bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures
Authors: Aravind Indu , Wang Yu , Cai Zhi , Li Ruoxi , Shahriar Rifat , Gibson George N. , Guignon Ernest , Cady Nathaniel C. , Page William D. , Pilar Arturo , Cronin Stephen B.
Published: July 2024

We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode–solution interfaces.
From L-mode to the L–H transition, experiments on ASDEX upgrade and related gyrokinetic simulations
Authors: Bonanomi N. , Angioni C. , Conway G. D. , Happel T. , Plank U. , Schneider P. A. , Staebler G. M. ,   ASDEX Upgrade Team,   EUROFusion MST1 Team
Published: July 2024

This work combines experimental observations from the ASDEX Upgrade tokamak with related gyrokinetic simulations of the turbulence moving from L-mode toward, and beyond, the L–H transition. Dedicated experiments have been performed with slow steps of increasing electron cyclotron heating power. Gyrokinetic simulations of the edge turbulence of these plasmas highlight the key roles of the non-linear electromagnetic effects and the external flow shear (E × B shear), both related to the evolution of the plasma pressure profile with increasing heating power. The increase in the plasma βe destabilizes turbulence at low toroidal mode numbers, that, in turn, is strongly suppressed by the external flow shear. This allows the plasma pressure profiles to evolve without a sharp rise in the turbulent fluxes. When all the experimentally measured plasma parameters are consistently included as inputs of the local gyrokinetic simulations, both the experimental electron and ion heat fluxes are quantitatively reproduced on the whole L-mode phase of the selected discharge. Simulations carried out with edge parameters of an ELM-free H-mode phase still show the importance of the mechanisms discussed earlier while also indicating possible limitations of the local approach.
Ultrafast photochemistry and electron diffraction for cyclobutanone in the S2 state: Surface hopping with time-dependent density functional theory
Authors: Miller Ericka Roy , Hoehn Sean J. , Kumar Abhijith , Jiang Dehua , Parker Shane M.
Published: July 2024

We simulate the photodynamics of gas-phase cyclobutanone excited to the S2 state using fewest switches surface hopping (FSSH) dynamics powered by time-dependent density functional theory (TDDFT). We predict a total photoproduct yield of 8%, with a C3:C2 product ratio of 0 trajectories to 8 trajectories. One primary S2 → S1 conical intersection is identified involving the compression of an α-carbon–carbon–hydrogen bond angle. Excited state lifetimes computed with respect to electronic state populations were found to be 3.96 ps (S2 → S1) and 498 fs (S1 → S0). We also generate time-resolved difference pair distribution functions (ΔPDFs) from our TDDFT-FSSH dynamics results in order to generate direct comparisons with ultrafast electron diffraction experiment observables. Global and target analysis of time-resolved ΔPDFs produced a distinct set of lifetimes: (i) a 0.548 ps decay and (ii) a 1.69 ps decay, both resembling the S2 minimum, as well as (iii) a long decay that resembles the S1 minimum geometry and the fully separated C2 products. Finally, we contextualize our results by considering the impact of the most likely sources of significant errors.
Photon-assisted electron depopulation of 4H-SiC/SiO2 interface states in n-channel 4H-SiC metal–oxide–semiconductor field effect transistors
Authors: Weger M. , Kuegler J. , Nelhiebel M. , Moser M. , Bockstedte M. , Pobegen G.
Published: July 2024

4H-SiC/SiO2 interface states play a major role in the performance and reliability of modern 4H-SiC metal–oxide–semiconductor field effect transistors (MOSFETs). To gain new insights into these interface states, we developed a cryogenic measurement technique that uses photon-assisted electron depopulation to probe device performance limiting 4H-SiC/SiO2 interface states. This technique enables the characterization of shallow as well as deep states at the 4H-SiC/SiO2 interface of fully processed devices using a cryogenic probe station. Our method is performed on n-channel 4H-SiC MOSFET test structures with deposited oxide and postoxidation anneal. We identify conditions under which the electrons remain trapped at 4H-SiC/SiO2 interface states and trigger the controlled photon-assisted electron depopulation within a range of photon energies. This allows us to prove the presence of near interface traps, which have previously been found in thermally grown 4H-SiC MOS structures. Our results are supported by device simulations. Additionally, we study the impact of irradiation intensity and light exposure time on the photon-induced processes.
Localized surface plasmon energy dissipation in bimetallic core–shell nanostructures
Authors: Sang Lixia , Ren Zhiyong , Zhao Yue
Published: July 2024

