn∞ increases from continuum to free molecular regime, the dimensionless mass flow rate mfr/mfr∞ rises first to its maximum at Kn∞ ∼ 0.2 resulting from the weaker flow blockage effect. After the maximum point, mfr/mfr∞ dwindles first because of the stronger backflow effect and rises again to its free molecular limit, obtaining its minimum (the so-called Knudsen minimum) at Kn∞ ∼ 10. DSMC results and experimental data obtained from FD-19 wind tunnel are in good agreement, achieving a mutual validation between computation and experiment. This indicates that our experiment provides valuable data that can server as “benchmark” case to support computational code evaluation and validation.
Isotropic ↔ anisotropic surface geometry transitions induced by adsorbed surfactants at water/vapor interfaces
Authors: Kumar Nitesh , Bilsky Joshua , Clark Aurora E.
Published: November 2024

Adsorbates at a water/vapor interface change the surface geometry through altered surface tension, yet detailed theoretical studies are relatively sparse, and many applications focus on ensemble average characteristics. Here, we demonstrate that different interpretations of surface geometry emerge when considering the distributions of surface curvature and orientation as a function of adsorbed surfactant concentration and sterics. At low surface densities, the tributyl phosphate (TBP) sorbed water/vapor surface has an increased presence of ridges that are defined by principal curvatures κ1 and κ2 of opposite signs yet close in magnitude. As the TBP surface density increases, the difference in principal curvatures slowly increases. There is a distinct transition of the surface geometry, where the ridge-like features become much more pronounced, having sides whose orientation is normal to a flat interfacial plane. Thus, as the TBP surfactant is added to the surface, the surface curvatures become anisotropic in terms of the difference in magnitude of κ1 and κ2. We label this an isotropic → anisotropic geometric transition. Comparing the surface geometry as a function of the carbon tail length of the alkyl phosphate surfactant reveals that smaller surfactants also anisotropically enhance surface curvatures and that adsorbed alkyl tails to the surface stabilize and increase the symmetry of surface waves along the two principal curvature axes. We label this an anisotropic → isotropic geometric transition. These results reflect the opportunity to incorporate more realistic distributions of surface geometry within the collective understanding of statistical theories of surfaces, including capillary wave theory.
Coaxial and non-coaxial collisions between vortex rings and stationary spheres
Authors: Xu Bowen , New T. H.
Published: November 2024

A large-eddy simulation-based study has been carried out focusing on the coaxial and non-coaxial collisions between a ReΓ0=3000 vortex ring and stationary spheres. The effect of sphere size on vortex dynamics was investigated by varying the sphere-to-vortex ring diameter ratio, D/d, from 1 to 4 (where D and d are the sphere and vortex ring diameters, respectively). Four offset distances ranging from δ/D=1/8 to 1/2 were used for non-coaxial collisions. Coaxial configurations produce vortex ring collision outcomes that are increasingly restricted to the upper part of the sphere as the diameter ratio increases. In contrast, non-coaxial configurations lead to progressively more asymmetric vortex ring collisions that feature nonuniform formations and entrainment of secondary and tertiary vortex rings. This in turn produces circumferential flows from the end closer to the sphere (near-end) to the end further away from the sphere (far-end), where they become stronger as the offset distance increases. As such, near-end primary vortex ring segments experience vortex stretching, while their far-end counterparts undergo compression. Temporal variations in circulation and vortex-stretching levels as the collisions unfold are presented to quantify these flow differences. Additionally, secondary vortex ring behavior underpins the key collision phenomena observed in non-coaxial collisions across the different spheres, reinforcing their important role in the collision mechanism. Finally, present results demonstrate that the relative sphere size matters less beyond a critical diameter ratio, while the offset distance becomes increasingly important in non-coaxial collisions.
Effect of solid particle size on cavitation around hydrofoil
Authors: Lin Zhe , Liu Hang , Zhang Guang , Li Linmin
Published: November 2024

