bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimal flow unit of wall-bounded high-pressure transcritical turbulence
Authors: El Mansy Reda , Monteiro Carlos , Mellibovsky Fernando , Jofre Lluís
Published: December 2024

The minimum domain size required to maintain fully developed wall-bounded turbulent flow in high-pressure transcritical regimes is analyzed using direct numerical simulations. The computations involve carbon dioxide at supercritical conditions with pressure P/Pc=2 (subscript c denotes critical value), confined between cold (temperature T/Tc=0.85) and hot (T/Tc=1.5) isothermal walls. The corresponding friction Reynolds numbers are Reτ≈76 and 123 for the cold and hot walls, respectively. The study considers a large baseline domain of size Lx/δ=4π, Ly/δ=2, and Lz/δ=(8/3)π in the streamwise, wall-normal, and spanwise directions, respectively, with δ the half-channel height, as well as truncated setups along the streamwise and/or spanwise directions. The results show that rather small domains are sufficient to reproduce near-wall flow motions, while larger domains are needed to properly capture large-scale structures, especially within the log-law region. Additionally, the study confirms that the distance over which thermal interactions occur is shorter than the typical size of hydrodynamic structures, particularly so in the spanwise direction. This finding suggests that the minimum periodic domain size required in the high-pressure transcritical regime is comparable to that of the minimum flow unit established by other researchers for wall-bounded flows under standard pressure-temperature conditions.
Intelligent optimization of thermal performance in nanoparticle-enhanced enclosures with sinusoidal heating and magnetic field interaction using Multi Expression Programming
Authors: Ullah Naeem , Bibi Aneela , Lu Dianchen
Published: December 2024

This study advances a comprehensive numerical analysis aimed at enhancing thermal transfer within square enclosures filled with water-based oxide nanoparticle suspensions subjected to central sinusoidal heating. Central to this research is the integration of Multi Expression Programming (MEP) for the predictive optimization of thermal efficiency, taking into account the intricate effects of sinusoidal heating geometry, nanoparticles concentration, and an inclined magnetic field. The analysis maintains the initial setup boundary conditions: no-slip at the enclosure walls, isothermal conditions at the left and right walls, and adiabatic conditions at the top and bottom walls, except where sinusoidal heating is applied. Using MEP, these conditions are explored to identify configurations that significantly enhance thermal performance. This method allows for a detailed examination of the impacts of heating element undulation, magnetic field orientation, and nanoparticle dispersion on flow dynamics and thermal transmission. The results emphasize the significant impact of heating element undulation on the heat transfer rate, with MEP predicting optimal undulations that boost thermal efficiency. Furthermore, the strategic application of magnetic fields, as optimized through MEP, facilitates controlled flow distribution and buoyancy effects, with an increased Rayleigh number leading to enhanced convection patterns. The study also delineates the specific boundary conditions under which the Nusselt number, indicative of thermal performance, increases. These MEP-driven insights are invaluable for designing optimized heat transfer systems and energy-efficient applications, establishing a new benchmark for thermal management strategies in practical engineering contexts, firmly rooted in the precision afforded by computational optimization and predictive modeling.
Resolution standards for direct numerical simulation of wall turbulence in high-pressure transcritical fluids
Authors: Monteiro Carlos , Jofre Lluís
Published: December 2024

This study investigates the resolution requirements for direct numerical simulation (DNS) of high-pressure transcritical wall-bounded turbulence, focusing on channel and square duct flow configurations subjected to cold (cw) and hot (hw) walls. The applicability of traditional DNS resolution standards to capture first- and second-order flow statistics is critically assessed, emphasizing the complex thermodynamic and hydrodynamic interactions in transcritical fluid regimes. A comprehensive analysis, incorporating spectrograms, dissipation rate distributions, and distribution of Kolmogorov (ηu), Batchelor (ηT), and density-gradient (δ∇ρ) scales has been conducted. The findings reveal that under-resolved grids significantly underestimate the intensity and proximity of the pseudo-boiling region to the hot wall, particularly in channel flows where lateral confinement is absent. In contrast, square duct flows benefit from secondary flow motions, which stabilize and stratify structures in the pseudo-boiling region. Using “traditionally standard” grid resolutions, first-order velocity and temperature statistics are captured with errors generally below 2%. However, significant discrepancies arise in the turbulent fluctuations, particularly related to energy dissipation for under-resolved cases. To address these issues, the “standard” grid resolution has been refined to better capture local property gradients, their variance, and resulting hydrodynamic and thermophysical scales. For channel flows, the proposed grid features wall-normal resolution requirements of Δyhw+<1 and Δy/ηu, Δy/ηT≲3.5, with streamwise resolutions of Δxcw+≲8, Δxhw+<10.0 and Δx/ηu, Δx/ηT≲9.0. Spanwise resolutions are limited to Δzcw+<2.5, Δzhw+<3.4 and Δz/ηu, Δz/ηu≲3.5. Slightly larger values are applicable for square duct flows. Finally, the resolution requirements obtained are applicable to a wide range of fluids, thermophysical regimes and flow geometries.
Research on mechanical properties and acoustic emission characteristics of sandstone under splitting loading after temperature treatment
Authors: Xiao Weijing , Wan Hongpeng , Zhang Dongming , Huang Yonghu , Liu Kun , Li Shujian
Published: December 2024