Exploring the plasmon energy dissipation mechanism of bimetallic nanostructures after photoexcitation is of great significance for controlling energy transfer in plasmonic applications. The absorption, scattering, and extinction spectra of Ag@Cu, Ag@Pt, and Ag@Co core–shell nanostructures are calculated by finite element method, and the energy dissipation process is visualized by using particle trajectory and the absorbed power density distribution. The absorption/scattering ratio of the core–shell nanostructures, the shell absorptivity, the time-domain electric field as well as the extra-core electron arrangements of Ag, Cu, Pt, and Co atoms are analyzed for figuring out the energy dissipation mechanism. The results show that when a non-plasmonic metal is coated on the surface of a plasmonic metal, the plasmon energy dissipates preferentially in the shell, and the degree of dissipation depends on the imaginary part of the dielectric constant of the shell and the core. A larger dielectric constant of the shell can cause more energy to be transferred from the plasmonic metal to the shell region. This study provides the fundamental physical framework and design principles for plasmonic nanostructures.
Resonance Raman intensity analysis of photoactive metal-organic frameworks
Authors: Brennan Joe , Choi Tae Hoon , Soilis Zoe M. , Rosi Nathaniel L. , Johnson J. Karl , Frontiera Renee
Published: July 2024

Metal-organic frameworks (MOFs) are promising candidate materials for photo-driven processes. Their crystalline and tunable structure makes them well-suited for placing photoactive molecules at controlled distances and orientations that support processes such as light harvesting and photocatalysis. In order to optimize their performance, it is important to understand how these molecules evolve shortly after photoexcitation. Here, we use resonance Raman intensity analysis (RRIA) to quantify the excited state nuclear distortions of four modified UiO-68 MOFs. We find that stretching vibrations localized on the central ring within the terphenyl linker are most distorted upon interaction with light. We use a combined computational and experimental approach to create a picture of the early excited state structure of the MOFs upon photoactivation. Overall, we show that RRIA is an effective method to probe the excited state structure of photoactive MOFs and can guide the synthesis and optimization of photoactive designs.
Identification of the conductivity type of single-walled carbon nanotubes via dual-modulation dielectric force microscopy
Authors: Lai Junqi , Wang Wenyuan , Liu Shuai , Chen Bowen , Kang Lixing , Chen Qi , Chen Liwei
Published: July 2024

The conductivity type is one of the most fundamental transport properties of semiconductors, which is usually identified by fabricating the field-effect transistor, the Hall-effect device, etc. However, it is challenging to obtain an Ohmic contact if the sample is down to nanometer-scale because of the small size and intrinsic heterogeneity. Noncontact dielectric force microscopy (DFM) can identify the conductivity type of the sample by applying a DC gate voltage to the tip, which is effective in tuning the accumulation or depletion of charge carriers. Here, we further developed a dual-modulation DFM, which simplified the conductivity type identification from multiple scan times under different DC gate voltages to a single scan under an AC gate voltage. Taking single-walled carbon nanotubes as testing samples, the semiconducting-type sample exhibits a more significant charge carrier accumulation/depletion under each half-period of the AC gate voltage than the metallic-type sample due to the stronger rectification effect. The charge carrier accumulation or depletion of the p-type sample is opposite to that of the n-type sample at the same half-period of the AC gate voltage because of the reversed charge carrier type.
Modeling temperature-dependent transport properties in dissipative particle dynamics: A top-down coarse-graining toward realistic dynamics at the mesoscale
Authors: Lauriello N. , Lísal M. , Boccardo G. , Marchisio D. , Buffo A.
Published: July 2024

Dissipative particle dynamics (DPD) is a widespread computational tool to simulate the behavior of soft matter and liquids in and out of equilibrium. Although there are many applications in which the effect of temperature is relevant, most of the DPD studies have been carried out at a fixed system temperature. Therefore, this work investigates how to incorporate the effect of system temperature variation within the DPD model to capture realistic temperature-dependent system properties. In particular, this work focuses on the relationship between temperature and transport properties, and therefore, an extended DPD model for transport properties prediction is employed. Transport properties, unlike the equilibrium properties, are often overlooked despite their significant influence on the flow dynamics of non-isothermal mesoscopic systems. Moreover, before simulating the response of the system induced by a temperature change, it is important to first estimate transport properties at a certain temperature. Thus here, the same fluid is simulated across different temperature conditions using isothermal DPD with the aim to identify a temperature-dependent parametrization methodology, capable of ensuring the correctness of both equilibrium and dynamical properties. Liquid water is used as a model system for these analyses. This work proposes a temperature-dependent form of the extended DPD model where both conservative and non-conservative interaction parameters incorporate the variation of the temperature. The predictions provided by our simulations are in excellent agreement with experimental data.
Impact of photovoltaic power generation on poverty alleviation in Jiangsu, China
Authors: Li Wenbo , Huang Jiaxin , Kong LingJing , Liang Dongzhen
Published: July 2024

The photovoltaic poverty alleviation project, part of the “Ten Major Precise Poverty Alleviation Projects” implemented by the Poverty Alleviation Office of the State Council, significantly contributes to eradicating poverty and rural revitalization. A difference-in-differences model was utilized in this study to assess this project's impact on rural households. This analysis used tracking data from households both with photovoltaic equipment installed and without in “S Town,” Jiangsu Province, from 2017 to 2021. The results indicate that photovoltaic installations lead to an increase in per capita disposable income, hence reducing poverty. However, further analysis suggests that better health and work capacity in disadvantaged households correlate with lesser benefits from the photovoltaic project in terms of income. The policy implications of these findings include a necessity for developing innovative models in the photovoltaic sector to enhance conditions for farmers, reducing their dependence on government subsidies.
High-finesse nanofiber Fabry–Pérot resonator in a portable storage container
Authors: Horikawa S. , Yang S. , Tanaka T. , Aoki T. , Kato S.
Published: July 2024

