bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray transition and K-edge energies in dense finite-temperature plasmas: Challenges of a generalized approach with spectroscopic precision
Authors: Li X. , Rosmej F. B.
Published: January 2025

The capacity to predict X-ray transition and K-edge energies in dense finite-temperature plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions. The dual characteristics of bound and continuum states in dense matter are modeled by a valence-band-like structure in a generalized ion-sphere approach with states that are either bound, free, or mixed. The self-consistent combination of this model with the Dirac wave equations of multielectron bound states allows one to fully respect the Pauli principle and to take into account the exact nonlocal exchange terms. The generalized method allows very high precision without implication of calibration shifts and scaling parameters and therefore has predictive power. This leads to new insights in the analysis of various data. The simple ionization model representing the K-edge is generalized to excitation–ionization phenomena resulting in an advanced interpretation of ionization depression data in near-solid-density plasmas. The model predicts scaling relations along the isoelectronic sequences and the existence of bound M-states that are in excellent agreement with experimental data, whereas other methods have failed. The application to unexplained data from compound materials also gives good agreement without the need to invoke any additional assumptions in the generalized model, whereas other methods have lacked consistency.
Limits of spectral measures for linearly bounded and for Poisson distributed random potentials
Authors: Hasler David , Koberstein Jannis
Published: January 2025

We show the existence of infinite volume limits of resolvents and spectral measures for a class of Schrödinger operators with linearly bounded potentials. We then apply this result to Schrödinger operators with a Poisson distributed random potential.
Range and accuracy of in-plane anisotropic thermal conductivity measurement using the laser-based Ångstrom method
Authors: Gaitonde Aalok U. , Weibel Justin A. , Marconnet Amy M.
Published: January 2025

High heat fluxes in electronic devices must be effectively dissipated to prevent local hotspots, which are critical for long-term device reliability. In particular, advanced semiconductor packaging trends toward thin form factor products increase the need for understanding and improving in-plane conduction heat spreading in anisotropic materials. The 2D laser-based Ångstrom method, an extension of traditional Ångstrom and lock-in thermography techniques, measures in-plane thermal properties of anisotropic sheet-like materials. This method uses non-contact infrared temperature mapping to measure the thermal response to periodic laser heating at the center of a suspended sample. The spatiotemporal temperature data are analyzed via an inverse fitting algorithm to extract thermal conductivities in the in-plane orthotropic directions that best adhere to the governing heat conduction equation. Using this algorithm, we present an approach to simultaneously fit data across multiple heating frequencies, which improves measurement sensitivity because the thermal penetration depth varies with frequency. The accuracy of this technique is assessed by tuning experimental parameters such as sample dimensions and heating frequency. A standardized workflow is proposed for measuring unknown materials and for processing the data, including filtering out regions influenced by laser absorption and heat sink boundary effects. Numerical simulations validate the method across a wide range of thermal conductivities (0.1–1000 W m−1 K−1) and material thicknesses (0.1–10 mm), with accuracy demonstrated for anisotropy ratios up to 1000:1. Experimental measurements on isotropic and anisotropic materials agree well with the benchmark values. Ultimately, standardization of this technique supports the development of engineered anisotropic heat-spreading materials for thermal management and packaging applications.
Canal site photovoltaic: Performance analysis using experimentally characterized microclimate prediction, and optimized PV thermo-electric models for hot semi-arid climate
Authors: Safdar Nouman , Butt Arslan Dawood , Farhan Muhammad , Bhatti Abdul Rauf , Qasim Mirza Hussain Raza
Published: January 2025

Photovoltaic (PV) system installation on freshwater bodies like canals, instead of on-land installation, can help preserve valuable land. Canal site microclimate can induce localized cooling, which improves PV performance due to a reduced solar cell temperature (Tcell). This impact has been studied in the literature using mostly ex-situ experimental setups that approximate the canal site microclimate using water tanks. This work presents an alternative approach where a robust microclimate prediction model is developed based on standalone measurements in a hot semi-arid climate. This model evaluates canal-site ambient conditions for different regions, climates, and months characterized by the land-site ambient temperature (Tamb) and relative humidity (RH) levels between 13.5–46.3 °C and 12%–76% respectively. The corresponding land-site specific humidity (SH) range is 4.95–15.73 g/kg. This prediction model is later used with an optimized three-dimensional distributed steady-state (3DDSS) PV model to analyze the annual performance of canal- and land-site PV using thermo-electric simulations. With a single 670 W commercial PV panel, an annual increase in 1.52% in the electrical energy generation with a Tcell reduction of 4.52 °C is obtained for the Rakh Branch canal site, Pakistan. In situ experimental measurements have also been performed with a scaled-down PV setup, which supports these results. This work provides mathematical models for researchers to use in conjunction with public ambient condition databases to estimate microclimate conditions over small freshwater bodies. It also acts as a guideline for consumers and public policymakers to evaluate the potential of canal site PV systems accurately.
Acoustic resonant hydrogen leak detection for hydrogen production by water electrolysis
Authors: Wang Jianwei , Wang Huili , Wang Xueyuan
Published: January 2025