In underground engineering, tunnels are important passages for underground wastewater, personnel and vehicles. As the surrounding rock usually experiences the splitting failure, the mechanical properties of the rock subjected to splitting loading are important for surrounding rock stability after a fire. In this study, Brazilian splitting tests were carried out on sandstone after different temperatures (25 °C to 1000 °C), and the acoustic emission (AE) signals of the rock splitting failure process were obtained. Based on the test, the thermal damage rock splitting strength and AE parameters were analyzed, and the effect mechanism of temperature on rock tensile strength was elucidated. The results show that (1) the rock tensile strength fluctuates in the range of 25–400 °C, and the deterioration effect on the tensile strength is significant when the tensile strength exceeds 400 °C. (2) The AE energy follows a power-law distribution, in which the power exponent decreases when it exceeds 400 °C, the main frequency distribution band widens, and the number of AE signals with low energy and high main frequency increases. (3) Mineral decomposition and thermal fracture degrade rock mechanical properties and fracture acoustic signals, resulting in a temperature dependence of rock tensile strength and AE parameters. The research results provide a reference for fracture analysis and stability monitoring of tunnel surrounding rock splitting failure after a fire.
Investigation of geometric morphology and fluid flow characteristics of natural fracture in tight sandstone under non-loading and true triaxial cyclic loading
Authors: Xia Binwei , Peng Jiajun , Wang Lei , Lu Yiyu
Published: December 2024

Understanding the flow characteristics of rock fractures under stress is critical for many geological engineering applications. In this study, flow experiments are conducted on tight sandstone samples with a single natural fracture under true triaxial cyclic loading using the geotechnical consulting and testing systems. The geometric morphology of the fracture is scanned before and after loading using a profilometer. An improved cubic law is developed by including correction factors for stationary roughness, surface tortuosity, and hydraulic tortuosity. The evolution of fracture permeability during cyclic loading of each principal stress is measured using the steady-state method. The results show that (1) the surface tortuosity of the natural fracture correlates as a binary quadratic function with its fractal dimension and joint roughness coefficient. (2) The improved cubic law model has higher accuracy in predicting the permeability of the opening natural fracture than other commonly used modified cubic law models. (3) The principal stresses exhibit an anisotropic influence on fracture permeability. During cyclic loading of principal stress parallel to the fracture, the changes in fracture permeability are neglectable. (4) During cyclic loading of principal stress perpendicular to the fracture, the fracture permeability decreases significantly in the first loading cycle, exhibiting a hysteresis effect. In subsequent cycles, the changes in fracture permeability are nearly reversible, indicating the stress-memory effect of the natural fracture. This study provides direct evidence for the hysteresis and stress-memory effects in the permeability evolution of fractured rock during true triaxial cyclic loading.
Coarse-graining bistability with the Martini force field
Authors: Muratov Alexander D. , Avetisov Vladik A.
Published: December 2024

An increasing interest in molecular structures whose long-term dynamics resemble those of bistable mechanical systems promotes the search of possible candidates that may operate as two-state switching units. Of particular interest are the systems that are capable to exhibit such bistable effects as spontaneous vibrations, stochastic resonance, and spontaneous synchronization. Previously, in all-atom molecular dynamics simulations, it has been demonstrated that short pyridine–furan springs show these bistable phenomena. In this article, we introduce a coarse-grained model of such springs and investigate the possibility to observe the bistability effects, such as spontaneous vibrations. Our findings allow the studies of short pyridine–furan springs at large time and length scales and open field for further computational research of large bistable systems.
Data-driven identification of the critical transition to thermoacoustic instability in a full-scale solid rocket motor
Authors: Xu Guanyu , Wang Bing , Liu Peijin , Guan Yu
Published: December 2024

Thermoacoustic instability is a persistent problem frequently observed in various types of combustors, resulting in damaging consequences. However, our understanding of the dynamics in industrial combustors undergoing thermoacoustic instability, particularly in solid rocket motors, still remains limited. Data-driven precursors for thermoacoustic instability in such systems are also unknown. In this study, we use recurrence network measures and spectral entropy to characterize the dynamics of pressure data obtained from a full-scale solid rocket motor transitioning to thermoacoustic instability and design data-driven precursors for thermoacoustic instability. We show the scale-free nature of combustion noise and that the dynamical transition from combustion noise to thermoacoustic instability can be detected using two complex network measures: the average path length and average betweenness centrality. We calculate the spectral entropy in the frequency domain and find it more sensitive to detecting the dynamical transition and computationally cheap, which is promising for flexible use as a new precursor in thermoacoustic instability prediction. Our work highlights the feasibility of employing complex network measures and spectral entropy for precursors in solid rocket motors, paving a new path for using data-driven measures to early warning of thermoacoustic instability in solid rocket motors.
Numerical simulation of the self-propelled swimming performances and mechanisms of a biomimetic robotic fish with undulating fins under different fin waveforms
Authors: Feng Yikun , Zou Tengan , Xu Xiaojun
Published: December 2024