We present characterization and storage methods for a high-finesse nanofiber Fabry–Pérot resonator. Reflection spectroscopy from both ends of the resonator allows for the evaluation of the mirror transmittances and optical loss inside the resonator. To maintain the quality of the nanofiber resonator after the fabrication, we have developed a portable storage container. By filling the container with dry, clean nitrogen gas, we can prevent contamination of the nanofiber during storage. This approach allows us to minimize the additional optical loss to less than 0.08% over a week. The portable container facilitates both the fabrication and subsequent experimentation with the resonator in different locations. This flexibility expands the range of applications, including quantum optics, communication, and sensing.
Assessing rural energy poverty and early warning based on long-run evolution for clean energy transition in China
Authors: Yin Shi , Wang Man , Shi Yaqi , Zhao Yumeng
Published: July 2024

Rural China grapples with pervasive energy poverty. This study aims to measure China's rural energy poverty and propose early warning strategies. It establishes a rural energy relative poverty evaluation system based on four dimensions: energy service effectiveness, consumption cleanliness, management integrity, and development sustainability. Using the Analytic Hierarchy Process-Criteria Importance Though Intercriteria Correlation-Technique for Order Preference by Similarity to Ideal Solution model, it calculates rural energy poverty indices for Chinese provinces, while ward cluster analysis sets regional and hierarchical early warning criteria. Findings indicate: (1) China's rural energy poverty index varies widely, with a low range of 0.49–0.52 and a high range above 0.65. The top 14 regions average a rural energy poverty index of 0.62. (2) Over 2015–2021, there is a 9.70% decrease in the index, indicating a general downward trend. While rural energy services' efficiency and management integrity improve, consumption cleanliness and development sustainability decline. (3) Spatially, energy poverty is higher in the west and north, notably lower in the east and south. The eastern coastal and central regions exhibit significantly lower poverty levels due to better economic foundations and leading energy transformations. (4) Nine provinces are red warning areas, witnessing declining sustainability but improving service effectiveness, consumption cleanliness, and management integrity. Weak links in energy poverty vary across regions in terms of service effectiveness, consumption cleanliness, management integrity, and development sustainability. This study enhances the rural energy poverty evaluation system and proposes regional, hierarchical, and phased early warning standards.
2D MnTiX2 (X = F/Cl/Br) monolayers: Robust valley-polarized quantum anomalous Hall insulators with high transition temperatures and wide bandgaps
Authors: Duan Yuanyuan , Xu Xiaokang , Mao Yuqing , Niu Xianghong , Lian Huijie , Yao Xiaojing , Lu Jinlian , He Ailei , Liu Yongjun , Zhang Xiuyun
Published: July 2024

The valley-polarized quantum anomalous Hall (VP-QAH) materials, which combine valley polarization and the quantum anomalous Hall (QAH) effect, are of both fundamental and technological importance due to their potential applications for nanoscale devices. Here, we explored the stability, magnetic, and topological properties of two-dimensional MnTiX2 (X = F/Cl/Br) monolayers based on first-principles calculations. Our results show that all the structures have robust antiferromagnetic orders with large magnetic anisotropic energies and high transition temperatures (480–670 K). In the absence of spin–orbital coupling (SOC), the MnTiX2 monolayers represent antiferromagnetic quadratic crossing semimetals. In the presence of SOC, the quadratic crossing points of the systems are opened with sizable bandgaps (> 0.5 eV), and they are transformed to be QAH insulators with |C| = 1. Moreover, the MnTiF2 monolayer is found to be a spontaneous VP-QAH semiconductor due to the time reversal symmetry and inversion symmetry being broken. These insights provide an ideal platform for achieving VP-QAH materials for dissipationless transport and quantum computing.
Flow past two diamond-section cylinders in tandem arrangement at a low Reynolds number
Authors: Mishra Shravan Kumar , Sen Subhankar
Published: July 2024

The unsteady flow surrounding two fixed diamond cylinders is analyzed at Reynolds number 100 over normalized center-to-center spacing ratios 2−15. By analyzing the contours of instantaneous vorticity, variations of recirculation length, surface pressure, and fluid forcing of cylinders, the value of normalized critical spacing is found to be 3.4. In the reattachment zone below critical spacing, vortex-shedding from the upstream (UC) and downstream (DC) cylinders is anti-phase. At the critical spacing, regular vortex-shedding commences also from the UC, and vortex-shedding from the cylinders becomes phase synchronized for the first time. The analysis of a vortex-shedding cycle at the critical spacing reveals that the cylinders shed vortices at the same frequency, but with a time delay. Impingement of vortices shed from the UC on the DC strengthens vorticity around the DC and shifts the instantaneous position of its forward stagnation point from the leading edge. The understanding that locations of stagnation points govern the direction and magnitude of lift force comes from the analysis of flow at the critical gap. When the surface bounded by stagnation points is occupied mostly with negative vorticity, the instantaneous lift is negative and vice versa. At critical spacing, mean streamlines show the emergence of an anti-wake at forward stagnation point of the DC for the first time. Over the entire range of cylinder separation, nine distinct patterns of separation topologies are identified. Below critical spacing, both pressure and viscous drag components, and hence, total drag of the DC are negative or upstream-acting.
Field-free switching of perpendicular magnetic elements by using two orthogonal sub-nanosecond spin–orbit torque pulses
Authors: Suess Dieter , Abert Claas , Zeilinger Sebastian , Bruckner Florian , Koraltan Sabri
Published: July 2024