A non-invasive hydrogen leak sensor based on acoustic resonant frequency measurement using the fast Fourier transform is developed. The sensitivity of the resonant frequency to hydrogen concentration variation of the acoustic resonator is utilized. The acoustic resonator has been optimized through finite element method analysis to meet the requirements of the measurement application. Under the premise of fully considering the frequency response, detection time, and related metrological characteristics, the excitation and detection circuit based on a STM32 microprocessor was designed. To reduce the influence of temperature on measurement results, a double resonator structure is adopted. The overall sensor design is made up of low-cost, simplicity, and commercially available components. The experimental results show that the sensitivity limit is 33.6 ppm and an upper dynamic range of 100%. The presence of hydrogen can be quickly detected within 5 s. It can fulfill the requirements for detecting high concentration hydrogen leakage and provide monitoring data for the safe operation of the hydrogen production system.
BEOL-compatible Te-TeOx p-FETs with channel length down to 50 nm at cryogenic temperatures
Authors: Xu Ying , Sun Yiyuan , Zheng Zijie , Wang Yuxuan , Kang Yuye , Han Kaizhen , Chen Xuanqi , Zheng Gerui , Gong Xiao
Published: January 2025

In this work, we present p-type Te-TeOx FETs with BEOL-compatibility targeting high-performance computing at cryogenic temperatures. The devices feature aggressively scaled channel lengths (Lch of 50 nm) deposited using the sputtering method that is cost-effective, large-scale manufacturable, and highly controllable. We investigated the effects of oxygen content and film thickness in the sputtered channel layer on device performance. The device achieves a maximum transconductance (Gm, max) of 142 μS/μm, an on/off ratio exceeding 3 × 108, a subthreshold swing (SS) of 99 mV/Dec., a high hole mobility of 28.6 cm2/V s, and excellent NBTI and PBTI reliability characteristics at 77 K.
Near-infrared photoluminescence from bismuth, a deep defect in cesium lead bromide perovskite
Authors: Brittman Sarah , Jones Brendon T. , Stewart Michael H. , Marcheschi Barbara A. , Cunningham Paul D. , Proscia Nicholas V. , Ellis Chase T. , Murphy John P. , Sendgikoski Kyle , Brintlinger Todd H. , Lyons John L.
Published: January 2025

Bismuth has been investigated as a potential n-type dopant in hybrid lead halide perovskites, but its behavior in all-inorganic perovskites such as CsPbBr3 has not been thoroughly characterized. We show that Bi behaves as a deep defect in CsPbBr3 and gives rise to broad near-infrared emission, similar to its behavior in hybrid perovskites, but a phenomenon not previously reported in CsPbBr3. Using inverse temperature crystallization, we synthesized a series of Bi-doped CsPbBr3 crystals and quantified their Bi concentrations by inductively coupled plasma optical emission spectroscopy. Bi incorporation redshifted the absorption edge, and hybrid density functional theory calculations show that this increased absorption comes from excitation into the deep donor level of Bi, not from narrowing of the bandgap of CsPbBr3. All Bi-doped crystals emitted both narrow band-edge (2.37 eV) and broad defect-level (1.16 eV) photoluminescence, consistent with our theoretical prediction. Time-resolved photoluminescence measurements indicate that Bi incorporation decreases the lifetime of the band-edge emission and gives rise to long-lived defect emission. Power-dependent photoluminescence measurements conducted at 14 K show that the band-edge peak intensity scales as expected for a free or bound exciton, while the sublinear scaling of the infrared defect peak is consistent with recombination between a free hole and a trapped electron, as proposed by theory. These results demonstrate the quantitative accuracy with which current theoretical approaches predict defect behavior in halide perovskites; such theory is key to guiding the experimental development of doping in these materials.
Effect of different loading distribution forms on the energy characteristics of mixed-flow pumps
Authors: Wang Mengcheng , Ding Zheng , Lu Jiaxing , Shi Lei , Chen Jiaqi , Yang Yang , Gu Yandong , Zhang Fan
Published: January 2025

Loading distribution significantly affects the flow field in the impeller channel, but research on the effects of different loading distribution forms on the performance of mixed-flow pumps is relatively scarce. In this study, three typical mixed-flow pump models, namely front-loading model (FLM), middle-loading model (MLM), and back-loading model (BLM), were designed by changing the loading distribution at the shroud using the inverse design method. The energy losses within the three models were analyzed quantitatively and visually using the entropy generation method. The results show that using front-loading, middle-loading, and back-loading in the design of mixed-flow pumps improves efficiency under common, low, and high flow rate conditions, respectively; in particular, the efficiencies of the FLM, MLM, and BLM under design conditions were 88.72%, 87.82%, and 87.01%, respectively. The entropy generation analysis indicates that the loading distribution has a minor influence on the energy loss within the impeller, but its influence on the energy loss in the downstream components of the impeller can exceed 30%. Internal flow analysis shows that the effect of loading distribution on the relative velocity and adverse pressure gradient at the impeller outlet is the primary reason for the change in the performance of mixed-flow pumps.
Band structure engineering in 2D BA2PbI4/InSe perovskite heterostructures and superlattices
Authors: Gao Yujia , Huang Tengcheng , Wu Zhuxia , Shi Tingting , Xie Weiguang
Published: January 2025