Pumps and turbines are widely used in marine engineering, and hydrofoil cavitation, a fundamental form of pump and turbine cavitation, is often used as a simplified hydraulic model to study cavitation issues. However, oceans and lakes contain many particulate impurities that can exacerbate the instability of the cavitation flow field around hydrofoils. Currently, there are few studies on solid particle-induced cavitation in hydrofoils. To investigate the influence of small particles on blade cavitation, the National Advisory Committee for Aeronautics 0006 hydrofoil was used as a simplified blade model. Using the large eddy simulation-volume of fluid method and the discrete phase model, the three-dimensional cavitation flow field around the hydrofoil was analyzed for nine different particle sizes at a 3% particle concentration and compared to the flow field in clean water. The results show that small particles cannot penetrate the bubble film but move along the surface of the cavity, slightly increasing the vortex and turbulence intensity within the cavitation flow field, thereby promoting cavitation development and reducing the hydrofoil's hydrodynamic performance. As particle size increases, the overall effect of particle number becomes stronger, while the reduction of particle number leads to a reduced impact of small particles on the cavitation flow field.
Extension of the local domain-free discretization method to large eddy simulation of compressible flows
Authors: Zhang Dian , Zhou Chunhua
Published: November 2024

Most of the flow problems encountered in practical engineering are wall-bounded turbulent flows at high Reynolds numbers. Wall-modeled large eddy simulation (WMLES) is one of the most viable approaches for predicting these realistic flows. Immersed boundary (IB) approach is an efficient computational technique to solve flow problems involving complex and/or moving geometries. This work extends a sharp-interface IB method, named the local domain-free discretion (DFD), to WMLES of compressible flows at high Reynolds numbers. An equilibrium wall model based on solving the simplified compressible turbulent boundary layer equations is utilized to alleviate the requirement of high near-wall mesh resolution. In conjunction with the approximate boundary conditions prescribed by the modeled wall shear stress and wall heat flux, the tangential velocity and temperature at an exterior dependent node are evaluated. Then, the closure of the discrete form of governing equations at an interior node in the immediate vicinity of the immersed wall is accomplished. A simple non-equilibrium correction of the wall shear stress provided by the equilibrium wall model is introduced explicitly. The WMLES/DFD method is applied to a supersonic zero-pressure-gradient turbulent boundary layer flow, a shock wave/flat-plate boundary layer interaction, a supersonic compression ramp flow and high-speed turbulent Couette flows with various thermal boundary conditions. The influence of grid resolution is investigated in the simulation of zero-pressure-gradient turbulent boundary layer flow. By comparing the computed results with the referenced experimental data and/or numerical results, the accuracy and ability of the WMLES/DFD method to simulate compressible turbulent flows are verified.
Aerodynamic characterization of rolling wheels at high Reynolds numbers
Authors: Duronio Francesco , Di Mascio Andrea
Published: November 2024

Complex and unstable phenomena, such as large-scale boundary layer separations, recirculation zones, and three-dimensional vortical structures, characterize the flow around rotating cylinders. These phenomena are even more interesting when the cylinder is rolling on a solid surface, like a wheel on the ground, because the knowledge of the unsteady features of the wake matters for the aerodynamic design of race cars. For this purpose, we investigated the flow past an isolated wheel in different configurations. We focus on the effect of the aspect ratio and the Reynolds number on the wake for values that reflect the actual operating conditions for a race car. We validated our Detached-Eddy simulation by comparing the results with particle image velocimetry measurements. Then, we analyzed the flow by exploiting proper orthogonal decomposition to identify the turbulence characteristics. The simulation showed excellent agreement with the available experimental data and helped highlight the physics of the wake downstream rolling wheels in different operating conditions.
Numerical study on dynamic performance of a ducted fan moving in proximity to ground and ceiling
Authors: Luo Yiwei , He Yuhang , Ai Tianfu , Xu Bin , Qian Yuping , Zhang Yangjun
Published: November 2024

