bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphology and selectivity of hydrated alkali metal ions as depth of discharge in the 1T-MoS2 electrode with aqueous electrolytes
Authors: Liao Shenrui , Zhao Wenhui , Gu Xiao
Published: March 2024

Hydration and concentration of alkali metal ions play essential role in the intercalation into 2D 1T-MoS2 and the ion selectivity also depends on both discharge depth and hydration degree.
Defect-less formamidinium Sn–Pb perovskite grown on a fluorinated substrate with top-down crystallization control for efficient and stable photovoltaics
Authors: Zhou Yuan , Guo Tonghui , Jin Junjun , Zhu Zhenkun , Li Yanyan , Wang Shuxin , Zhou Sisi , Lin Qianqian , Li Jinhua , Ke Weijun , Fang Guojia , Zhang Xianggong , Tai Qidong
Published: March 2024

A highly efficient and stable ideal-bandgap perovskite solar cell based on a defect-less formamidinium (FA) Sn–Pb perovskite light-absorbing layer is grown on a fluorinated substrate via top-down crystallization.
Three-component approach to modular synthesis of tetra-substituted furans and pyrroles
Authors: Zhang Pei , Ti Wenqing , Gao Tianfeng , Zhu Jie , Lin Aijun , Gao Shang , Li Xuanyi , Yao Hequan
Published: March 2024

A three-component one-pot reaction of TMSCF2Br, p-QMs and 1,3-dicarbonyl compounds and derivatives was developed. A series of densely functionalized tetra-substituted furans and pyrroles were constructed with excellent chemoselectivities.
Covalent organic framework isomers with divergent photocatalytic properties
Authors: Ren Xitong , Wen Mengyao , Hou Xiaobin , Sun Jiajie , Bai Feng , Li Yusen
Published: March 2024

Minute structural variations in Py-BT-COF isomers can generate significant differences in redox and photophysical properties, resulting in divergent photocatalytic performances in H2 reduction and rhodamine B degradation.
Synthesizing Pd-based high entropy alloy nanoclusters for enhanced oxygen reduction
Authors: Zhang Fan , Sun Shiwei , Ge Xiaohang , Guan Qinhe , Ling Miao , Yuan Weiyong , Zhang Lian Ying
Published: March 2024

We report the synthesis of uniform Pd-based HEA clusters on an XC-72 carbon support using a rapid Joule heating method. The quinary PdMnFeCuNi clusters exhibit outstanding stability and 4.95 times higher mass activity than the Com Pt/C for the ORR.
Fabrication of BiVO4 submicron rods photoanodes through phase transition assisted by Mo doping
Authors: Zhao Shuang , Zhang Haipeng , Wang Zhaoqi , Xiao Deifei , Xu Xianbin , Wang Peng , Zheng Zhaoke , Liu Yuanyuan , Dai Ying , Cheng Hefeng , Wang Zeyan , Huang Baibiao
Published: March 2024

Herein, Mo doping has been found to effectively lower the phase transition temperature from tetragonal zircon BiVO4 to monoclinic scheelite BiVO4. Our research introduces a novel method for the production of submicron rods BiVO4 photoanodes.
Homochiral vs. heterochiral preference in chiral self-recognition of cyclic diols
Authors: Dupont Jennifer , Hartwig Beppo , Le Barbu-Debus Katia , Lepere Valeria , Guillot Regis , Suhm Martin A. , Zehnacker Anne
Published: March 2024

Substitution of the transiently chiral cis-1,2-cyclohexanediol (cis-CD) by a phenyl results in (S,S)-(+)-1-phenylcyclohexane-cis-1,2-diol (cis-PCD) and modifies the hydrogen bond pattern in its dimer. The heterochiral preference observed in cis-CD changes for homochiral in cis-PCD.
Recent advances in Chan–Lam coupling reaction
Authors: Devi P. S. , Saranya Salim , Anilkumar Gopinathan
Published: March 2024

Chan–Lam coupling has evolved as a shining star among C–heteroatom coupling reactions because of its greener open flask chemistry and tremendous possibilities in terms of substrate bank, catalyst varieties, unlocking nature friendly conditions, etc.
Dispersing agglomerated Zn4In2S7 on g-C3N4 nanosheets to form a 2D/2D S-scheme heterojunction for highly selective photocatalytic cleavage of lignin models
Authors: Lu Yitong , Fan Yu , Xu Shuai , Li Yuliang
Published: March 2024

Successfully dispersed the Zn4In2S7 clusters, synthesizing 2D/2D S-scheme heterojunction photocatalyst, showing excellent ability to selectively cleave Cβ–O bonds in lignin.
Pathway and enzyme engineering for the bioconversion of lignin derivatives into homoeriodictyol in Saccharomyces cerevisiae
Authors: Zhu Si-Yu , Liu Shi-Chang , Zhang Chuan-Xi , Xin Xin , Liu Zhi-Hua , Zhang Lu-Jia , Li Bing-Zhi , Yuan Ying-Jin
Published: March 2024

The innovative bioconversion route of lignin derivatives to homoeriodictyol meets the atom-economic concept, and paves a green, sustainable way for both the valorization of lignin and the production of valuable flavonoids.
Chemical valorisation of biomass derived furanics and carboxylic acids over niobium-based catalysts
Authors: Antunes Margarida M. , Skrodczky Kai , Cabanelas Pedro S. , Pinna Nicola , Russo Patrícia A. , Valente Anabela A.
Published: March 2024