We propose a field-free switching mechanism that utilizes two spatially orthogonal spin–orbit torque (SOT) currents. Initially applied simultaneously, one of the currents is subsequently switched off. The superposition of these two currents results in an in-plane magnetization, which is not orthogonal to the remaining SOT current after the second one is deactivated. This symmetry-breaking procedure leads to reproducible and rapid switching, with field pulse durations as short as 0.25 ns.
Quantification of the strong, phonon-induced Urbach tails in β-Ga2O3 and their implications on electrical breakdown
Authors: Islam Ariful , Rock Nathan David , Scarpulla Michael A.
Published: July 2024

In ultrawide bandgap (UWBG) nitride and oxide semiconductors, increased bandgap (Eg) correlates with greater ionicity and strong electron–phonon coupling. This limits mobility through phonon scattering, localizes carriers via polarons and self-trapping, broadens optical transitions via dynamic disorder, and modifies the breakdown field. Herein, we use polarized optical transmission spectroscopy from 77 to 633 K to investigate the Urbach energy (Eu) for many orientations of Fe- and Sn-doped β-Ga2O3 bulk crystals. We find Eu values ranging from 60 to 140 meV at 293 K and that static (structural defects plus zero-point phonons) disorder contributes more to Eu than dynamic (finite temperature phonon-induced) disorder. This is evidenced by lack of systematic Eu anisotropy, and Eu correlating more with x-ray diffraction rocking-curve broadening than with Sn-doping. The lowest measured Eu are ∼10× larger than for traditional semiconductors, pointing out that band tail effects need to be carefully considered in these materials for high field electronics. We demonstrate that, because optical transmission through thick samples is sensitive to sub-gap absorption, the commonly used Tauc extraction of a bandgap from transmission through Ga2O3 >1–3 μm thick is subject to errors. Combining our Eu(T) from Fe-doped samples with Eg(T) from ellipsometry, we extract a measure of an effective electron–phonon coupling that increases in weighted second order deformation potential with temperature and a larger value for E||b than E||c. The large electron–phonon coupling in β-Ga2O3 suggests that theories of electrical breakdown for traditional semiconductors need expansion to account not just for lower scattering time but also for impact ionization thresholds fluctuating in both time and space.
Calculation of toroidal Alfvén eigenmode mode structure in general axisymmetric toroidal geometry
Authors: Wei Guangyu , Falessi Matteo Valerio , Wang Tao , Zonca Fulvio , Qiu Zhiyong
Published: July 2024

A workflow is developed based on the ideal MHD model to investigate the linear physics of various Alfvén eigenmodes in general axisymmetric toroidal geometry by solving the coupled shear Alfvén wave (SAW) and ion sound wave (ISW) equations in ballooning space. The model equations are solved by the FALCON code in the singular layer, and the corresponding solutions are then taken as the boundary conditions for calculating parallel mode structures in the whole ballooning space. As an application of the code, the frequencies and mode structures of toroidal Alfvén eigenmode (TAE) are calculated in the reference equilibria of the Divertor Tokamak Test facility with positive and negative triangularities, respectively. As typical result for reactor relevant plasma conditions, which are strongly triangular in the outer core region where magnetic shear is of order unity, we show that the triangularity effect on TAE is generally small. Furthermore, by properly handling the boundary conditions, we demonstrate finite TAE damping due to coupling with the local acoustic continuum and find that the damping rate is small for typical plasma parameters.
Numerical analysis of three-dimensional magnetopause-like reconnection properties by Hall MHD simulation for SPERF-AREX
Authors: He Xianglei , Mao Aohua , Apatenkov Sergey , Zhang Zhonglin , Wang Zhibin , Sun Mengmeng , Zou Jitong , Wang Xiaogang
Published: July 2024