Ducted fans are widely employed in unmanned aerial vehicles (UAVs) for civil and military uses because they offer low noise and high efficiency. However, dynamic motions in close proximity can disrupt the flow patterns and aerodynamic behaviors of ducted fans, posing a significant stability risk. In this research, numerical simulations were performed using the unsteady Reynolds-averaged Navier–Stokes method and dynamic mesh technique to assess the dynamic performance of ducted fans when rising and descending in proximity effects. The findings reveal that, on the one hand, the rising motion enhances ground effects and diminishes ceiling effects. The thrust losses in ground effect can reach up to 80% of the hovering thrust, while the thrust gains in the ceiling effect can decrease to as low as zero as the translational velocity rises from 1 to 8 m/s. Karman vortex streets are observed in the fan wake at high-speed rise. On the other hand, the descending motion enhances both ground and ceiling effects, leading to increased losses and gains in thrust. The maximum changes account for 63% and 165% of the hovering thrust, respectively. Evolving vortex ring structures are observed during descent. These insights are crucial for optimizing ducted-fan aerodynamic designs and enhancing UAV flight control to ensure safe and efficient operations in varying dynamic conditions.
The reconstruction of surface vibrations from near-field acoustic pressure measurements under steady flow
Authors: Valdivia Nicolas P
Published: November 2024

We consider the problem of reconstructing the surface flow vibration in a medium with steady flow from pressure measurements on a nearby surface. Mathematically, the pressure measurements satisfy the harmonic steady-flow wave equation. This work demonstrates that we can represent any solution to the steady-flow equation by a single-layer integral. Using the layer operator reduces the inverse problem to a linear integral equation of the first kind. Moreover, we reduce the problem to the numerical solution of a matrix system by discretizing this integral equation. We will also show that our inverse problem has logarithmic stability, meaning that the matrix system requires numerical regularization methods (like truncated singular value decomposition) for its solution. In addition, we report numerical studies that validate the accuracy of the proposed numerical reconstruction methodology. Finally, we test the proposed reconstruction methodology with quadrupole examples to test the resolution of our reconstruction.
Noncoplanar magnetic structures in Mn4N epitaxial films evaluated by alternating magnetic force microscopy
Authors: Isogami Shinji , Imamura Kosuke , Kuwayama Ryota , Abe Kouta , Ohtake Mitsuru , Makarova Marina , Saito Hitoshi
Published: November 2024

Noncoplanar magnetic structures in the Mn4N epitaxial thin films grown on the 001-oriented MgO and SrTiO3 (STO) substrates were studied, based on the measurements of topological Hall effect (THE) and the observation of magnetic domain nucleation. The typical nucleation diameter of domain was determined using an alternating magnetic force microscope, which proved advantageous for the visualization of the domain with an out-of-plane magnetic component. The nucleation diameter of the domains on the MgO substrate were ∼150 nm for the thickness of 30 nm and ∼110 nm for 10 nm, while ∼130 nm for 30 nm on the STO substrate. The value of THE was one or two orders of magnitude larger than that estimated based on the nucleation diameter, indicating that the existence of a noncoplanar magnetic structure is the primary factor contributing to the THE in the Mn4N films, comparing to the effect from domain nucleation. The noncoplanar magnetic structure was more pronounced with decreasing thickness and substrate-induced strain.
Coverage- and temperature-induced self-metalation of tetraphenyltransdibenzoporphyrin on Cu(111)
Authors: Shaker Majid , Muth Maximilian , Steffen Julien , Ceccatto Dos Santos Alisson , Jaekel Simon , Adhikari Rajan , Gazetas Pascal , Oleszak Christoph , de Siervo Abner , Jux Norbert , Görling Andreas , Lytken Ole , Steinrück Hans-Peter
Published: November 2024