To study the self-propelled swimming performances and mechanisms of biomimetic robotic fish with undulating fins (BRFUF) under different waveforms, a numerical simulation system coupled with body dynamics and fluid dynamics was established to study the starting, accelerating, and cruising processes of a biomimetic robotic fish in a median/paired fin swimming mode. A systematic parametric study was carried out on the swimming performance of a BRFUF under the cooperative propulsion of two fins, and the mechanism of thrust generation and the influence mechanisms of waveform and kinematic parameters of fins on swimming performance were analyzed based on the hydrodynamic performance, surface pressure distribution, vortex dynamics, and longitudinal velocity iso-surface of the flow field. The results showed that a larger fin ray oscillation angle amplitude increased the acceleration and cruising velocity of the BRFUF from the static state to the cruising stage. A highly concentrated vortex generated at the trough of the fin creates a jet mass that generates a reactive (added-mass) force perpendicular to the propulsive element, which is the mechanism by which the high pressure always covers the trough of the fin. Driven by the flexible fluctuations of the fins, the high-pressure region continuously moves toward the trailing edge along with the vortex. Along with the generation and shedding of the vortex, the high-pressure region is constantly generated, moving and disappearing on the surface of the fin and providing continuous thrust for BRFUF self-propulsion.
High mobility p-channel GaN heterostructures grown by MOCVD through impurity engineering
Authors: Wu Junkang , Yang Xuelin , Song Yingming , Yang Han , Chen Zhenghao , Fu Xingyu , Yang Zhijian , Zhang Shixiong , Shen Bo
Published: December 2024

The p-GaN/AlGaN/GaN heterostructures with integrated n-channel and p-channel have been extensively applied in p-channel field effect transistor (p-FET) devices and complementary (CMOS) logic circuits. However, the hole mobility of the p-channel is still low, especially in the heterostructures grown by metalorganic chemical vapor deposition (MOCVD). In this work, an impurity engineering was designed by introducing Ga vacancies in the p-channel, so that the diffused Mg impurity could substitute the Ga site and form MgGa−1 rather than Mginter+2. The charged impurity scattering was hence suppressed due to the reduction of the impurity charge. As a result, the GaN heterostructure with a hole mobility of 21.8 cm2/V·s with a sheet hole density of 1.02 × 1013/cm2 was realized at room temperature by MOCVD. This work paves a way for improving the transport properties of GaN heterostructures and lays a foundation of high performance GaN-based p-FET devices and CMOS logic circuits on Si substrates.
Unsteady forces on elongated bluff bodies
Authors: Li Shaopeng , Li Zhiyang , Yang Qingshan , Jiang Yan , Wang Yuhang , Huang Hui
Published: December 2024

The aerodynamic shape of the bluff body plays a significant role in determining the unsteady drag force resulting from the three-dimensional (3D) distortion of approaching free-stream turbulence. This paper conducted pressure measurements of bluff bodies with four different cross sections (square, rectangular, circular, elliptic, with different aspect ratio δ = B/D, and B and D are the width and height of the cross section) to study the unsteady aerodynamic behavior of drag force, considering the influence of reduced dimension Lu/D (Lu is the longitudinal integral length scale). Generally, the body with a fixed separation point and a relatively small δ is more blunt, resulting in a higher drag coefficient, spectrum, and coherence than streamlined cross sections in turbulent flow compared to smooth flow. The aerodynamic shape significantly influences the high-frequency component of the one-wavenumber and two-dimensional aerodynamic admittance function (2D AAF). The greater the degree of bluntness of the model, the more pronounced the three-dimensional effect. As Lu/D increases, the drag coefficient and spanwise correlation of the model will both increase and approach the results of a smooth flow. Furthermore, the one-wavenumber AAF and 2D AAF increase at the high-frequency domain, and the 3D effect attenuates. This article proposes a 2D AAF model for modifying the distortion effect in wind tunnel tests.
Synergistic mechanisms of dorsal and anal fins in the C-turn maneuvers of zebrafish
Authors: Li Fei , Liu Yuansen , Yu Yongliang
Published: December 2024

This study aims to provide a deeper understanding of the role of fish fins in the C-turn maneuvers of zebrafish. A three-dimensional geometric model that focuses on detailed modeling of the dorsal and anal fins is constructed using experimental data. Utilizing a self-propulsion computational model, we simulate the dynamics of the zebrafish's C-turn at various turning amplitudes, exploring how the fins interact with water to suppress the lateral flow and enhance the propulsion performance. The results indicate that during small-angle C-turn maneuvers, the anal and dorsal fins increase the maximum and minimum velocities during the bending phase by approximately 10% and 7%, respectively, while the maximum velocity during the recoil phase increases by about 5%. As the turning angle increases, the enhancement effect of the fin propulsion performance diminishes. Furthermore, the synergistic effect of the dorsal and anal fins enhances stability, allowing the fish to complete turns at a relatively stable angular velocity and facilitating “accelerated turning.” This study provides new insights into the adaptive significance of fin structures in nature and their influence on dynamic behavior.
What’s in a name? Why the proposed title change for podiatric surgeons is a step backward
Authors: Gilheany Mark F.
Published: December 2024