The ground-based device, the Space Plasma Environment Research Facility (SPERF), is established for experimentally simulating magnetosphere plasma processes, with one of its major components, asymmetric reconnection experiment (AREX), for three-dimensional physics relevant to dayside asymmetric magnetopause reconnection. As an outstanding property of fast magnetic reconnection in collisionless plasmas, the Hall effect and its geometric features can be experimentally investigated in SPERF-AREX with various magnetic configurations related to different driven scenarios for simulating interplanetary magnetic field (IMF) conditions. In this work, the Hall effect and its geometric characteristics in such proposed experiments are numerically studied based on a Hall MHD model. The simulation results reveal that in the X-line geometry relevant to southward IMFs, the Hall field features in cross section perpendicular to the X-line are mostly analogous to typical two-dimensional Hall quadrupole structures, clearly an “anti-parallel reconnection” feature. In the separator (A-B null-line) geometry relevant to arbitrary IMF orientations, along the separator between magnetic nulls, the magnetic field configuration near a magnetic null also demonstrates the typical quadrupolar pattern. However, the pattern is distorted away (>10di, here di=c/ωpi is the ion inertial length) from the nulls, in a way similar to that in “component reconnection.” Furthermore, the Hall effect induces a dawn-dusk asymmetry for both the X-line and the separator geometries.
Screened optimally tuned range separated hybrid functional for solvated low bandgap molecular systems
Authors: Dantas Filho Reinaldo V. , de Queiroz Thiago B.
Published: July 2024

The description of electronic properties of low bandgap molecular system is often performed by using density functional theory (DFT) and time dependent (TD) DFT calculations with the optimally tuned range-separated hybrid (OT-RSH) functional, as it contains the necessary ingredients to reliably predict charge transfer excitations. However, the range separating parameter (ω) is system-dependent and its optimization, including the chemical environment, is intricate. Refaely-Abramson et al. demonstrated that the gap renormalization in molecular crystals, a ground state property, can be represented by an OT-RSH functional screened by ɛstatic [Phys. Rev. B 88, 081204(R) (2013)], the zero frequency scalar dielectric constant. In this study, we propose the use of an OT-RSH functional screened by the scalar dielectric constant in the high frequency limit (OT-sRSH), ɛ∞, an appropriate constraint for vertical ionization energies or excitations in a dielectric environment. We have performed calculations for S,N-heteroacene derivatives in tetrahydrofuran and dichloromethane. The “unscreened” OT-RSH functional tends to underestimate experimental ionization potentials (IPs) and optical gaps (Egs) by up to 1.5 and 0.5 eV, respectively. In contrast, OT-sRSH functional calculations underestimate IPs and Egs by only 0.4 and 0.2 eV. We also compared the OT-sRSH results to explicitly solvated OT-RSH functional calculations for oligothiophenes in dioxane, benzene in ammonia, and methylene blue in water. We observe that both the approaches perform similarly for weakly interacting intermolecular systems and deviate for solvent–solute interacting systems, as expected. In conclusion, the OT-sRSH functional can describe molecular systems with environmental polarization effects accurately, a step toward describing realistic molecular systems.
Numerical study on piezoelectric inkjet with liquid compressibility
Authors: Kim San , Sohn Dong Kee , Ko Han Seo
Published: July 2024

A two-dimensional numerical model for a cylindrical piezoelectric inkjet was developed to analyze the ink droplet formation and meniscus behavior, considering the ink compressibility. The propagation of the acoustic pressure wave, which was generated by the piezo actuator, could be simulated by considering the compressibility of the ink. The volume of fluid method was employed for multiphase flow, while the dynamic mesh method was used to implement the piezo actuation. In this study, the key operational parameters of operating voltage, compressibility of working fluid, dwell time of waveform, contact angle, and restrictor dimensions were varied to conduct a comprehensive parametric analysis. The underlying mechanism governing droplet formation could be identified through the analysis of the propagation of successive acoustic pressure waves. Furthermore, the volume fraction and mass flow rate results were used to analyze the jetting performances quantitatively and qualitatively. The mass flow rate results were used to determine the implicit effect of physical properties, such as the viscosity and surface tension, through momentum analysis. The developed model including ink compressibility accurately predicted the behavior of the inkjet jetting and the meniscus motion. In addition, it allows visualization of the internal flow structure and optimization of operating conditions to increase the stability and productivity of inkjet printing.
Distinct CO2-run-out regime from steric effect of electric double layer in electrochemical CO2 reduction
Authors: Chen Longfei , Feng Hao , Zhang Ying , Liu Dong , Li Qiang
Published: July 2024

The field of electrochemical CO2 reduction reaction (eCO2RR) is pursuing high operating current densities, eventually controlled by CO2 transport. Here, we develop a new multiscale modeling approach that is able to more generally describe the effects of the electric double layer (EDL) on CO2 transport over a wide potential window extending to utmost potentials. By leveraging it, we identify a distinct CO2-run-out regime where the supply of CO2 runs out due to the EDL steric effect from a dense layer of solvated cations with the maximum layer thickness equal to the solvated cation size. Consequently, CO2RR current density drops at a relatively negative transition potential generating a bell-shaped polarization curve, which is in contrast to the CO2-transport-limited regime where the current density reaches a plateau. Furthermore, we develop a graphical method, verified by experimental data, to generally predict the transition to the CO2-run-out regime. This work sheds new light on the EDL effects for catalyst design and electrolyzer engineering.
Similarity solution for the magnetogasdynamic shock wave in a self-gravitating and rotating ideal gas under the influence of radiation heat flux
Authors: Vats Vidit Kumar , Singh Dheerendra Bahadur , Manjul Mrigendra
Published: July 2024