Reaction and substrate scopes may be considerably broadened in the context of the chemical valorisation of biomass, using stable solid acid catalysts consisting of nanostructured silica–niobia which outperformed pure niobia and other catalysts.
Bioderived silicon nano-quills: synthesis, structure and performance in lithium-ion battery anodes
Authors: Chen Nancy , Sabet Morteza , Sapkota Nawraj , Parekh Mihir , Chiluwal Shailendra , Koehler Kelliann , Clemons Craig M. , Ding Yi , Rao Apparao M. , Pilla Srikanth
Published: March 2024

Water-dispersible silicon nano-quills (SiNQs) with unique porous morphology and composition promote the advancement of high-Si-content anodes with fast charging/discharging capabilities.
Distance-based paper analytical device for multiplexed quantification of cytokine biomarkers using carbon dots integrated with molecularly imprinted polymer
Authors: Khachornsakkul Kawin , Del-Rio-Ruiz Ruben , Chheang Lita , Zeng Wenxin , Sonkusale Sameer
Published: March 2024

A carbon dots and dopamine-imprinted polymer was immobilized onto a distance-based paper channel for simultaneous detection of three cytokine biomarkers without requiring expensive reagents and instruments.
Photodeposited nickel-loaded ZnCdS nanoparticles for hydrogen production from photocatalytic water splitting
Authors: Huang Xiaorun , Guo Changyan , Niu Yanan , Ma Yanqiu , Wang Jide
Published: March 2024

The application of non-noble metal catalysts to photocatalytic hydrogen production from water holds a high practical application value.
2-Azabicyclo[3.2.1]octane scaffold: synthesis and applications
Authors: Crespo Monteiro Mariana , Vale João Rafael , Siopa Filipa
Published: March 2024

This review focuses on the preparation and applications in total synthesis of 2-azabicyclo[3.2.1]octane structures, a class of natural and synthetic compounds with a range of biological activities.
Phase behavior of colloidal nanoparticles and their enhancement effect on the rheological properties of polymer solutions and gels
Authors: Yang Liu , Ge Jiiang , Wu Hao , Guo Hongbin , Shan Jingling , Zhang Guicai
Published: March 2024

The SiO2 nanoparticles exhibit stronger aggregate tendency in the negatively charged polymer solutions, therefore enhancing the viscosity of polymer solutions and the mechanical properties of their gels.
Structural and morphological investigation of (R)-α-phenylethylammonium-oxalate in bulk vs. nanowires on a modified substrate surface
Authors: Burazer Sanja , Košutová Tereza , Horák Lukáš , Dopita Milan , Šantić Ana , Fučíková Anna
Published: March 2024

Different forms of a chiral organic insulator, (R)-α-phenylethylammonium-oxalate (RAPEAO), was prepared: single crystal, powder and spin-coated layers on silicon substrate surfaces modified by plasma treatment or a polymer layer.
Form II to form I transition in solution-crystallized isotactic polybutene-1
Authors: Fu Peng , Huo Jiaxin , Li Jingqing , De Rosa Claudio , Jiang Shichun
Published: March 2024

Different polymer chains in a solution or melt have different conformations with corresponding entropy at each moment, which would be confined after crystallization.
A Comparison of Autistic and Non-Autistic College Students' Perceived Challenges and Engagement in Self-Advocacy
Authors: Santhanam Siva priya , Wilson Kaitlyn
Published: March 2024

Purpose:

Autistic students experience lower college graduation rates than their peers, affecting future opportunities. Self-advocacy is crucial for successful adaptation in postsecondary settings and is documented as a challenge for autistic students. The purpose of the study was to examine autistic college students' engagement in self-advocacy and specific college-related challenges as compared to their neurodivergent and neurotypical peers.

Method:

This study used a cross-sectional survey design to compare perceptions related to self-advocacy and college-related challenges across three groups of students: autistic students, students with a disability other than autism, and nondisabled students. Descriptive and inferential statistics were used to compare survey responses across groups.

Results:

Differences in the groups' perceptions of their engagement in overall self-advocacy and specific self-advocacy strategies were evident. Autistic students rated themselves significantly lower on self-advocacy than did students with other disabilities. When compared to their nondisabled peers, the autistic students and those with other disabilities were less likely to report comfort interacting in the classroom, including less interest in group work, and more difficulty interacting with unfamiliar peers. In addition, the autistic students were more likely to report difficulty recognizing the need for academic assistance when compared to both peer groups. Autistic students also reported greater social challenges in the college setting than their nondisabled peers, and both neurodivergent groups of students reported significantly more challenges, overall, navigating the college setting than did their nondisabled peers.