The Australian Podiatry Board’s proposal to change the title ‘podiatric surgeon’ to ‘surgical podiatrist’ lacks evidence and is contrary to broader healthcare reform agendas. The current title ‘podiatric surgeon’ reflects scope of practice. Instead of a title change, regulators should focus on removing barriers to effective collaborative care.
Exploring, sampling, and interpreting lunar volatiles in polar cold traps
Authors: Shearer Charles K. , Sharp Zachary D. , Stopar Julie
Published: December 2024

Numerous missions to the Moon have identified and documented volatile deposits associated with permanently shadowed regions. A series of science goals for the Artemis Program is to explore these volatile deposits and return samples to Earth. Volatiles in these reservoirs may consist of a variety of species whose stable isotope characteristics could elucidate both their sources and the processes instrumental in their formation. For example, the δD of potential contributors to the deposits can be used to identify a uniquely light solar wind component. Because of the exceptionally low temperatures of these volatile deposits, examining and interpreting their stable isotope systems to fulfill Artemis science goals through sampling, preserving, curating, and analyzing these samples are far more difficult than for other sample return missions. Collecting and preserving the samples at cryogenic temperatures dramatically increases science yield but is technologically demanding and poses increased risk during transport.
Breathing orchestrates synchronization of sleep oscillations in the human hippocampus
Authors: Sheriff Andrew , Zhou Guangyu , Sagar Vivek , Morgenthaler Justin B. , Cyr Christopher , Hauner Katherina K. , Omidbeigi Mahmoud , Rosenow Joshua M. , Schuele Stephan U. , Lane Gregory , Zelano Christina
Published: December 2024

Nested sleep oscillations, emerging from asynchronous states in coordinated bursts, are critical for memory consolidation. Whether these bursts emerge intrinsically or from an underlying rhythm is unknown. Here, we show a previously undescribed respiratory-driven oscillation in the human hippocampus that couples with cardinal sleep oscillations. Further, breathing promotes nesting of ripples in slow oscillations, together suggesting that respiration acts as an intrinsic rhythm to coordinate synchronization of sleep oscillations, providing a unique framework to characterize sleep-related respiratory and memory processes.
The distinctive mechanical and structural signatures of residual force enhancement in myofibers
Authors: Hessel Anthony L. , Kuehn Michel N. , Palmer Bradley M. , Nissen Devin , Mishra Dhruv , Joumaa Venus , Freundt Johanna K. , Ma Weikang , Nishikawa Kiisa C. , Irving Thomas C. , Linke Wolfgang A.
Published: December 2024

In muscle, titin proteins connect myofilaments together and are thought to be critical for contraction, especially during residual force enhancement (RFE) when steady-state force is elevated after an active stretch. We investigated titin’s function during contraction using small-angle X-ray diffraction to track structural changes before and after 50% titin cleavage and in the RFE-deficient,
mdm
titin mutant. We report that the RFE state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing, most likely caused by elevated titin-based forces. Furthermore, no RFE structural state was detected in
mdm
muscle. We posit that decreased lattice spacing, increased thick filament stiffness, and increased non-cross-bridge forces are the major contributors to RFE. We conclude that titin directly contributes to RFE.
Seagrass ecosystems reduce disease risk and economic loss in marine farming production
Authors: Fiorenza Evan A. , Abu Nur , Feeney William E. , Limbong Steven R. , Freimark Claire B. , Jompa Jamaluddin , Harvell C. Drew , Lamb Joleah B.
Published: December 2024

Seaweed farming comprises over half of global coastal and marine aquaculture production by mass; however, the future of the industry is increasingly threatened by disease outbreaks. Nature-based solutions provided by enhancing functions of coinciding species or ecosystems offer an opportunity to increase yields by reducing disease outbreaks while conserving biodiversity. Seagrass ecosystems can reduce the abundance of marine bacterial pathogens, although it remains unknown whether this service can extend to reducing disease risk in a marine resource. Using a meta-analysis of articles published over the past 40 y, we find that 17 known diseases of seaweeds are attributed to bacteria that have been previously shown to be lower when associated with seagrass ecosystems. Next, we surveyed over 8,000 individual seaweeds among farms in Indonesia and found that disease risk is reduced by 75% when seaweeds are co-cultivated directly within seagrass ecosystems, compared to when seagrass ecosystems were removed. Finally, we estimate that farming seaweed with seagrass ecosystems could increase annual revenue by $292,470 – $1,015,990 USD per km
2
from yield loss due to disease reduction and that ~20.7 million km
2
in 107 countries and 34 territories have suitable environmental conditions for farming seaweeds with seagrass ecosystems. These results highlight the global utility for nature-based solutions as an ecologically and economically sustainable management strategy.
Linguistic complexity development in the writings of Chinese EFL
learners across three proficiency levels
Authors: Wang Zhihong , Yang Lianrui , Chen Ying , Li Xukui
Published: December 2024