Periodic stacking of two van der Waals materials enables the realization of superlattice structures with artificial design of band structure. Two-dimensional perovskites offer structural flexibility for engineering of band structure that can result in superlattice structures. Here, InSe/BA2PbI4 perovskite heterostructure and superlattice are explored by first principles calculation. Both the heterostructure and superlattice show a similar direct bandgap structure. As the concentration of VBA defects increases, the bandgap of the heterostructure and superlattices generally increase in different manners due to different interfacial interaction. The introduction of VI defects leads to the formation of a type-I band alignment, contrasting with the type-II band alignment resulting from VBA defects. These findings offer valuable insights into the defect-driven modulation of electronic properties in semiconductor superlattices and heterostructures, providing opportunities to tailor them for various optoelectronic applications.
Higher-order topological fermion phase and Weyl phonon phase in Li-intercalated graphene layers
Authors: P. C. Sreeparvathy , Huang Zhi-Quan , Villaos Rovi Angelo B. , Chuang Feng-Chuan
Published: January 2025

Two-dimensional (2D) higher-order topological fermionic phases coexisting with intriguing topological phonon states have recently become a focal point of condensed matter research. However, the coexistence of the second-order topological phase and valley Weyl phonon features in 2D materials remains unexplored. In this Letter, we present a two-dimensional Li-intercalated graphene material family that serves as an ideal platform for demonstrating the coexistence of topological electron and phonon features. Our study, which utilizes first-principles calculations, investigates the structural, electronic, and topological properties of several Li-intercalated graphene materials. The higher-order topological phases are protected by C6 rotation and inversion symmetries in Li-C6 and Li-C6-Li layers, respectively, as confirmed by their calculated topological invariants (χ6, Z4). Topologically protected corner modes are noticed within the gapped bulk and edge states (in the armchair edge) in the nanoflake geometry of the Li-C6 compound. Notably, the phonon spectra of the Li-C6 and Li-C6-Li materials exhibit Weyl phonon nodes in the Brillouin zone where the phonon bands touch at the valley-high symmetry point. The presence of localized Berry curvature and robust topological phonon edge states further confirms the existence of Weyl phonon nodes in these materials. Our first-principles study predicts potential candidates for hosting the coexisting electronic and phononic features and highlights the technological aspects of Li-intercalated graphene materials.
Linear stability analysis of Navier–Stokes–Voigt fluid with slip boundary condition in a porous medium
Authors: Arjun C. M. , Praveena M. M. , Shashi Prabha Gogate S.
Published: January 2025

We study the instability of plane Poiseuille flow of viscoelastic Navier–Stokes–Voigt fluid in a homogeneous porous medium. The pressure gradient drives the viscoelastic fluid between two parallel plates. The effects of Voigt parameter Λ, permeability M, and slip length(s) l on one wall (asymmetric) and on both walls (symmetric) on the flow stability are analyzed by obtaining the numerical solution of the generalized eigenvalue problem using the Chebyshev spectral collocation method that gives the precise upper bound for stability. The plane Poiseuille flow of Navier–Stokes–Voigt fluid becomes stable for increasing slip length l, which preserves the Newtonian eigenspectrum up to a certain range of Λ, M, and l for both the symmetric and asymmetric flows. The eigenspectra of the flow exhibit that the unstable mode always appears on the wall mode for a certain range of Λ, M, and l, and upon an increase in these values, the same unstable mode is seen to become stable. The neutral stability curves that correspond to various values of Λ,M, and l are found to be an extension of the Tollmien–Schlichting instability that is noticed for the Newtonian channel flow. The energy budget method is used to further confirm our prior findings by quantifying the physical mechanisms behind occurrence of instability. The negative energy production caused by Reynold's stress is mainly responsible for stabilization as contributions from viscous dissipation, viscoelastic fluid, and porous medium are positive across the channel. Other mechanisms that contribute to the flow stability are also examined.
Investigations of key issues on the reproducibility of high-T
c superconductivity emerging from compressed La3Ni2O7
Authors: Zhou Yazhou , Guo Jing , Cai Shu , Sun Hualei , Li Chengyu , Zhao Jinyu , Wang Pengyu , Han Jinyu , Chen Xintian , Chen Yongjin , Wu Qi , Ding Yang , Xiang Tao , Mao Ho-kwang , Sun Liling
Published: January 2025

Signatures of superconductivity near 80 K have recently been discovered in single crystals of La3Ni2O7 under pressure, which makes it a new candidate for high-temperature superconductors dominated by 3d transition elements, following the cuprate and iron-pnictide superconductors. However, there are several critical questions that have been perplexing the scientific community: (1) What factors contribute to the inconsistent reproducibility of the experimental results? (2) What is the fundamental nature of pressure-induced superconductivity: bulk or nonbulk (filamentary-like)? (3) Where is the superconducting phase located within the sample if it is filamentary-like? (4) Is the oxygen content important for the development and stabilization of superconductivity? In this study, we employ comprehensive high-pressure techniques to address these questions. Through our modulated ac susceptibility measurements, we are the first to find that the superconductivity in this nickelate is filamentary-like. Our scanning transmission electron microscopy investigations suggest that the filamentary-like superconductivity most likely emerges at the interface between La3Ni2O7 and La4Ni3O10 phases. By tuning the oxygen content of polycrystalline La3Ni2O7, we also find that it plays vital role in the development and stabilization of superconductivity in this material. The upper and lower bounds on the oxygen content are 7.35 and 6.89, respectively. Our results provide not only new insights into the puzzling issues regarding this material, but also significant information that will enable a better understanding of its superconductivity.
Impact of human intervention and predator–prey dynamics on ecosystem virus transmission
Authors: Zhai Shidong , Zhang Jiyu , Tang Yuhan , Ma Jun
Published: January 2025