Conclusions:

Findings highlight the need for systematic, individualized self-advocacy supports for autistic and other neurodivergent college students. In addition, findings show the need to educate peers and professors about autism and self-advocacy to foster a welcoming college environment. Finally, findings suggest the need for increased social support and opportunities for social integration within postsecondary settings. Speech-language pathologists play a critical role in implementing these next steps.
A Simple Estimation Scheme for Leak Detection in Pipelines
Authors: Nguyen Thang , Nguyen Binh Thanh , Pham Duc Dai
Published: March 2024

This paper presents a simple high-gain observer to detect water leak in a pipeline system. The estimation scheme was developed based on the nonlinear model of the pipeline system. A simulation was conducted to illustrate the potential of the proposed method.
Predicting future salinity variability in the Ca Mau Peninsula due to Climate Change
Authors: Anh Duong Tran , Gagnon Alexandre S. , Tanim Ahad Hasan , Wright David , Thanh Phong Nguyen
Published: March 2024

The Ca Mau Peninsula (CMP) in Vietnam’s Lower Mekong Delta faces pressing challenges, including sea-level rise (SLR), land subsidence, flooding, and saltwater intrusion. Recent years have witnessed an earlier and more severe dry season, leading to heightened saltwater intrusion. As many CMP provinces rely on the Mekong River for their water supply, they are highly susceptible to prolonged drought and salinization. This study employs the MIKE 11 hydraulic model to project saltwater intrusion scenarios in the CMP up to 2050, based on Vietnam’s 2016 Ministry of Natural Resources and Environment (MONRE) SLR projections, considering water regulation from the Cai Lon-Cai Be sluice system. The modelled discharge, water level and salinity were calibrated and validated successfully based on di_erent statistical measures. The projections indicate that saltwater intrusion during the dry season could start 1 to 1.5 months earlier by 2050, with salinity levels exceeding 30 g/l in February. The findings underscore the importance of developing adaptation strategies to address the challenges of climate change and saltwater intrusion, notably in the region’s significant agricultural sector.
Monorail bridge inspection using digitally-twinned UAVs
Authors: Nguyen Lanh V. , Le Trung H. , Nguyen Thao D. , Kwok Ngai M. , Ha Quang P.
Published: March 2024

This paper introduces a comprehensive approach to monorail bridge inspection utilizing unmanned aerial vehicles (UAVs) and digital twin technology. The autonomous UAV-based inspection design encompasses UAV dynamics, tracking control, path planning, and task execution. A dedicated digital twin platform is developed to facilitate rigorous testing and verification of UAV control, mitigating the necessity for extensive physical testing. Methodology validation is achieved through a combination of simulations and real-world experiments, affirming its efficacy in authentic scenarios and demonstrating the potential for advancing infrastructure inspection practices.
Structural dynamics at surfaces by ultrafast reflection high-energy electron diffraction
Authors: Horn-von Hoegen Michael
Published: March 2024

Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond timescale. In order to study such ultrafast processes, we have combined modern surface science techniques with fs-laser pulses in a pump–probe scheme. Grazing incidence of the electrons ensures surface sensitivity in ultrafast reflection high-energy electron diffraction (URHEED). Utilizing the Debye–Waller effect, we studied the nanoscale heat transport from an ultrathin film through a hetero-interface or the damping of vibrational excitations in monolayer adsorbate systems on the lower ps-timescale. By means of spot profile analysis, the different cooling rates of epitaxial Ge nanostructures of different size and strain state were determined. The excitation and relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated using the In-induced (8 × 2) reconstruction on Si(111). This Peierls-distorted surface charge density wave system exhibits a discontinuous phase transition of first order at 130 K from a (8 × 2) insulating ground state to (4 × 1) metallic excited state. Upon excitation by a fs-laser pulse, this structural phase transition is non-thermally driven in only 700 fs into the excited state. A small barrier of 40 meV hinders the immediate recovery of the ground state, and the system is found in a metastable supercooled state for up to few nanoseconds.
Cavitation in a binary Lennard–Jones mixture: van der Waals gradient theory and molecular dynamics simulation
Authors: Baidakov V. G. , Bryukhanov V. M.
Published: March 2024

The size dependence of the surface tension of critical bubbles in a superheated (stretched) Lennard–Jones solution with complete solubility of the components is considered. Two approaches are used to determine this dependence. The first one is based on the van der Waals gradient theory, and the second one is based on molecular dynamic simulation results of nucleation in a solution. It is established that, unlike in a one-component liquid, where the surface tension of the equilibrium bubble is less than that for the flat interface, in solution, it can exceed the flat limit. The ranges of temperatures, pressures, and mixture compositions, where this effect occurs, are determined. The asymptotic behavior of the surface tension of vapor phase nuclei within the limits of zero and infinitely large curvature of the dividing surface is analyzed.
Influence of cavitation on vortical structures and energy loss in a waterjet pump
Authors: Gong Bo , Feng Chao , Li Ning , Ouyang Xiaoping , Yin Junlian , Wang Dezhong
Published: March 2024

Cavitation-induced vortex and energy loss are critical topics in the field of hydraulic machinery. Through a combination of experimental and numerical analysis, this paper investigates how blade loading affects vortical structures and energy loss during cavitation in a waterjet pump. The flow rate and cavitation conditions changed blade tip pressure loading, which significantly affected the trajectories of the primary tip leakage vortex cavitation and secondary tip leakage vortex cavitation. A considerable pressure gradient at the attached cavity closure region leads to a wall reentrant jet and a side-entrant jet, resulting in an attached vortex under the cavitation developing stage and severe stage. The development of the attached vortex leads to the shedding of attached cavities. Furthermore, the blade tip pressure difference loading significantly alters the distribution of tip leakage vortex and gives rise to a perpendicular leakage vortex (PLV). The PLV entrains the shedding cavities and forms a perpendicular cavitation vortex. These complex vortical structures induced by cavitation inevitably enhance enstrophy and lead to entropy production in the pump. The entropy production terms of viscous dissipation, turbulent dissipation, and the wall effect react differently to the development of cavitation. As the cavitation stages developed and became more severe, wall entropy production (S3) decreased. While turbulent dissipative entropy production S2 due to mixing losses occurring in the tip region increased sharply, which dominates the total entropy production S and results in an increase in S.
Experimental investigation of flow patterns and rheological characteristics of compressed air foam in horizontal tube
Authors: Li Hongsheng , Liu Songyong , Jin Cuijun , Xu Panpan , Wang Juan , Xie Qizhi
Published: March 2024