The Lie invariance method is used to analyze the one-dimensional, unsteady flow of a cylindrical shock wave in a rotating, self-gravitating, radiating ideal gas under the influence of an axial or azimuthal magnetic field, with an emphasis on adiabatic conditions. The analysis assumes a stationary environment just ahead of the shock wave and considers variations in fluid velocity, magnetic field, and density within the perturbed medium just behind the shock front. In the governing equations, the impact of thermal radiation under an optically thin limit is integrated into the energy equation. Utilizing the Lie invariance method, the set of partial differential equations governing the flow in this medium is transformed into a system of nonlinear ordinary differential equations (ODEs) using similarity variables. Two distinct cases of similarity solutions are obtained by selecting different values for the arbitrary constants associated with the generators. Among these cases, one yields similarity solutions assuming a power-law shock path and the other an exponential-law shock path. For both cases, the resulting set of nonlinear ODEs are numerically solved using the 4th-order Runge–Kutta method in MATLAB software. The article thoroughly explores the influence of various parameters, including γ (adiabatic index of the gas), Ma−2 (Alfvén–Mach number), σ (ambient density exponent), l1 (rotational parameter), and G0 (gravitational parameter) on the flow properties. The findings are visually presented to offer a comprehensive insight into the effects of these parameters.
Motion behaviors of droplets containing Au nanoparticles on a superhydrophobic laser-induced graphene surface
Authors: Han Yunrui , Fan Guangpeng , Han Yingkuan , Zhang Yu , Huang Ning , Wen Mingda , Han Lin
Published: July 2024

The movement of nanoparticle-containing droplets on solid surfaces significantly affects the distribution of the nanoparticles and is of great interest in the fields of two-phase separation, biosensing detection, inkjet printing, and microarrays. There has been little research on the initiation and motion behaviors of colloidal droplets containing nanoparticles on superhydrophobic surfaces. Here, we prepare superhydrophobic laser-induced graphene (LIG) surfaces with excellent depinning effects using an extremely simple method and explore the formation mechanism of the depinning-LIG surfaces. The reduction of nano-graphene fibers and the increased hydroxyl group ratio after alcohol modification further enhance the hydrophobic properties of depinning-LIG, reducing its surface adhesion. The initial and continuous motion of droplets containing Au nanoparticles (AuNPs) on these superhydrophobic surfaces under airflow is studied using high-speed microscopy. The coupling effects of the droplet size, surface properties, airflow velocity, and nanoparticles on the droplet motion behaviors are analyzed. The dimensionless parameter G is incorporated to obtain the partition diagram of AuNP droplet motion behaviors on depinning-LIG surfaces, which delineate the critical conditions for droplet “oscillation,” “initiate sliding,” and “continuous rolling” as a function of system parameters. For AuNP droplets, the viscous force Fγ,p exerted by the nanoparticles on the contact line significantly affects the droplet movement behaviors. In addition, a mathematical model about the competition of dynamic forces and resistance is established to describe the motion of AuNP droplets, and the critical conditions for different motion behaviors of the droplet are clarified to guide practical applications.
Temperature dependent Raman spectroscopy and sensing performance of 2D black phosphorus
Authors: Chen Jiangtao , Wang Xinyi , Song Tiancheng , Wang Ting , Ma Guobin , Zhang Xuqiang , Zhao Yun , Chen Jianbiao , Yang Bingjun , Li Yan
Published: July 2024

Temperature is an important parameter to be monitored in new wearable electronic devices. Layered black phosphorus (BP) has inherent good thermal stability and semiconductor properties and has a promising application as a temperature sensing layer. Here, we investigate the temperature sensing properties of BP, using in situ Raman spectroscopy and x-ray diffraction techniques. Flexible sensors are constructed, and temperature response is investigated in the range of 6–38 °C. The prospect application for monitoring the temperature of human body parts is demonstrated. The results show that the BP-based temperature sensors demonstrate good negative temperature coefficient characteristics and display high sensitivity and reproducible sensing performance. The temperature-dependent performance suggests the feasibility of BP as a sensitive layer in a wide temperature range. This work paves the way for exploring new applications of amazing layered materials, such as BP, in wearable electronic devices.
Rapid-scan broadband frequency-domain terahertz spectroscopy via dynamic optical phase lock
Authors: Shoji Yuto , Ohmichi Eiji , Takahashi Hideyuki , Ohta Hitoshi
Published: July 2024

Frequency-domain terahertz (THz) spectroscopy using photomixing devices has unique advantages such as high dynamic range and high spectral resolution. Thus, many applications for solid-state and gas-phase spectroscopy have been proposed. In this study, we developed a feedback controlled technique to dynamically compensate for the optical phase accompanied by frequency sweep, enabling both fast and high-resolution data acquisition across a wide frequency region. From gas-phase THz spectroscopy measurements of dilute acetonitrile gas in a wide frequency range up to 1.1 THz, fine structures with linewidths less than 10 MHz were clearly resolved, while the data acquisition rate was improved by two orders compared to the previously reported value.
The ion-activated attractive patchy particle model and its application to the liquid–vapor phase transitions
Authors: Surfaro Furio , Zhang Fajun , Schreiber Frank , Roth Roland
Published: July 2024