Humans and predators occupy dominant positions in ecosystems and are generally believed to play a decisive role in maintaining ecosystem stability, particularly in the context of virus transmission. However, this may not always be the case. By establishing some ecosystem virus transmission models that cover both human perspectives and predators, we have drawn the following conclusions: (1) Controlling vaccination activities from the human perspective can potentially lower the transmission rate and improve herd immunity, thereby indirectly protecting unvaccinated risk groups. (2) In the ecosystem, the human perspective does not always determine the spread of viruses. Once the ecological balance between predators and prey is disrupted, there may be scenarios where predator populations die out, prey populations overpopulate, or both predators and prey go extinct. In such cases, the spread of the virus has little impact, and the system cannot restore itself to a new equilibrium state. In this case, even if humans intervene, it is difficult to change the fate of species extinction. (3) In situations where predator and prey populations maintain a stable state, human attitudes and actions are particularly critical. Human intervention can directly affect the transmission rate of the virus and the recovery rate of hosts, thereby rapidly reducing the infection rate and mitigating the harm caused by the virus. If humans do not intervene, predators may remain infected for a long time, thereby posing a serious threat to the ecosystem.
Theoretical studies of transient hydrodynamic phonon transport in two-dimensional disk geometry
Authors: Zhang Chuang , Wu Lei
Published: January 2025

Many phonon hydrodynamics phenomena, including heat vortices, wave and parabolic distributions of heat flux, which appear due to sufficient normal process, can also appear when there is insufficient normal process. In other words, a smoking gun of phonon hydrodynamics phenomena at the macroscopic level is still lacking. To find it, transient cooling phenomenon in two-dimensional materials is studied based on the phonon Boltzmann transport equation. A heating pulsed Gaussian laser beam is added at the center of two-dimensional disk and it continues to heat the system for a while under the environment temperature. After the heating laser is removed, results show that the transient temperature could be lower than the environment temperature and this phenomenon could only appear with sufficient normal process and insufficient resistive process, which is exactly a smoking gun of phonon hydrodynamics. In addition, the possibility of this phenomenon measured by transient Raman experiments is theoretically discussed. Numerical results show that given a single-layer suspended graphene disk sample with diameter 7 μm, this transient cooling phenomenon can appear in the temperature range of 50–150 K.
Improving the thermal performance of a spherical latent thermal energy storage using innovative fins and porous media
Authors: Amini Yasser , Hekmat Farhan
Published: January 2025

The performance of latent heat thermal energy storage (LHTES) systems can be significantly enhanced by improving the thermal properties of phase change materials (PCMs). Today, these systems serve as a sustainable energy resource and find applications in various sectors, including energy conservation in buildings, household hot water systems, air conditioning units, peak load reduction, waste heat recovery, and biomedical applications. This paper investigates the effects of fins and metal foam on the melting and solidification rates of PCM within a spherical latent heat thermal energy storage unit (LHTESU). To assess the impact of fin geometry on energy storage efficiency, three types of fins were tested: fins with a constant length, fins with a variable length, and curved-shaped fins. Additionally, three different porosity levels of metal foam were considered. A finless reservoir filled with PCM was used as a baseline and benchmark to evaluate the performance enhancements provided by the different fin and metal foam configurations. The results indicated that utilizing seven fixed-length fins with a thickness of 1 mm represents the most effective configuration for increasing melting and solidification rates among the constant volume fraction cases, leading to reductions in melting and solidification times by 58.76% and 72.66%, respectively. Furthermore, incorporating metal foam significantly improved the phase change rate of the PCM, achieving reductions in melting time by 89.11% and solidification time by 94.96% when 85% porosity was used. These results highlight the potential of advanced fin designs and porous media in significantly enhancing the thermal energy storage efficiency, offering promising insights for future sustainable energy technologies.
Lagrangian analysis on mechanism of forced convection heat transfer control for cylinder via deep reinforcement learning
Authors: Liu Yangwei , Wang Feitong , Zhao Shihang , Hou Jiexuan
Published: January 2025