We have investigated the adsorption and self-metalation of free-base tetraphenyltransdibenzoporphyrin (2H-TPtdBP) on Cu(111) as a function of coverage and temperature using scanning tunneling microscopy, x-ray photoelectron spectroscopy, temperature programmed desorption, and density-functional theory calculations. At low coverages (<0.16 molecules nm−2), we observe isolated individual molecules with an inverted conformation and no self-metalation up to 363 K. At higher coverages, both the formation of ordered islands and self-metalation are observed over time already at room temperature, and accelerate upon heating to 363 K. At 423 K, complete self-metalation occurs for all coverages up to the completed first layer. By comparing our results for 2H-TPtdBP to the existing literature on other tetraphenyl-based porphyrins, we demonstrate how adsorption and self-metalation can be tailored by the choice of substituents.
Thermodynamics and entropic inference of nanoscale magnetic structures in Gd
Authors: Binek Christian , Abbas Shah Syed Qamar , Balasubramanian Balamurugan
Published: November 2024

A bulk gadolinium (Gd) single crystal exhibits virtually zero remnant magnetization, a common trait among soft uniaxial ferromagnets. This characteristic is reflected in our magnetometry data showing virtually hysteresis free isothermal magnetization loops with large saturation magnetization. The absence of hysteresis allows to model the measured easy axis magnetization as a function of temperature and applied magnetic field, rather than a relation, which permits the application of Maxwell relations from equilibrium thermodynamics. Demagnetization effects broaden the isothermal first-order transition from negative to positive magnetization. By analyzing magnetization data within the coexistence regime, we deduce the isothermal entropy change and the field-induced heat capacity change. Comparing the numerically inferred heat capacity with relaxation calorimetric data confirms the applicability of the Maxwell relation. Analysis of the entropy in the mixed phase region suggests the presence of hitherto unresolved nanoscale magnetic structures in the demagnetized state of Gd. To support this prediction, Monte Carlo simulations of a 3D Ising model with dipolar interactions are performed. Analyzing the cluster size statistics and magnetization from the model provides strong qualitative support of our analytic approach.
Electron inertial effects in the rarefied regime of a direct-current (DC) breakdown
Authors: Mansour A R , Vialetto L , Yamashita Y , Hara K
Published: November 2024

A multi-fluid moment model, a drift-diffusion (DD) model, and a particle-in-cell/Monte Carlo collision (PIC-MCC) model are compared to investigate direct-current breakdown accounting only for singly charged ions and electrons. The key difference between the moment and DD models is that the electron inertial terms are taken into account in the moment model while the DD models neglect the inertia terms. The breakdown voltage results obtained from the multi-fluid moment and PIC-MCC models are in good agreement with each other over a wide range of pd values, where p is the gas pressure and d is the distance between the cathode and anode. The steady-state electron momentum balance reveals the importance of the electron inertial term at low values of pd, showing the invalidity of the DD approximation under such conditions. The results also show that the main electron energy loss mechanism transitions from volumetric (collisional) losses at high pd regime, which corresponds to low reduced electric field, to convective heat to the anode at low pd regime, where the reduced electric field is high.
ZnMnCoS/rGO nanocomposite for an effective bifunctional electrode for overall water splitting and supercapacitor applications
Authors: Manikandan M , Karthigeyan K A , Papanasam E , Manikandan E
Published: November 2024

Future energy storage and energy conversion devices will benefit from the development of active electrode materials that serve as both an electrocatalysts and an energy storage device. Recently, mixed metal sulfides are cheaper and have improved electrical and electrochemical performance than their oxide/hydroxide similarly has garnered a lot of interest for use in energy storage and electro catalysis applications. In this, mixed metal sulfides, as zinc manganese cobalt sulfide (ZMCS) and reduced graphene oxide composite zinc manganese cobalt sulfide (rZMCS) were successfully synthesized via hydrothermal route for overall water splitting and supercapacitor. The prepared materials are characterized through x-ray diffraction, x-ray photoelectron spectroscopy, Field emission scanning electron microscope, transmission electron microscope with elemental mapping and Brunauer–Emmett–Teller analysis. The ZMCS and rZMCS electrodes exhibit an over-potential of 258 and 170 mV for HER and 302 and 230 mV for OER at a density of current is 10 mA cm2 in 3 M KOH. Overall water splitting is carried out for rZMCS electrodes and it shows the long-term stability of 15 hrs. The specific capacitances of ZMCS and rZMCS electrodes are 1065 F g1 and 1167 F g1 at 1 A g1. The obtained electrode could maintain 96 % and 98 % until 5000 cycles. Asymmetric supercapacitor device rZMCS//rGO delivers a total amount of energy and power is 47.6 Wh kg1 and 925 W kg1 with could maintain 86 % upto 10000 cycles. The outcomes draw attention to the produced electrode able to be practical as a multifunctional electrode for energy storage and conversion devices.
The Effect of minimal length to the performance of quantum heat engine with Morse oscillator
Authors: Sukamto Heru , Yuwana Lila , Anang Subagyo Bintoro , Purwanto Agus , Taufiqi Muhammad , Latifah Eny
Published: November 2024