This study uses a corpus-based method to analyze the
developmental paths of syntactic and lexical complexity in Chinese EFL learners
across three proficiency levels. It examines six pieces of English essays
written in one semester under school instruction. The goal is to identify both
group results and individual developmental paths. The results show that both
groups and individuals at the same level follow a dynamic, nonlinear development
path, but with different trajectories. The development of syntactic complexity
in their writings is marked by variability and interaction between different
linguistic complexity subsystems. Chinese EFL learners at three proficiency
levels are each in a different stage of L2 development. The study concludes with
important and practical pedagogical implications for L2 instruction.
Falling, slipping, and stumbling backwards
Authors: Jackson Sinéad
Published: December 2024

This paper identifies how experiences of alcohol use disorder (AUD) are metaphorically framed in online alcohol
support materials, using a dataset curated to isolate the language individuals seeking support may encounter. Individuals affected
by AUD face barriers including self-stigma, shame, and a perceived lack of agency, which have been shown to inhibit help-seeking
behaviours. Framings of alcohol use may challenge or reinforce stigmatising perceptions, in ways which may empower or disempower
those affected. There has been little research examining how metaphor is used to communicate perceptions surrounding AUD,
particularly at crucial access points such as the language of support materials. This paper applies the Metaphor Identification
Procedure (Pragglejaz Group, 2007) to identify how metaphor use frames four key aspects
of AUD: lived experience; coping strategies; the disorder; treatment options. The findings show that Journey framings dominate in
this context, highlighting both the long-term nature and potential impermanence of recovery. Individuals are represented with
varying degrees of agency at different stages of dependence, and framings acknowledging mitigated agency tend to anthropomorphise
AUD itself in violent and highly agentive terms. The discussion examines the implications of the identified framings for
support-seeking individuals, highlighting the need for further research exploring how those individuals may respond to and
evaluate these framings.
Claims of not-knowing as patients’ responses in psychodynamic psychotherapy
Authors: Fenner Carolina
Published: December 2024

A fundamental aspect of psychotherapeutic conversation is the joint work of therapist and patient on articulating
something previously hidden or repressed. If the patient refuses to comply with the therapist’s questions or suggestions, such
cooperative work is limited. A possible non-cooperative response by the patient is the claim of not-knowing. This study examines
conversation analytically, using video recordings of German-speaking outpatient psychodynamic psychotherapies, how patients
express two different claims of not-knowing (German ich weiß nicht (‘I don’t know’) and keine
Ahnung (‘no idea’)) as a response to a question. The analysis results in four different functions: refusing
to answer, indexing difficulties, projecting continuation, and
disconfirming, which can only be determined by means of the context and not the structure of ich weiß
nicht or keine Ahnung. Some of the outlined functions might be context-specific for (psychodynamic)
psychotherapy.
Painting lysosomes to study organelle heterogeneity
Authors: Chen Di , Gutierrez Maximiliano G.
Published: December 2024

Like other organelles, the heterogeneity of lysosomes within a single cell has been challenging to capture and study in detail. In this issue, Chen and Gutierrez discuss new work that tackles this question using DNA-PAINT imaging, from Lakadamyali and colleagues (https://doi.org/10.1083/jcb.202403116)
New trends in electromagnetic inverse problems
Authors: Dorn Oliver , Zhong Yu , Lesselier Dominique
Published: December 2024

A special issue has been prepared with the goal to present novel research ideas in the field of electromagnetic inverse problems to a broader interdisciplinary readership. In total, 22 contributions have been accepted to be included in this special issue, covering a broad range of interesting techniques and applications.
A cylindrical microfluidic centrifuge for high-efficient blood separation
Authors: Miao Ying , Shan Liqing
Published: December 2024

In this paper, a new type of microfluidic centrifuge for plasma separation was presented. The main body of the centrifuge is cylindrical, consisting of a sample chamber and two automatic pressure-opening structures, with microchannels spiraling upward along the cylinder. Firstly, Comsol software was adapted to determine the microchannel parameter. The results showed that the centrifugal efficiency (CE) was proportional to the cylinder diameter, the loop number and the rotational speed. Therefore, 2 loops and 30 mm diameter were selected as the structural parameters. Then, polystyrene microspheres were employed to study the centrifuge performance. The experimental results showed that the centrifuge could effectively separate the particles in the suspension, and the centrifuge CE was inversely proportional to the initial concentration and proportional to the outlet ratio. Then, the ability of the centrifuge to separate plasma had been verified by experiments, and when the blood volume was diluted to three times, the CE was 97.4% with the 1:1 outlet ratio. Finally, the centrifuge was compared with other blood centrifuges. It can be seen that the cylindrical centrifuge has the advantages of low cost, simple operation, high separation efficiency, wide sample volume range and high separation rate.
Exploring the focusing system and evaluating structures through proton beam writing
Authors: Mongwaketsi Nametso , Khumalo Zakhelumuzi , Mtshali Christopher , Machethe Katlego , Mokoena Thabang , Barnard Hugo
Published: December 2024