Forced convection heat transfer plays a vital role in engineering; however, its control presents significant complexity. In this paper, a closed-loop deep reinforcement learning framework is introduced to optimize cooling tasks in a heat exchanger, where a cylindrical heat source is immersed in a narrow cavity. The online learning deep Q-networks (DQN) algorithm is implemented, and an offline learning conservative Q-learning soft actor-critic (CQL-SAC) algorithm is first proposed to learn based solely on preexisting databases without interacting with the environment. Taking the continuous blowing mode as the baseline, the CQL-SAC control obtains a temperature reduction of 49.1% greater than that under the optimal human control and consumes only 0.53% of the time required by online learning. While the DQN control achieves the best cooling performance, with a temperature reduction exceeding that of the optimal human control by 91.4%. The underlying mechanisms are analyzed. Particle tracking technology and Lagrangian coherence structures (LCS) are employed to identify regions of sufficient heat exchange and precisely map from where a cold particle can be captured to undergo sufficient heat exchange or swiftly escapes with inadequate heat exchange. The mechanism of the enhanced cooling effect under the DQN control is clarified from a particle capturing and escaping perspective. The greater overlap between the cold particle capture region and hotspots correlating with the more saddle points of the LCS within this region indicates more intense heat exchange in areas closer to hotspots, thus resulting in better cooling performance.
A 780 nm optical frequency standard based on diffuse laser cooled 87Rb atoms
Authors: Guan Xiaolei , Zhang Jia , Gao Xun , Wang Yu , Shi Tiantian , Chen Jingbiao
Published: January 2025

We demonstrate an optical frequency standard by locking the output frequency of an external cavity diode laser to the 780 nm D2 transition of diffuse laser cooled 87Rb atoms using frequency modulation spectroscopy (FMS). A 50-cm-long cold atomic cloud is obtained within a ϕ 2 cm ×l 50 cm vacuum glass tube, featuring greater simplicity and reliability. By analyzing the impact of power and detuning of cooling and repumping lasers, and power of frequency-modulated laser on FMS based on cold atoms, we choose the optimal parameter and lock the laser frequency to the 87Rb 52S1/2 (F = 2) → 52P3/2 (F′ = 3) cycling transition. The cold-atom-based optical frequency standard achieves an in-loop frequency stability of 3.3 × 10−15 at 1 s, with peak-to-peak frequency fluctuations being less than 50 Hz within 6000 s. This represents the integration of cold atoms into an optical frequency standard utilizing FMS for frequency stabilization. In contrast to the common cold-atom optical frequency standards, our approach requires fewer lasers and eliminates the need for a complex and expensive Pound–Drever–Hall (PDH) system. Its low complexity makes it a promising candidate for development into a space cold-atom clock, promoting advancements in space science and navigational positioning. Additionally, it possesses great potential to serve as an absolute wavelength standard.
Exact solution for laminar viscous fluid flow over a contaminated liquid drop placed in a porous region: Magnetohydrodynamics
Authors: Jammula Sivaprasad , Meduri Phani Kumar
Published: January 2025

A uniform, steady, viscous, laminar magnetohydrodynamic (MHD) flow over a fixed partially contaminated liquid drop placed in a porous region is considered. An interfacial slip is assumed on its surface. The drag force with cap angle is obtained analytically. The special case results are consistent with available results in literature. The flow pattern graphs are studied. It is observed that the coefficient of drag values rise in tandem with increases in the slip parameter, viscosity ratio, Hartmann number, and porosity parameter. Compared to viscous flow over a contaminated liquid drop and MHD flow over a contaminated liquid drop without being placed in a porous region, the drag of MHD flow over a contaminated liquid drop planted in a porous region is greater. It can be seen from the flow pattern comparison graph that areas without porous media have free flow, but areas with porous media have enhanced internal circulations and external flow that is extended toward objects.
Structural and hydrodynamic characteristics of hollow cylinder during high-speed water entry
Authors: Xia Shengsheng , Wei Yingjie , Wang Cong , Sun Tiezhi , Yang Liu , Lu Jiaxing
Published: January 2025

The hollow cylinder is a special cylindrical body with a through structure in the middle position. A collaborative method based on the finite volume method and the finite element method is used to numerically calculate high-speed vertical water entry of the hollow cylinder. The results show that the hollow cylinder exhibits a unique internal jet phenomenon, and the height of the jet shows an almost linear growth trend. Compared to the completely sealed hollow cylinder, the displacement and velocity of the hollow cylinder after entering into water are greater, but the volume of generated cavities is smaller. The force and stress at the bottom of the hollow cylinder are smaller than those at the bottom of the completely sealed hollow cylinder. The force and stress at the bottom of the hollow cylinder are greater than those at its top position. The greater thickness of the hollow cylinder has greater velocity and displacement, as well as greater peak values of the force and stress at its bottom position. The stress fluctuation at the bottom of the hollow cylinder with a smaller thickness is more pronounced.
Effects of surface morphologies on boiling heat transfer in droplet impingement on superheated surfaces
Authors: Ibrahim Mohammed , Aref Omar , Zhang Chuangde , Rajamuni Methma , Chen Li , Young John , Tian Fang-Bao
Published: January 2025