The use of compressed air foam (CAF) for fire suppression has undergone rapid development in recent years. It has been successfully applied in fire incidents in the petroleum and chemical industries. The increasing need to fighting fires at high elevations necessitates an understanding of the rheological characteristics, pressure gradient changes, flow characteristics, and regularities of CAF within long firehoses. Therefore, this paper focuses on an investigation of the flow characteristics of CAF at foaming agent concentrations ranging from 0.1% to 1.2% and gas–liquid ratios ranging from 5 to 25. Specifically, it explores foam characteristics, pressure loss, and the relationship between flow rate and foaming agent concentration. The findings reveal that CAF exhibits four flow patterns: wave flow, elastic flow, ring flow, and dispersion flow. For most CAF firefighting applications, a foaming agent concentration of 0.3%–0.5% and a gas–liquid ratio of approximately 10 are suitable. However, for fire isolation purposes, a foaming agent concentration of 0.7%–1.0% and a gas–liquid ratio of over 15 should be employed. By utilizing a power-law rheological model and an experimental regression method, a prediction model is obtained for the flow characteristics and pressure loss of CAF in pipelines. The predictions of the model exhibit an error of less than 10% when compared with experimental results, validating the model. The results of this study provide a theoretical basis and technical support for understanding liquid supply resistance loss, which is crucial for maximizing firefighting effectiveness.
Experimental study on contact time of a water droplet impact under controlled surface temperature
Authors: Gao Shu-Rong , Jia Qi-Hui , Shi Shi-Hua , Liu Zhe , Wei Bo-Jian , Wang Yi-Feng , Zheng Shao-Fei , Yang Yan-Ru , Wang Xiao-Dong
Published: March 2024

Bouncing droplets on superhydrophobic surfaces is one of the potential methods used for anti-icing. The surface supercooling is a significant parameter influencing the bouncing dynamic. A droplet impacting cold superhydrophobic surfaces is investigated via experimental methods. The influence of the surface supercooling and the Weber number on the impact dynamic is elucidated. Intriguingly, the surface supercooling shows no influence on the spreading time, and the initial retraction time as the heat exchange can be ignored in these processes, while it shows a strong influence on the late retraction time as it can lead to the wetting transformation. To further quantitatively describe the influence of surface supercooling, the relationships of the retraction rate in the late retraction are developed, considering the changes in the receding contact angle caused by the supercooling degree. Finally, the relationship of the contact time is established over a range of Weber numbers (We = 49.37–70.53), surface supercooling (ΔT = 15–24 °C), and droplet sizes (D0 = 2.2–3.2 mm). This work is the first to establish the relationship of the droplet contact time on cold superhydrophobic surfaces, which can provide a quantitative method to calculate the contact time for anti-icing.
Transforming the transportation sector: Mitigating greenhouse gas emissions through electric vehicles (EVs) and exploring sustainable pathways
Authors: Kumar Rohan , Kanwal Ammara , Asim Muhammad , Pervez Mohsin , Mujtaba M. A. , Fouad Yasser , Kalam M. A.
Published: March 2024

Transportation-related emissions in Pakistan have been rapidly increasing in recent years. This study aims to determine how important it is to electrify road transportation in Pakistan to reduce greenhouse gas (GHG) emissions from the transportation sector. Motivated by the need to tackle the growing environmental issues related to conventional fuel-powered automobiles, this research explores the application of electrification techniques in the context of Pakistan’s transportation system. During the 2019 fiscal year, the transportation industry in Pakistan consumed 23 × 106 tonnes of energy from the burning of fossil fuels and produced 52.9 × 106 metric tons of CO2, which made up 31% of the country’s total carbon emissions. In this research, different scenarios, such as business as usual, low carbon, strengthen low carbon, and Pakistan National Electric Vehicle Policy 2040, are evaluated for the transportation sector of the country. Using the LEAP model, this study projects the effects of electrification on Pakistan road transportation over 30 years. When estimating how electrification will affect road transportation in Pakistan over the next 30 years, several factors were taken into account, including policy frameworks, changing consumer behavior, technology advancements, and infrastructure improvements. The analysis covered the emission levels, adoption hurdles, and possible advantages of transitioning to electric vehicles (EVs). The outcomes illustrate that adopting EVs can produce substantial drops in fuel consumption and environmental emissions, providing a sustainable solution to mitigate global warming. This work is directly associated with various Sustainable Development Goals, including SDG3 (good health and well-being), SDG7 (affordable and clean energy), and SDG13 (climate action). The results of this study highlight the considerable potential for GHG reduction associated with the widespread adoption of EVs, offering crucial insights to stakeholders and policymakers.
Analysis of axial force and pressure pulsation of centrifugal pump as turbine impeller based on dynamic mode decomposition
Authors: Li Peixuan , Dong Wei , Jiang Haoqing , Zhang Haichen
Published: March 2024