The impact of minimal length on the performance of a quantum heat engine based on a harmonic oscillator with a Morse potential is examined, using a diatomic molecule as the working substance. The calculation method employs a frequency analog to the inverse potential width, enabling the determination of heat and work for the harmonic oscillator system similarly to a particle confined in a one-dimensional box. A Carnot-like cycle, comprising two isoenergetic and two adiabatic processes, is utilized. Efficiency and power output are evaluated, taking into account heat leakage. The findings reveal that minimal length enhances efficiency and power output at high oscillation frequencies, with the increasing frequency expanding the engine’s optimal operational range.
Reconfigurable logic-in-memory circuits with ferroelectric nanosheet field-effect transistors
Authors: Cheng Tian-Tong , Li Jia-Cheng , Yang Yu-Xi , Li Qiang , Hsu Hsiao-Hsuan , Zheng Zhi-Wei
Published: November 2024

To accommodate the requirements of small device dimensions and the application of ferroelectric field-effect transistors (FeFETs) in logic-in-memory circuits, we realize the reconfigurable logic-in-memory circuits with ferroelectric nanosheet field-effect transistors (FeNSFETs) through simulation. By evaluating the memory window and logic performances of the devices, it is demonstrated that the key to constructing logical functions are the magnitudes of the drain current at program (PGM) and erase (ERS) state when V
G = 0 V. We find that appropriately increasing the number of nanosheets can enhance the current at PGM state, and appropriately increasing the write voltage can decrease the current at ERS state, which are both beneficial for the achievement of reconfigurable circuits. Thus, it is necessary to take into consideration the trade-offs between the process complexity, power consumption, and logical function realization. This work contributes to the prospective design for ferroelectric reconfigurable logic-in-memory circuits.
Size-dependent thermoelastic damping model for vibrating circular cross-sectional micro/nanobeams according to Moore-Gibson-Thompson thermoelasticity theory
Authors: Widatalla Sabir
Published: November 2024

Motivated by the limitations of classical models in capturing the behavior of materials at the micro/nanoscales, this work proposes an analytical formulation for thermoelastic damping (TED) in circular cross-sectional micro/nanobeams with size-dependent mechanics and heat transfer. This model incorporates small-scale effect through the modified couple stress theory (MCST) for mechanics and the Moore-Gibson-Thompson (MGT) model for heat conduction. To accomplish this objective, the initial step involves introducing the general equations of the MCST and MGT model. Following the establishment of the MGT model, the temperature variations throughout the beam are obtained by solving the heat equation. Additionally, by implementing the principles of the MCST, the model incorporates size-dependent constitutive relations. Finally, the research employs the energy dissipation (ED) approach to render a mathematical expression for TED in tiny beams with circular cross section. This relation, expressed as an infinite series, accounts for size-dependent effects by incorporating the MCST and MGT model. In the section dedicated to numerical results, the initial step involves verifying the accuracy of the proposed model through a validation study. Next, the section showcases various numerical results, focusing on how the MCST and MGT model affect the temperature distribution and TED value. The acquired results underscore that the influence of the MCST and MGT model on the amount of TED in small-sized circular cross-sectional beams cannot be disregarded.