A phase change spray cooling system is an important engineering application of droplet impingement on superheated surfaces. This work studies the impacts of different morphologies on boiling heat transfer during droplet impingement on superheated surfaces using a three-dimensional hybrid approach: the multiphase pseudopotential lattice Boltzmann method for multiphase flows and the finite difference method for heat transfer. Simulations are conducted by varying boiling number (Bo) from 0.0023 to 0.0460 at an initial Reynolds number of 100 for four morphologies: single-concave, rectangular-groove, wavy-groove, and multi-concave. For single-concave morphology, the ratio of concave diameter to droplet diameter (Dc/d) is examined with values of 1.0, 2.0, 3.0, and 3.3. In the other morphologies, cross sections are evaluated with two widths: 0.333d and 0.667d, with identical depths. The results show that the thermal performance of the single-concave morphology is mainly affected by Dc/d. The curved geometry gives the single-concave morphology superiority in boiling heat transfer compared to other morphologies studied in the range 0.0023<Bo<0.0389 at Dc/d=2.0. The curved surface controls the bounce of droplets at high Bo, allowing them to deposit smoothly with a large exposed contact area, and achieve an efficient cooling effect. However, for 0.0389≤Bo, superiority in boiling heat transfer is achieved by the multi-concave morphology, where full film boiling does not occur. The thermal performance of other morphologies is primarily influenced by the cross-sectional width. At a width of 0.667d, the wavy-groove morphology provides comparable performance to the multi-concave morphology within 0.0023<Bo<0.0184, while the multi-concave morphology achieves higher boiling heat transfer at 0.0184≤Bo. Conversely, a smaller width of 0.333d significantly reduces heat transfer. This occurs because the rapid surface isolation hinders droplet access to the heated surface base. Furthermore, the rectangular-groove morphology provides the worst thermal performance due to the restrictions against penetration and smooth deposition over the superheated surface. Thermal and hydrodynamic analysis discovers the significance of the single-concave morphology in enhancing the boiling heat transfer in spray cooling systems.
Junction-based deep mesa termination for multi-kilovolt vertical
β
-Ga2O3 power devices
Authors: Wan Jiangbin , Wang Hengyu , Zhang Chi , Wang Ce , Cheng Haoyuan , Ye Jiandong , Zhang Yuhao , Sheng Kuang
Published: January 2025

Deep mesa is an effective edge termination widely deployed in high-voltage power devices. However, its effectiveness requires the minimal distance between mesa and electrode edge and is susceptible to charges in the dielectric passivation, posing challenges in practical implementation. Here, we propose a deep mesa termination encapsulated by p-type materials, which functions as a reduced-surface-field (RESURF) structure and enables a wide design and process window. We demonstrate the RESURF-mesa design in vertical Ga3O3 diodes. In this design, a 5 μm deep mesa, which is intentionally not aligned with the anode edge, is encapsulated by p-type nickel oxide (NiO). This termination has been applied to devices on three Ga2O3 wafers with epitaxial doping concentrations ranging from 1.2 × 1016 to 5 × 1016 cm−3, enabling an average one-dimensional junction field of 4.2–4.4 MV/cm in all wafers. Additionally, the diode with 1.2 × 1016 cm−3 doping achieves a specific on-resistance (RON,sp) of 4.05 mΩ·cm2 and a breakdown voltage of 3214 V, resulting in a power figure of merit of 2.55 GW/cm2, which is among the highest in multi-kilovolt β-Ga2O3 diodes. The above results demonstrate the RESURF-mesa termination as a versatile and effective solution for wide bandgap and ultra-wide bandgap power devices.
Gust response of an airfoil with a flexible trailing edge
Authors: Cao Yu-Tian , Feng Li-Hao
Published: January 2025

Given that the variable-camber continuous trailing-edge flap can enhance the environmental adaptability of wings, this study experimentally investigates the gust response of an airfoil with a flexible trailing edge. The flexible trailing edge comprises 30% of the airfoil chord length and can adaptively undergo chordwise deformation under flow pressure. The unsteady lift, surrounding flow field, and deformation of the flexible trailing edge are synchronously measured. Compared with the rigid airfoil, the time-averaged lift coefficient of the flexible airfoil increases under gust incoming condition, whereas the standard deviation of the lift coefficient decreases. In the case of a low angle of attack, two representative flow structures with distinct frequencies may be obtained, corresponding to the shear layer and shedding vortex. The shear layer above the upper surface of airfoil fluctuates at gust frequencies. The high-frequency vortex shedding in the wake region is significantly affected by the shear layer. The oscillation of the flexible trailing edge is fully coupled with nearby flow fluctuations, which is divided into four stages in one gust cycle. Additionally, compared with the rigid airfoil, the amplitudes of the shear-layer and velocity fluctuations for the flexible airfoil decrease, indicating that the flexible trailing edge can reduce the influence of gusts on the flow field. At a high angle of attack, dynamic stall occurs. A leading-edge vortex develops above the flexible trailing edge. The induced negative pressure causes the flexible trailing edge to deflect significantly upward, thereby weakening the strength of the leading-edge vortex and alleviating the gust load.
From localization to quantum-dot chains in self-formed core–shell InGaN nanowires emitting in the red
Authors: Deng Rongli , Lin Haibin , Hu Qichuan , Wang Dan , Wu Bo , Nötzel Richard
Published: January 2025

Self-formed core–shell InGaN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy on p-Si (111) are studied by temperature-dependent and time-resolved photoluminescence (PL) spectroscopy. Clear localization and associated photocarrier redistribution can be evidenced by the S-shape temperature dependence of the PL peak energy and inflection of the PL linewidth. An unexpected maximum of the integrated PL intensity as a function of temperature is observed. This maximum is identified as proof that the localized states behave as chains of quantum dots with reduced radiative lifetime due to the combination of strong two-dimensional lateral quantum confinement in the NW core with localization. This is underlined by the time-resolved PL measurements exhibiting a fast, sub-ns, single-exponential decay, in addition evidencing negligible quantum-confined Stark effect for efficient light sources emitting in the red.
Instability of non-isothermal viscous liquid jets
Authors: Qiao Ran , Mu Kai , Zhao Chengxi , Si Ting
Published: January 2025