To investigate the spatiotemporal evolution mechanism of the axial force on a centrifugal pump acting as a turbine, this study focuses on a single-stage single-suction centrifugal pump and applies dynamic mode decomposition (DMD) to decompose the flow field of the turbine impeller's axial force. The axial force of the impeller under three flow conditions, namely, 1.0Qd, 1.3Qd, and 1.6Qd, is extracted and analyzed. Results show that the DMD method can accurately extract the spatiotemporal coherent structural characteristics of the main modes of axial force, with the first five modes accounting for more than 99.97% of the total mode energy. Under the 1.3Qd condition, the flow field is stable, and the axial force remains constant over time with a very small degree of pressure pulsation. However, under the 1.6Qd condition, the flow field inside the pump becomes complex and unstable, leading to larger changes in axial force compared to the 1.0Qd condition, with an increase in 2.13 times. The amplitude of the pressure pulsation gradually decreases from the impeller inlet to the outlet under both 1.0Qd and 1.6Qd conditions, with vibration caused by the axial force mainly occurring at the impeller inlet. These findings provide a reference basis for improving the stability of centrifugal pumps acting as turbines.
Experimental investigation of characteristics of turbulence induced by multiple oscillating grids
Authors: Li Qijun , Cheng Nian-Sheng
Published: March 2024

Experiments were conducted to systematically investigate the nearly homogeneous turbulence generated by multiple oscillating grids. Altogether 54 runs were completed by employing five different grids. For each run, four to nine layers of grids were installed, which were operated with different frequencies, strokes and grid spacings. The particle image velocimetry was used to obtain flow velocity characteristics. Instantaneous flow measurements reveal that the flow structure varies depending on the grid configuration. For regular grids, turbulent wakes of nearly uniform size were generally observed. In comparison, for double-scale grids, the size of wakes varied with the bar width. In the near-grid region, the horizontal distributions of Reynolds stresses are strongly influenced by the grid geometry, showing obvious inhomogeneity especially for wide bars. The inhomogeneity reduces as the distance from the grid increases. At the midplane between two neighboring grids, the flow characteristics appear similar for all grid configurations. The size of the region where the turbulence appears nearly homogeneous is affected by the grid spacing and stroke. Generally, the double-scale grid can produce a greater homogeneous region than the regular grid. This study shows that the decay law of turbulence intensity developed for a single oscillating grid can be successfully extended to multiple oscillating grids. In addition, a theoretical interpretation of the decay law is presented by considering the variation in the velocity and size of wakes when evolving away from the grid.
Deformation characteristics of a ring-stiffened cylindrical shell induced by shock waves and coalesced bubbles in double-charge underwater explosions
Authors: Zhang Yifan , Liu Liangtao , Wang Jinxiang , Ma Teng , Liu Kun , Chen Xiwen
Published: March 2024

This study investigates the deformation characteristics of a ring-stiffened cylindrical shell induced by shock waves and coalesced bubbles in double-charge underwater explosions. A numerical model for coupling underwater multi-point explosion loads with the cylindrical shell is established by the Arbitrary Lagrange Euler method, and underwater explosion experiments with double charges are also conducted. The numerical model's effectiveness is validated by comparing shock wave superposition characteristics, bubble coalescence processes, and bubble pulsation periods with the experimental results. Based on the numerical model, the influences of detonation intervals and layout angles of charge on shock wave superposition effects, temporal and spatial distribution characteristics of shock waves, and the evolution process of coalesced bubbles in underwater explosions with double charges are explored. Additionally, the deformation characteristics of cylindrical shells induced by shock waves and coalesced bubbles for double charges with different detonation intervals and layout angles of charge are analyzed. The results indicate that double charges can induce more substantial deformation on the cylindrical shell at a specific detonation interval than a single charge with equal total mass. During the shock wave phase, the cylindrical shell's deformation decreases nonlinearly with an increased layout angle. Conversely, during the bubble load phase, the deformation of the cylindrical shell shows an approximately linear decrease with an increase in layout angle. A critical angle exists, below which the impact of double charges on the cylindrical shell is more substantial when detonated with an interval than simultaneous detonation.
Numerical investigation of no-load startup in a high-head Francis turbine: Insights into flow instabilities and energy dissipation
Authors: Sun Longgang , Liu Lei , Xu Zhuofei , Guo Pengcheng
Published: March 2024

The presented paper numerically investigates the internal flow behaviors and energy dissipation during the no-load startup process toward a Francis turbine. Passive runner rotation is implemented through the angular momentum balance equation accompanied by dynamic mesh technology and user defined function. Three phases of rotational speed are identified: stationary, rapid increase, and slow increase. Head exhibits a monotonic decrease, rapid rise and fall, and eventual fluctuation. Flow rate shows quasi-linear increase. The pressure fluctuations in the vaneless region are primarily dominated by the frequencies induced by Rotor-Stator Interaction and a broad frequency range below 50 Hz, and below 30 Hz in the draft tube. Runner inlet experiences positive to negative incidence angles, causing intense flow separation and unstable structures. Draft tube exhibits large-scale recirculation and evolving vortex structures. Energy loss analysis based on the entropy production method highlights the runner and draft tube as primary contributors. The energy loss within the runner exhibits an initial increase, subsequent decrease, and then a rise again during the stationary and rapid speed increase phases. While the draft tube shows a rapid increase during the phase of rapid speed increase. Turbulent fluctuations significantly contribute to entropy production loss, with trends matching total entropy production. Maximum energy loss locations correspond to runner inlet and draft tube wall, emphasizing the importance of unstable flow and vortex generation. This study establishes foundational insights into unstable hydrodynamics and energy dissipation modes during hydraulic turbine no-load startup, paving the way for further research.
Mixed convection of a viscoplastic fluid with a variable yield stress in a lid-driven cavity
Authors: Rezaee Danial , Samari Alireza , Azad Amirreza
Published: March 2024