Patchy particles are an intriguing subject of study and indeed a model system in the field of soft matter physics. In recent years, patchy particle models have been applied to describe a wide variety of systems, including colloidal crystals, macromolecular interactions, liquid crystals, and nanoparticle assemblies. Given the importance of the topic, rationalizing and capturing the basic features of these models is crucial to their correct application in specific systems. In this study, we extend the ion-activated attractive patchy particles model previously employed to elucidate the phase behavior of protein solutions in the presence of trivalent salts. Our extension incorporates the effect of repulsion between unoccupied and occupied binding sites, depicted as patches. Furthermore, we examine the influence of model parameters on the liquid–vapor coexistence region within the phase diagram, employing numerical methods. A deeper understanding of this model will facilitate a better comprehension of the effects observed in experiments.
Onset and growth of viscous fingering in miscible annular ring
Authors: Hong Joung Sook , Palodhi Lopamudra , Mishra Manoranjan , Kim Min Chan
Published: July 2024

We investigate the onset and growth of viscous fingering (VF) of miscible annulus in a radial Hele-Shaw cell. Systematic numerical study on a finite annulus domain is performed by employing finite element method solver in COMSOL Multiphysics software. We justify that concentration field analysis is not a good choice for dynamic study in radial flows. Instead, velocity magnitude is a better tool to understand the dynamics. Therefore, we propose velocity field analysis to better differentiate the stable and unstable states and present a new stability criterion using the velocity field method. Most interestingly, using the velocity field analysis and the new stability criterion, we show a restabilization of the VF at a critical time when the system becomes diffusion dominant and able to provide both the onset time, τon (time at which instability develops), and the time at which the interface returns to the stable state, τd. Furthermore, the study successfully suggests the critical values for several dimensionless parameters, the Péclet number (Pe), log-viscosity ratio (R), and volumetric ratio (ra) and time (τ), to induce instability. When Pe is higher than 103, the evolution of VF instability is no longer enhanced by Pe, and Rc converges to a certain value. In particular, for the transiently unstable system of low Pe, the restabilization of VF instability is identified even though R is higher than Rc. The unstable system (τ>τon) returns to the stable state as injection time increases further. Moreover, we obtained a critical value of the volumetric ratio (rc,a).
A modular, high dynamic range passive neutron dosimeter and imaging diagnostic
Authors: Schmidt T. R. , Dwyer R. H. , Broughton D. P. , Hochanadel M. P. , Batha S. H.
Published: July 2024

The multi-decade neutron dosimeter and imaging diagnostic (MDND) is a passive diagnostic that utilizes the polyethylene (n, p) nuclear reaction to enhance the diagnostic’s sensitivity for time and energy integrated neutron measurements in the range of 2.45–14.1 MeV. The MDND utilizes a combination of radiochromic film, phosphor image plates, and solid-state nuclear track detectors, with the goal of providing several orders of magnitude of dynamic range in terms of measured neutron fluence. The diagnostic design was guided by simulations in the Monte Carlo N-Particle (MCNP) transport code to determine the optimum thickness of the polyethylene convertor for maximum proton fluence incident on the detection medium as a function of incident neutron energy. In addition, the simulation results of complete diagnostic assemblies, or “stacks,” were used to determine the total dynamic range of an MDND in terms of measured neutron source yield, which was found to be between around 107 and 1015 emitted into 4π with the detector located 1 m away from the source. Complimentary to these simulations, individual detectors within a stack were simulated and analyzed to determine response as a function of neutron energy and yield. This work presents the diagnostic design, MCNP simulation results, and analysis of expected signals for varying neutron sources.
Wake-induced response of a flexible splitter plate detachedly placed downstream of a circular cylinder
Authors: Zhu Hongjun , Chen Quanyu , Zhong Jiawen , Zhang Wenxiang , Zhou Tongming
Published: July 2024

A fluid–structure interaction numerical investigation was conducted on the flow past a circular cylinder with a detached flexible plate at a low Reynolds number Re = 160. A broad gap ratio range of 0–6.0 is examined at three plate lengths. Numerical results indicated that the vortex formation is closely related to the position of the plate with respect to the recirculation region behind the cylinder. Three wake interference regimes are identified, including the extended-body, continuous reattachment (CR), and alternate reattachment (AR). Taking into account the wake interference and vortex shedding modes and the response order, six wake flow patterns are observed. The CR regime shifts to AR at a critical gap G/D = 3, where both the vibration amplitude and frequency sharply increase. The sizes of vortex spacing and plate length determine the response mode of the flexible plate. Compared to an isolated cylinder, the optimal reduction percentages in drag and lift coefficients are around 90% and 20%, respectively.
Vector substrate-based Josephson junctions
Authors: Wu Yu-Jung , Hack Martin , Wurster Katja , Koch Simon , Kleiner Reinhold , Koelle Dieter , Mannhart Jochen , Harbola Varun
Published: July 2024