A linear temporal instability analysis of a viscous liquid jet in ambient gas under a thermal field is conducted. The basic temperature profile is derived analytically based on the thermal conduction equation and corresponding boundary conditions. The effects of several control parameters, including the temperature ratio (Tr), Marangoni number (Ma), and Péclet number (Pe), on non-isothermal jet instability are systematically examined through parametric studies. An energy budget method is employed to evaluate the contributions of all physical mechanisms to the kinetic energy. The results reveal that reducing Tr promotes the jet instability. For jets with Tr>1, the maximum growth rate increases with the decrease in Ma or the increase in Pe, indicating that Marangoni stress and thermal conductivity suppress the instability of hot jets. Variations in these control parameters also influence the most dangerous and cutoff wavenumbers. Furthermore, the energy budget analysis reveals a transition in the dominant instability mechanisms between Rayleigh–Plateau and Marangoni instabilities. Specifically, enhancing the Marangoni stress or suppressing the thermal conductivity for hot jets shifts the dominant mechanism from Rayleigh–Plateau instability to Marangoni instability. Phase diagrams in various control parameter spaces are presented to predict transitions in the dominant instability mechanism.
The impact of community water ecological design on promoting health behaviours among the elderly
Authors: Li Hong , Shi Li , Wang Fang-liang
Published: January 2025

Context With the aging population, community water ecological design plays a critical role in promoting the health behaviours of the elderly by enhancing environmental perception, psychological comfort, and community satisfaction. Aims This study investigates the direct and indirect effects of community water ecological design on health behaviours of the elderly, utilising the social–ecological model to explore mediating pathways. Methods A questionnaire survey of 315 elderly individuals (aged 60 and above) in Guangzhou, China, was conducted, covering dimensions such as water ecological design, environmental perception, psychological comfort and health behaviours. Structural equation modelling was used for data analysis. Key results Community water ecological design significantly enhances environmental perception, psychological comfort and community satisfaction of the elderly, which directly and indirectly influence health-behaviour intentions and actual behaviours through multiple mediating mechanisms. Conclusions Community water ecological design is a significant determinant of the health behaviours of the elderly, exerting both direct and indirect influences on well-being through improved environmental perception, psychological comfort and community satisfaction. Implications Optimising water ecological design elements can improve the health outcomes of elderly populations, providing theoretical and practical support for creating elderly-friendly communities.
Phase formation and phase stability for the homogenous and heterogeneous amorphous metals versus the crystalline phase
Authors: Shen Yidi , Samwer Konrad , Johnson William L. , Goddard William A. , An Qi
Published: January 2025

From molecular dynamics (MD) simulations of melt-quenching and thermal aging procedures in pure Ag, Cu, Ag–Cu binary alloys, and Cu–Zr binary alloys, we have identified two distinct amorphous phases for a metastable undercooled liquid: the homogeneous L-phase with low shear rigidity and the heterogenous G-phase with much higher shear rigidity and a heterogeneity length scale Λ. Here, we examine two-phase equilibration studies showing that the G-phase melts to form the L-phase above ~1,000 K, which then transforms to form the crystal (X) phase; however, below the melting point of the G-Phase (~990 K), the X- and G-phases do not transform into each other. We suggest the presence of a G-phase is likely responsible for embrittlement often observed in metallic glasses. We also consider how mechanical milling or irradiation-induced defect accumulation in the crystalline metallic alloy triggers a crystal-to-glass transition. We use the Cu
2
Zr system as a model to investigate random interchange of Zr and Cu atoms at room temperature leading to a transition from a crystalline Laves-phase to an L-glass through formation and growth of amorphous regions and destabilization of the crystal. During relaxation of the nonequilibrium structures by annealing, the configurations either reverted to the crystalline phase or evolve to a heterogeneous G-phase equivalent to the G-phase formed during thermal quenching and aging of the melt. Athermal defect accumulation in the G-phase at low temperature led to a transition back to the L-phase. Our findings show how athermal disordering drives transitions among the X-, L-, and G-phases.
Advancing forecasting capabilities: A contrastive learning model for forecasting tropical cyclone rapid intensification
Authors: Wang Chong , Yang Nan , Li Xiaofeng
Published: January 2025