This study is a numerical investigation on heat and momentum transfer in viscoplastic fluids that exhibit a variable yield stress. Viscoplastic fluids are recognized for transitioning from solid to liquid under flow-induced shear-rate. However, these materials exhibit intricate rheological behaviors beyond this fundamental characteristic, often linked to thixotropy. Thixotropy delineates reversible, time-dependent alterations in a fluid's viscosity at a specific shear-rate. The temporal changes in viscosity stem from variations in the fluid's microstructure, responsive to the induced shear-rate. When subjected to shear, the fluid's microstructure breaks down into smaller units, countered by Brownian motion, resulting in a rearrangement of the microstructure due to attractive forces between microconstituents. These microstructural variations are thus reversible. Notably, these changes affect not only viscosity but also the yield stress of the fluid, categorizing it as a non-ideal yield-stress fluid with yield-stress variations linked to microstructure, termed isotropic hardening. This study aims to explore how variations in yield-stress fluid microstructure impact heat and momentum transfer. As a starting point, this study considers the lid-driven cavity flow with differentially heated walls in the presence of an external magnetic field. Addressing the yield-stress fluid microstructure variations involves utilizing the Houska–Papanastasiou model, a regularized model capturing thixotropy and isotropic hardening. The resulting governing equations are made dimensionless and numerically solved through the finite-element method. The findings indicate that a more pronounced breakdown of the fluid's microstructure correlates with a higher Nusselt number at the hot wall. Additionally, variations in fluid microstructure influence both the size and location of unyielded zones.
Effect of surface roughness on large-scale downburst-like impinging jets
Authors: Canepa Federico , Burlando Massimiliano , Romanic Djordje , Hangan Horia
Published: March 2024

Downbursts are cold descending winds that develop from thunderstorm clouds and, after impingement on the ground, produce an intense low-level horizontal front characterized by an axisymmetric toroidal vortex structure. Surface roughness is a key factor in the characterization of mean and turbulent wind speed features of synoptic-scale stationary atmospheric boundary layer winds. The goal of the present research is to physically assess whether the same can apply to the surface layer produced during thunderstorms, which are non-stationary, highly time-transient, and spatially limited phenomena. Downburst-like flows were produced through the impinging jet technique at the WindEEE Dome, at Western University in Canada. Three different surfaces were tested, and an equivalent full-scale roughness length (z0,eq) was determined. Experimental records are made publicly available. The large geometric and kinematic scales produced high Reynolds numbers, which enabled us to classify the flow as “fully turbulent” and therefore representative of full-scale downbursts. Results indicate a weak dependency on the Reynolds number, which suggests no relevant flaws in extending the results to the natural environment. The overall wind speed maxima weakly depend on z0, whereas a sharp velocity decrease is observed beyond the radial position of the maxima with increasing z0. Surface roughness enhances the boundary layer separation and consequently elevates the height of maximum wind speed above the surface. Vertical profiles of the horizontal velocity return a quite clear nose shape. Turbulence intensity shows a C-like shape with maxima in the near proximity of the ground that increase with z0.
Weaker land–atmosphere coupling in global storm-resolving simulation
Authors: Lee Junhong , Hohenegger Cathy
Published: March 2024

The debate on the sign of the soil moisture–precipitation feedback remains open. On the one hand, studies using global coarse-resolution climate models have found strong positive feedback. However, such models cannot represent convection explicitly. On the other hand, studies using km-scale regional climate models and explicit convection have reported negative feedback. Yet, the large-scale circulation is prescribed in such models. This study revisits the soil moisture–precipitation feedback using global, coupled simulations conducted for 1 y with explicit convection and compares the results to coarse-resolution simulations with parameterized convection. We find significant differences in a majority of points with feedback that is weaker and dominantly negative with explicit convection. The model with explicit convection is more often in a wet regime and prefers the triggering of convection over dry soil in the presence of soil moisture heterogeneity, in contrast to the coarse-resolution model. Further analysis indicates that the feedback not only between soil moisture and evapotranspiration but also between evapotranspiration and precipitation is weaker, in better agreement with observations. Our findings suggest that coarse-resolution models may not be well suited to study aspects of climate change over land such as changes in droughts and heatwaves.
Unveiling of Terahertz Emission from Ultrafast Demagnetization and the Anomalous Hall Effect in a Single Ferromagnetic Film
Authors: Lan 蓝 Zhiqiang 志强 , Li 李 Zhangshun 章顺 , Xu 徐 Haoran 浩然 , Liu 刘 Fan 凡 , Jin 金 Zuanming 钻明 , Peng 彭 Yan 滟 , Zhu 朱 Yiming 亦鸣
Published: March 2024