The Tandetron laboratory at iThemba LABS has been performing proton beam writing (PBW) with a beam spot size of approximately 3 × 3 μm2 for the fabrication of microstructures. Successful fabrication of structures measuring about 10–15 μm2 has been achieved. To further optimize the PBW system and enhance the spot size, TRANSPORT measurements were conducted to ensure the feasibility of focusing the beam to less than 1 µm, crucial for achieving high-resolution PBW. Additionally the capabilities of the new PBW in-house developed LabVIEW software to fabricate the ‘sun’ pattern was explored. The TRANSPORT calculations revealed that the quadrupole lenses exhibit a stronger beam focus in the Y axis and a comparatively weaker focus in the X axis. To validate and establish a correlation between the measured spot size of 3.2 μm × 580 nm and its morphology, PBW with raster scanning of the beam over polymethylene methacrylate (PMMA) was performed. Furthermore, the observed PMMA peeling during PBW and identified parameters influencing this behaviour will be considered in future. This research aims to optimize the PBW technique by improving the beam focus and structure resolution.
Orientation dependence of residual current in graphene by few-cycle linearly polarized light
Authors: Zhang Xiaoxue , Zhan Qiang , Liu Chengpu
Published: December 2024

The orientation dependence of residual current in graphene using linearly polarized light is theoretically investigated by numerically solving the time-dependent Schrödinger equation. We find that the residual current exhibits an unexplored small-period sinusoidal modulation in addition to a large-period sinusoidal modulation as a function of polarization angle. Via decomposing the residual current into two components, parallel and perpendicular to the laser polarization direction, we confirm that the large-period modulation comes from the parallel current component, while the small-period modulation is from the perpendicular component. These two current components are both influenced by the asymmetric population distribution as a consequence of the Landau–Zener–Stückelberg interference. The result here demonstrates a strong link between graphene symmetry and residual current and provides some insights into the development of light-field-driven petahertz information technology.
The dynamics of Tonks–Girardeau gas excited by a pulse drive
Authors: Li 李 Jia 佳 , Hao 郝 Yajiang 亚江
Published: December 2024

In this paper we study the dynamics of Tonks–Girardeau (TG) gases in a harmonic potential driven by a Gaussian pulse, which is in correspondence with the excitation dynamics of electrons in matter driven by an ultrashort laser pulse. The evolving dynamics of the TG gas are obtained with a Bose–Fermi mapping method combined with numerical techniques. We calculate the evolving dynamics of the occupation distribution of single-particle energy levels, the density distribution and the momentum distribution of the system. It is shown that the system arrives at a dynamically stable state at the end of driving. In the high-frequency regime, TG gases return back to the ground state, while in the low-frequency regime the population inversion exhibits that all atoms occupy high levels.
Editorial for design of nanocluster-based functional materials
Authors: Wang Guangzhao , Xu Wen Wu , Su Yan , Chen Hongshan , Yuan Hongkuan
Published: December 2024

Ultrasmall nanoparticles, universally recognized as nanoclusters, exhibit distinctive physical and chemical properties that are typically unobservable in bulk materials, stemming from the profound quantum confinement effects. With significant breakthroughs in crystal structure determination and atomically precise synthesis, nanoclusters have garnered increasing attention due to their intriguing luminescence properties, electronic transitions between the highest occupied molecular orbital and lowest unoccupied molecular orbital, chirality, quantized charging capabilities, and magnetic behaviors, along with their promising applications in diverse fields such as energy storage and conversion, catalysis, environmental remediation, and biological medicine. Furthermore, cluster assembly offers a promising route to fabricate innovative materials endowed with captivating properties, thereby offering novel approaches for designing nanocluster-based functional materials. Combining nanoclusters with one-dimensional (1D), two-dimensional (2D), and three-dimensional substrates to form composites usually introduces unusual physicochemical properties that are notably distinct from individual substrates and nanoclusters. Notably, the physicochemical properties of composites constructed from nanoclusters and 1D (or 2D) substrates can be readily tuned by the application of strain or an electric field, offering another additional avenue for designing nanocluster-based functional materials. In the Special Issue of Journal of Physics D: Applied Physics, entitled ‘Design of Nanocluster-Based Functional Materials’, we have compiled a comprehensive collection of 17 articles, showcasing the latest advancements in the field of cluster design and assembly, cluster adsorption and catalysis, and low-dimensional material devices. In the following, we concisely summarize the key research highlights of these studies.
Gallium nitride ultra-wideband terahertz absorber based on periodic pyramidal array
Authors: Qin Mingfei , Ji Shijun , Zhao Ji , Li Jingjin
Published: December 2024