Tropical cyclones (TCs), particularly those that rapidly intensify (RI), pose a significant threat due to the uncertainty in forecasting them. RI TC periods, which intensify by at least 13 m/s within 24 h, remain challenging to forecast accurately. Existing models achieve a probability of detection (POD) of 82.6% and a false alarm rate (FARate) of 27.2%. To address this, we developed a contrastive-based RI TC forecasting (RITCF-contrastive) model, utilizing satellite infrared imagery alongside atmospheric and oceanic data. The RITCF-contrastive model was tested on 1,149 TC periods in the Northwest Pacific from 2020 to 2021, achieving a POD of 92.3% and a FARate of 8.9%. RITCF-contrastive improves on previous models by addressing sample imbalance and incorporating TC structural features, leading to a 11.7% improvement in POD and a 3 times reduction in FARate compared to existing deep learning methods. The RITCF-contrastive model not only enhances RI TC forecasting but also offers a unique approach to forecasting these dangerous weather events.
Nav1.8, an analgesic target for nonpsychotomimetic phytocannabinoids
Authors: Ghovanloo Mohammad-Reza , Tyagi Sidharth , Zhao Peng , Waxman Stephen G.
Published: January 2025

Pain impacts billions of people worldwide, but treatment options are limited and have a spectrum of adverse effects. The search for safe and nonaddictive pain treatments has led to a focus on key mediators of nociceptor excitability. Voltage-gated sodium (Nav) channels in the peripheral nervous system—Nav1.7, Nav1.8, and Nav1.9—play crucial roles in pain signaling. Among these, Nav1.8 has shown promise due to its rapid recovery from inactivation and role in repetitive firing, with recent clinical studies providing proof-of-principal that block of Nav1.8 can reduce pain in humans. We report here that three nonpsychotomimetic cannabinoids—cannabidiol (CBD), cannabigerol (CBG), and cannabinol (CBN)—effectively inhibit Nav1.8, suggesting their potential as analgesic compounds. In particular, CBG shows significant promise due to its ability to effectively inhibit excitability of peripheral sensory neurons. These findings highlight the therapeutic potential of cannabinoids, particularly CBG, as agents that may attenuate pain via block of Nav1.8, warranting further in vivo studies.
Global urban greening and its implication for urban heat mitigation
Authors: Li Guangdong , Cao Yue , Fang Chuanglin , Sun Siao , Qi Wei , Wang Zhenbo , He Sanwei , Yang Zhiqi
Published: January 2025

Urban vegetation provides essential ecosystem services and benefits to support biodiversity and human well-being in urban areas. However, the dynamic trends, driving factors, and their implications to urban heat mitigation at the global scale remain largely unclear. Here, we used a high-resolution enhanced vegetation index (EVI) dataset to examine the vegetation dynamics in 11,235 urban areas worldwide, identify the driving factors behind its changes, and estimate the potential urban heat mitigation benefits of these changes. We found that 40.75% urban areas (1.51 Mha) evidenced a greening trend (showing increasing EVI), in contrast to 49.60% urban areas showing browning (decreasing EVI). Notably, urban centers in both developed and developing countries contribute to this greening trend. We, nevertheless, found significant spatial disparities in this greening trend, with cities in the Global North showing higher greening ratios than those in the Global South. The driving factors of urban vegetation change trend lead to significant differentiation in and around urban areas. The rapid increase in urbanization intensity and the negative effects of nitrogen deposition are the dominant factors leading to vegetation browning in urban peripheries. However, nitrogen deposition and urbanization intensity have shown positive effects on vegetation greening within urban centers. Crucially, compared to areas with vegetation browning or no significant change, vegetation greening areas have a more significant cooling effect, potentially mitigating the urban heat island effect, especially during summer daytime. Our findings highlight the importance of enhancing urban vegetation greening to promote equitable urban development and ensure effective climate change mitigation.
Fool them before they fool you
Authors: Valchev Hristo , Hample Dale , Hample Jessica M.
Published: January 2025

Bulgarian people have a long history and an enduring national identity, significantly defined by their continuing
allegiance to Eastern Orthodox Christianity. Here we investigate how Bulgarians understand the prospect of interpersonal argument.
Our instruments assess Bulgarians’ arguing motivations, their understandings of the practice of arguing face to face, their
emotional reactions to interpersonal disagreement, their tolerance of status inequalities in society, and their willingness to
argue at work. We have data from 287 Bulgarians (39% male, 61% female), having an average age of 37 years. We uncovered very few
differences between men and women. We found older Bulgarians less eager to argue in typical social situations, though they were
not hesitant to argue with their superiors at work. They were more polite and cooperative when they did argue. Bulgarians who were
most comfortable with status inequities in society were reluctant to argue with their superiors, were noticeably willing to
produce ad hominem arguments, and generally had an aggressive impolite profile of arguing orientations. Poland
and Ukraine are natural comparisons because of their shared political histories in the last several generations. We also do a
comparison with the U.S., as a general standard of comparison because our theories and measures originated in the U.S.
Superquestions and some ways to answer them
Authors: D’Agostino Giulia , Schad Ella , Maguire Eimear , Lucchini Costanza , Rocci Andrea , Reed Chris
Published: January 2025

Earnings Conference Calls, in which corporate management are quizzed by investment analysts, are a particularly
rich source of a phenomenon of question-asking that, though less prevalent, also occurs in many other genres of discourse. When a
participant in a dialogue is allowed to ask more than one question consecutively — particularly in order to extend or refine or
recast — we see that respondents often react by answering either one or more of the individual questions, or by answering a
question that was never actually asked, but which is related to the explicit questions and to other content introduced in the
turn. We call this overarching implicit question a superquestion, and explore how they can be formed, how they
can be answered, how they trigger argumentation, and, indeed, how they can be dodged.