Using THz emission spectroscopy, we investigate the elementary spin dynamics in ferromagnetic single-layer Fe on a sub-picosecond timescale. We demonstrate that THz radiation changes its polarity with reversal of the magnetization applied by the external magnetic field. In addition, it is found that the sign of THz polarity excited from different sides is defined by the thickness of the Fe layer and Fe/dielectric interface. Based on the thickness and symmetry dependences of THz emission, we experimentally distinguish between the two major contributions: ultrafast demagnetization and the anomalous Hall effect. Our experimental results not only enrich understanding of THz electromagnetic generation induced by femtosecond laser pulses but also provide a practical way to access laser-induced ultrafast spin dynamics in magnetic structures.
Investigation of temperature and H2 on GePb/Ge multiple quantum well growth
Authors: Liu Xiangquan , Zheng Jun , Huang Qinxing , Cui Jinlai , Zhu Yupeng , Yang Yazhou , Liu Zhi , Zuo Yuhua , Cheng Buwen
Published: March 2024

To reveal the growth behavior of GePb/Ge multiple quantum well (MQW) samples, both the influence of growth temperature and H2/Ar atmosphere are investigated by sputtering epitaxy. As the growth temperature increases from 250 °C to 400 °C, Pb atoms become more active and migrate easily to the surface, forming Pb clusters. As a result, the Pb composition in the GePb/Ge MQW is decreased from 3.5% to 1.8%. When H2 is introduced into the chamber, it is found that the MQW disappears and GePb film with uniform Pb distribution is formed. This is possibly because that the introduction of H2 can retain Pb atoms and the GePb is still grown even if the Pb flux is off. The results show that low temperature and H2 atmosphere are effective methods to further break the low solid solubility limit of Pb in Ge.
Application of Poisson’s ratio structures and decoupling algorithm for 3D force sensing
Authors: Liu Wangyu , Liu Zheng , Guo Zhengqiang , Chen Zhaoqi , Xie Weigui
Published: March 2024

Flexible tactile electronic devices are extensively used in the fields of robotics, medical detection, and human-computer interaction. Monitoring contact parameters, including force magnitude, direction, and contact location, is particularly vital for skin-like tactile sensing devices. Herein, a 3D force sensor is designed based on porous structure with deliberately designed Poisson’s ratios. A genetic algorithm (GA) optimized back propagation neuronal network (BPNN) model is proposed to support the 3D force decoupling, which can greatly improve the decoupling accuracy. The introduction of the GA-BPNN significantly enhances decoupling accuracy compared to the initial neural network. Micro-porous structures with varied Poisson’s ratios are embedded into the sensing unit to achieve better sensibility. Significantly, this study underscores that the decoupling accuracy of the force components along the Z-axis can be further improved by substituting the solid unit with a designed porous structure unit featuring a specific Poisson’s ratio in an arrayed 3D force sensor.
A carbon nanotube x-ray source array designed for a new multisource cone beam computed tomography scanner
Authors: Li Boyuan , Inscoe Christina R , Xu Shuang , Capo Timothy , Tyndall Donald A , Lee Yueh Z , Lu Jianping , Zhou Otto
Published: March 2024

Cone beam computed tomography (CBCT) is known to suffer from strong scatter and cone beam artifacts. The purpose of this study is to develop and characterize a rapidly scanning carbon nanotube (CNT) field emission x-ray source array to enable a multisource CBCT (ms-CBCT) image acquisition scheme which has been demonstrated to overcome these limitations. A CNT x-ray source array with eight evenly spaced focal spots was designed and fabricated for a medium field of view ms-CBCT for maxillofacial imaging. An external multisource collimator was used to confine the radiation from each focal spot to a narrow cone angle. For ms-CBCT imaging, the array was placed in the axial direction and rapidly scanned while rotating continuously around the object with a flat panel detector. The x-ray beam profile, temporal and spatial resolutions, energy and dose rate were characterized and evaluated for maxillofacial imaging. The CNT x-ray source array achieved a consistent focal spot size of 1.10 ± 0.04 mm × 0.84 ± 0.03 mm and individual beam cone angle of 2.4°

±

0.08 after collimation. The x-ray beams were rapidly switched with a rising and damping times of 0.21 ms and 0.19 ms, respectively. Under the designed operating condition of 110 kVp and 15 mA, a dose rate of 8245 μGy s−1 was obtained at the detector surface with the inherent Al filtration and 2312 μGy s−1 with an additional 0.3 mm Cu filter. There was negligible change of the x-ray dose rate over many operating cycles. A ms-CBCT scan of an adult head phantom was completed in 14.4 s total exposure time for the imaging dose in the range of that of a clinical CBCT scanner. A spatially distributed CNT x-ray source array was designed and fabricated. It has enabled a new multisource CBCT to overcome some of the main inherent limitations of the conventional CBCT.
First experimental time-of-flight-based proton radiography using low gain avalanche diodes
Authors: Ulrich-Pur Felix , Bergauer Thomas , Galatyuk Tetyana , Hirtl Albert , Kausel Matthias , Kedych Vadym , Kis Mladen , Kozymka Yevhen , Krüger Wilhelm , Linev Sergey , Michel Jan , Pietraszko Jerzy , Rost Adrian , Schmidt Christian Joachim , Träger Michael , Traxler Michael
Published: March 2024