Gallium nitride (GaN) has garnered significant attention due to its unique properties. Here, we present, for the first time, a polarization-independent ultra-wideband absorber in the terahertz band, consisting of a pyramidal GaN array and a GaN substrate. Numerical simulation results indicate that the designed absorber exhibits excellent absorption performance in the range of 0.39–1.98 THz, with a center frequency of 1.185 THz. The relative bandwidth ratio is 134.2%, and the absorption exceeds 90%. The equivalent circuit model further illustrates the ultra-wideband strong absorption characteristics of the proposed absorber. The simulated electromagnetic field distribution indicates that the perfect absorption of the designed absorber is attributed to the excitation of electromagnetic resonance. Additionally, due to the high structural symmetry, the absorber exhibits polarization-independent properties and maintains high absorption performance at large incidence angles. In the future, the proposed absorber will have a wide range of applications in optical applications, including detector devices, light detection equipment and solar energy collection systems.
Investigation of deep trap states at the negative polarization interface of N-polar HEMT through capacitance–conductance measurements
Authors: Lingaparthi R , Lili H , Dharmarasu N , Radhakrishnan K , Zhang J
Published: December 2024

N-polar high electron mobility transistors (HEMTs) will play a crucial role in the future high frequency and high power GaN based technology due to their inherent advantages over Ga-polar technology. However, still, there are some fundamental questions about N-polar technology that need to be addressed. One of the questions that remained unanswered or regaining interest recently is the nature of the negative polarization interface of N-polar HEMTs. Two contradicting views exist regarding the nature of the negative polarization interface at the barrier/buffer interface of N-polar HEMT: one view suggests that hole-like trap states exist at this interface while the other view suggests that two-dimensional hole gas exists at this interface. To give a possible solution to this fundamental question, in this study, two N-polar HEMT heterostructures were investigated, one without any Si δ-doping at the barrier/buffer interface and the other with Si δ-doping at the same interface. Through capacitance–conductance measurements, existence of deep trap states at the negative polarization interface at barrier/buffer interface is demonstrated for the sample without Si δ-doping, which indirectly contradicts the idea of existence of hole gas at this interface. Moreover, in the capacitance–conductance measurements, Si δ-doping is shown to eliminate the presence of deep trap states.
Crossover in atomic mobility underlying the glass transition in inorganic glasses
Authors: Cockrell C , Grimes R W
Published: December 2024

While the glass transition is easy to identify macroscopically, the underlying atomic mechanisms which facilitate the transition from amorphous solid to fluid are still poorly understood. We conduct classical molecular dynamics simulations on a variety of inorganic glasses in order to identify these mechanisms. While also modelling larger systems, we find that the essential qualities which constitute a glass and its transition to a liquid are present even in systems containing only a few hundred atoms. The transition is therefore a local phenomenon. Atomic mobility, the ability of an atom to escape its local coordination environment, is identified as a universal marker of the glass transition. In the solid state, the fraction of mobile atoms is negligible, whereas in the liquid state, effectively all atoms are mobile. The glass transition is continuous between these limiting states, with half of the network forming atoms attaining mobility exactly at the glass transition temperature, over a specific mobility half life, informed by thermodynamics. Over time, network forming atoms which were immobile may swap to become mobile and vice versa, though the population of mobile atoms remains a half.
Assessing radiation exposure of fingers of PET/CT technologists during 18F-FDG procedures using active extremity dosimeters: a single-center study
Authors: Ramanathan Vijitha , Gamage SP , Karunathilaka UIU , Wickramasinghe WMIS , Tudugala Ranga
Published: December 2024

Extremity radiation exposure in nuclear medicine is a growing concern because it may surpass the maximum permissible dose of 500 mSv. This study aimed to assess the occupational finger dose received by technologists during the preparation and administration of 18F-FDG radiopharmaceuticals in positron emission tomography-computed tomography (PET-CT) whole-body scan procedures. Fifty scans were selected, with one procedure excluded due to a high administered activity. The mean administered activity per scan was 207.2 ± 41.8 MBq, with preparation and administration times averaging 1.44 ± 1.30 min and 0.46 ± 0.31 min, respectively. The technologist’s mean total finger dose received during preparation and administration was 253.5 ± 153.3 µSv per procedure. A significant positive correlation was found between the administered activity and occupational dose, with patient’s body mass index, preparation time, and administration time also contributing to dose variation. Based on 703 PET-CT procedures conducted in 2022, the estimated occupational finger dose for a technologist was 178.2 mSv annually. This value is well below the International Commission on Radiological Protection’s maximum permissible dose of 500 mSv. The findings of this study have a significant impact on extremity dosimetry in nuclear medicine in Sri Lanka, as this is the first study of its kind.
A hybrid transformer masked time-domain denoising network for vibration signals
Authors: Huang Xin , Qian Weiwei , Zhang Peng , Ding Zhongtian , Li Shunming
Published: December 2024