We present a way to fabricate bicrystal Josephson junctions of high-Tc cuprate superconductors that are not grown on bulk bicrystalline substrates. Based on vector substrate technology, this approach makes use of a few tens-of-nanometer-thick bicrystalline membranes transferred onto conventional substrates. We demonstrate 24° [001]-tilt YBa2Cu3O7−x Josephson junctions fabricated on sapphire single crystals by utilizing 10-nm-thick bicrystalline SrTiO3 membranes. This technique allows one to manufacture bicrystalline Josephson junctions of high-Tc superconductors on a large variety of bulk substrate materials, providing distinctive degrees of freedom in designing the junctions and their electronic properties. Furthermore, it offers the capability to replace the fabrication of bulk bicrystalline substrates with thin-film growth methods.
Systematical study on the aerodynamic control mechanisms of a 1:2 rectangular cylinder with Kirigami scales
Authors: Hu Haoqi , Yang Wenhan , Meng Hao , Gao Donglai
Published: July 2024

Biomimetic flow control is being widely applied. In the present study, a biomimetic flow control method, i.e., Kirigami scales, was applied on a 1:2 rectangular cylinder. The effects of scales' shapes and pasting surfaces on the aerodynamics and circumferential flow patterns of a 1:2 rectangular cylinder were studied. Three scale shapes were investigated with different pasting methods, i.e., elliptical, circular, and triangular scales. The Reynolds number (Re) was set at 1.3–3.1 × 104. The surface pressure distributions and the integrated aerodynamic forces were further analyzed at Re = 1.3 × 104. Results show that pasting the elliptical scales on all surfaces performs best, reaching a 2.4% drag reduction and a 76.4% lift reduction. Moreover, the elliptical and triangular scales on the windward and leeward surfaces can significantly reduce the Re effect. To reveal the control mechanism, the particle image velocimetry technique was employed to obtain the circumferential and wake flow fields. The time-averaged and phase-averaged results indicate that the Kirigami scales can push the interactions of shear layers and the shedding vortices further downstream. The Proper orthogonal decomposition analysis and time-averaged turbulent kinetic energy (TKE) results indicate that the wake vortex shedding is significantly suppressed. The spanwise wake flow field was also investigated. Results show that the spanwise TKE values are significantly reduced. This study further deepened the application of Kirigami scales on the common blunt bodies.
Investigation into the impact of charging rates on the stress development within silicon composite electrodes
Authors: Li Dawei , Jiang Hainan , Li Xiaolin , Liu Jiahui , He Yaolong , Zheng Yuejiu , Zhang Junqian
Published: July 2024

Silicon, renowned for its remarkable energy density, has emerged as a focal point in the pursuit of high-energy storage solutions for the next generation. Nevertheless, silicon electrodes are known to undergo significant volume expansion during the insertion of lithium ions, leading to structural deformation and the development of internal stresses, and causing a rapid decline in battery capacity and overall lifespan. To gain deeper insights into the intricacies of charge rate effects, this study employs a combination of in situ measurements and computational modeling to elucidate the cyclic performance of composite silicon electrodes. The findings derived from the established model and curvature measurement system unveil the substantial alterations in stress and deformation as a consequence of varying charge rates. Notably, the active layer experiences compressive forces that diminish as the charge rate decreases. At a charge rate of 0.2, the active layer endures a maximum stress of 89.145 MPa, providing a comprehensive explanation for the observed deterioration in cycling performance at higher charge rates. This study not only establishes a fundamental basis for subsequent stress analyses of silicon electrodes but also lays a solid foundation for further exploration of the impact of charge rates on composite silicon electrodes.
The multi-cycle dynamics of the cavitation bubble near the solid wall with an air-entrapping hole or a hemispherical air bubble: A numerical study
Authors: Yin Jianyong , Zhang Yongxue , Ma Mingkai , Tian Lei , Du Xianrong
Published: July 2024

Investigating the interaction between the near-wall cavitation bubble and the air bubble has great significance for understanding the mechanism of air entrainment to alleviate cavitation in actual hydraulic engineering. To quantify the effect of the air bubble on the multi-cycle dynamics of the near-wall cavitation bubble, a more comprehensive compressible three-phase model considering the phase-change process was developed based on OpenFOAM, and corresponding validation was performed by comparing the simulated bubble shape with the published experimental values. The key features of the multi-cyclical evolution of the cavitation bubble are nicely reproduced based on the current numerical model. For the cavitation bubble near the solid wall containing a hemispherical air bubble, the simulated results reveal that the air bubble can reflect the shock wave and thus prevent it from impacting directly on the solid wall, which will help to uncover the microscopic mechanism of aeration avoiding cavitation damage. The dynamical features of the cavitation bubble at different dimensionless distances (γ1) and dimensionless sizes (ε) are investigated and analyzed. For the near-wall cavitation bubble with an air-entrapping hole, the air hole plays a crucial role in the multi-cycle dynamics of the cavitation bubble, leading to the bubble that is always far away from both the air hole and the solid wall. Thus, the current results may provide a potential application for preventing the wall damage caused by the impact of the liquid jet.