Objective. Ion computed tomography (iCT) is an imaging modality for the direct determination of the relative stopping power (RSP) distribution within a patient’s body. Usually, this is done by estimating the path and energy loss of ions traversing the scanned volume utilising a tracking system and a separate residual energy detector. This study, on the other hand, introduces the first experimental study of a novel iCT approach based on time-of-flight (TOF) measurements, the so-called Sandwich TOF-iCT concept, which in contrast to any other iCT systems, does not require a residual energy detector for the RSP determination. Approach. A small Sandwich TOF-iCT demonstrator was built based on low gain avalanche diodes (LGADs), which are 4D-tracking detectors that allow to simultaneously measure the particle position and time-of-arrival with a precision better than 100 μm and 100 ps, respectively. Using this demonstrator, the material and energy-dependent TOF was measured for several homogeneous PMMA slabs in order to calibrate the acquired TOF against the corresponding water equivalent thickness (WET). With this calibration, two proton radiographs (pRads) of a small aluminium stair phantom were recorded at MedAustron using 83 MeV and 100.4 MeV protons. Main results. Due to the simplified WET calibration models used in this very first experimental study of this novel approach, the difference between the measured and theoretical WET ranged between 37.09% and 51.12%. Nevertheless, the first TOF-based pRad was successfully recorded showing that LGADs are suitable detector candidates for Sandwich TOF-iCT. Significance. While the system parameters and WET estimation algorithms require further optimization, this work was an important first step to realize Sandwich TOF-iCT. Due to its compact and cost-efficient design, Sandwich TOF-iCT has the potential to make iCT more feasible and attractive for clinical application, which, eventually, could enhance the treatment planning quality.
Molecular optomechanics in the anharmonic regime: from nonclassical mechanical states to mechanical lasing
Authors: Schmidt Mikołaj K , Steel M J
Published: March 2024

Cavity optomechanics aims to establish optical control over vibrations of nanoscale mechanical systems, to heat, cool or to drive them toward coherent, or nonclassical states. This field was recently extended to encompass molecular optomechanics: the dynamics of THz molecular vibrations coupled to the optical fields of lossy cavities via Raman transitions. The molecular platform should prove suitable for demonstrating more sophisticated optomechanical effects, including engineering of nonclassical mechanical states, or inducing coherent molecular vibrations. We propose two schemes for implementing these effects, exploiting the strong intrinsic anharmonicities of molecular vibrations. First, to prepare a nonclassical mechanical state, we propose an incoherent analogue of the mechanical blockade, in which the molecular anharmonicity and optical response of hybrid cavities isolate the two lowest-energy vibrational states. Secondly, we show that for a strongly driven optomechanical system, the anharmonicity can suppress the mechanical amplification, shifting and reshaping the onset of coherent mechanical oscillations. Our estimates indicate that both effects should be within reach of existing platforms for Surface Enhanced Raman Scattering.
Development of a quad-channel high-resolution digital picoammeter for beam diagnostics
Authors: Donatti M.M. , Cardoso F.H. , Tanio L.Y.
Published: March 2024

In synchrotron light source applications, the photon beam interaction with various materials can produce electric charge which can be measured as current and be used to diagnose particle trajectories, beam intensity, beam profile, position, and stability. Sirius, a 4th-generation Brazilian synchrotron light source, will make use of hundreds of low-intensity measurement instruments. This work aims to show and discuss the design details, challenges, and test results of an Ethernet four-channel high-performance digital ammeter, applied for general-purpose beam diagnostics. The device is based on low-noise and extremely low input bias bipolar transimpedance amplifiers with eight selectable ranges (full scales from pA to mA). Characterization results show that the achieved gain, accuracy, and noise performance are on the same order of magnitude as those of expensive commercial benchtop equipment. In low bandwidth applications, the device was able to measure amplitudes of hundreds of picoampere with intrinsic noise of units of femtoampere (RMS). The designed device is a cost-effective solution.
Testing a Neural Network for Anomaly Detection in the CMS Global
Trigger Test Crate during Run 3
Authors: Zipper Noah ,   the CMS collaboration
Published: March 2024

We present the deployment and testing of an autoencoder trained for unbiased detection of
new physics signatures in the CMS Level-1 Global Trigger (GT) test crate during LHC Run 3. The GT
test crate is a copy of the main GT system, receiving the same input data, but whose output is not
used to trigger the readout of CMS, providing a platform for thorough testing of new trigger
algorithms on live data, but without interrupting data taking. We describe the integration of the
Neural Network into the GT test crate, and the monitoring, testing, and validation of the
algorithm during proton collisions.
Transition path theory for diffusive search with stochastic resetting
Authors: Bressloff Paul C
Published: March 2024

Many chemical reactions can be formulated in terms of particle diffusion in a complex energy landscape. Transition path theory (TPT) is a theoretical framework for describing the direct (reaction) pathways from reactant to product states within this energy landscape, and calculating the effective reaction rate. It is now the standard method for analyzing rare events between long lived states. In this paper, we consider a completely different application of TPT, namely, a dual-aspect diffusive search process in which a particle alternates between collecting cargo from a source domain A and then delivering it to a target domain B. The rate of resource accumulation at the target, k

AB
, is determined by the statistics of direct (reactive or transport) paths from A to B. Rather than considering diffusion in a complex energy landscape, we focus on pure diffusion with stochastic resetting. Resetting introduces two non-trivial problems in the application of TPT. First, the process is not time-reversal invariant, which is reflected by the fact that there exists a unique non-equilibrium stationary state (NESS). Second, calculating k

AB
involves determining the total probability flux of direct transport paths across a dividing surface S between A and B. This requires taking into account discontinuous jumps across S due to resetting. We derive a general expression for k

AB
and show that it is independent of the choice of dividing surface. Finally, using the example of diffusion in a finite interval, we show that there exists an optimal resetting rate at which k

AB
is maximized. We explore how this feature depends on model parameters.