Health-condition-sensitive vibration information is prone to be swamped by widespread noise. Denoising is always indispensable, but existing methods still lack adaptability. Therefore, a novel intelligent denoising framework called a hybrid transformer masked time-domain denoising network (HTMTDN) is proposed. First, a dense dilation convolution block and a hybrid transformer are constructed to deal with fault impulse scale variations and unexpected noise frequency bands respectively, which greatly improves the adaptive denoising capability and relieves tough denoising parameter tuning. Further, interpretable time- and frequency-domain joint constraints are constructed to enhance the network’s optimization ability under strong noise. Finally, a novel strategy called overlapping reconstruction is introduced to recover 1D signals from 2D signal segments. Extensive experiments based on two bearing fault datasets with variable loads and rotation speeds confirm the remarkable performance of the HTMTDN under low signalnoise ratios, and present good adaptability in 15 health conditions without separate hyperparameter tuning, which shows promise for real-world applications.
Correlation between the blob properties and global plasma parameters in L-mode on EAST
Authors: Wang P , Hu G H , Chen L , Wang Y F , Shan L L , Jiang X S , Wang L , Xu G S , Yang Q Q , Meng L Y , Lin X , Wang Y B , Wu D G , Yan N , Peng J
Published: December 2024

The correlations between blob properties and plasma density n
e, plasma current I
p, edge safety factor Q
95, toroidal magnetic field B
t, plasma stored energy W
MHD, heating power P
heating, upper triangularity

δ

U

, and the outer midplane gap in the L-mode plasmas on EAST are studied. It was found that the blob size and lifetime exhibit a strong positive correlation with plasma density, toroidal magnetic field, and edge safety factor, and a strong negative correlation with plasma current, heating power, and stored energy. Conversely, the blob detection rate shows essentially the opposite correlations with these parameters. Given that the normalized collisionality parameter Λ is proportional to n
e, B
t, Q
95 and inversely proportional to I
p and T
e, it suggests that the normalized collisionality parameter Λ may play a crucial role in influencing blob size, lifetime, and detection rate. However, the radial velocity of blobs was found to be only negatively correlated with the heating power and independent of other parameters, indicating that it is not only affected by the collisionality Λ. The dependence of blob velocity on the heating power may be related to the effect of the heating power on the E× B flow of the background plasma. In addition, the plasma configuration in the range of this study has no noticeable impact on the blob properties measured in this study.
Enhancement of all-inorganic perovskite solar cell performance through the addition of CuI as a hole transport layer additive
Authors: Wang Xiao , Jia Zelin , Zhang Cui , Liu Bei , Zhou Jinghua , Zhang Qing , Zhang Yu , Wang Donghui , Xue Tao , Guo Kunping , Huang Jin , Zhang Fanghui
Published: December 2024

The transport layer is one of the main factors affecting the stability and efficiency of all-inorganic perovskite solar cells (PSCs). It is still difficult to produce an HTL with the required properties using the present production methods. Based on the solubility, a new porous transport layer of CuI doped on the surface of inorganic perovskite is proposed. CuI inclusion promotes an energy level alignment that reduces ionic loss, inhibits charge carrier recombination, and improves hole extraction efficiency. CuI addition corrects surface imperfections of the perovskite and avoids defects caused by Spiro-OMeTAD pinholes, leading to excellent hole extraction performance and fast hole mobility rates. Due to this adjustment, power conversion efficiency (PCE) is improved by 26%, resulting in an optimized PCE of 12.39%. The filling factor and the short circuit current density (J
sc) were increased to 17.93 mA cm−2 and 0.71, respectively. In addition, the stability of CuI is improved due to the barrier effect of inorganic Cul on air and water entering the perovskite layer. The results show that CuI doped hole transport layer film is a promising method to realize high performance and air-stable PSC.
Optimization of specific on-resistance of a two-zone variational vertical doping superjunction with insulating layers
Authors: Huang Haimeng , Li Wenjun , Xiong Juncheng , Jin Zhenghao , Zhang Zonghao , Cheng Junji , Yi Bo , Yang Hongqiang , Wang Zhiming
Published: December 2024

A novel two-zone variational vertical doping superjunction structure with insulating layers (I-VVDSJ) is proposed. The path length of the impact ionization integral can be shortened by the insertion of a lateral insulator layer. This allows for a higher average doping concentration and a superior specific ON-resistance (R

on,sp

). Two-dimensional electric field (E-field) distributions are unified for the entire structure by utilizing the sign function for optimization of R

on,sp

with MATLAB and MEDICI. Compared with a conventional superjunction structure for breakdown voltage (BV) larger than 700 V, the optimized R

on,sp

(R

on,sp(opt)

) can be reduced by over 27%. Formulae for the design parameters are proposed as a function of BV and aspect ratio (AR). Furthermore,

R

on
,
sp
(
opt
)

=

δ

(
2.278
×

10

−
5

)

AR

−
1.295

BV

2.33

mΩ cm2 is proposed to guide the design for the I-VVDSJ structure with the factor

δ

representing the junction field effect transistor effect.