bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracking interface position of a high-speed imploding composite liner based on magnetic diffusion difference
Authors: Zhou Zhongyu , Gu Zhuowei , Tan Fuli , Zhao Jianheng , Sun Chengwei
Published: July 2023

A technique for tracking the interface position of non-metal–metal composite liners during high-speed implosion is proposed in this paper. Based on the magnetic diffusion difference between metal and non-metal, the interface position information is obtained by measuring magnetic fields in the cavity of the liner. An efficient magnetic flux estimation algorithm based on iterative magnetic diffusion simulation is also proposed to estimate the magnetic flux loss of the liner. Numerical experiments show that the estimation algorithm can reduce the relative error to less than 0.5%. The composite solid liner experimental results show that the maximum error is about 2% under imperfect experimental conditions. Detailed analysis suggests that this method can be widely applied to non-metallic sample materials (electrical conductivity is less than 103 ∼ 104 S/m). The technique provides a useful supplement to the existing interface diagnosis methods for high-speed implosion liners.
TAMM: Tensor algebra for many-body methods
Authors: Mutlu Erdal , Panyala Ajay , Gawande Nitin , Bagusetty Abhishek , Glabe Jeffrey , Kim Jinsung , Kowalski Karol , Bauman Nicholas P. , Peng Bo , Pathak Himadri , Brabec Jiri , Krishnamoorthy Sriram
Published: July 2023

Tensor algebra operations such as contractions in computational chemistry consume a significant fraction of the computing time on large-scale computing platforms. The widespread use of tensor contractions between large multi-dimensional tensors in describing electronic structure theory has motivated the development of multiple tensor algebra frameworks targeting heterogeneous computing platforms. In this paper, we present Tensor Algebra for Many-body Methods (TAMM), a framework for productive and performance-portable development of scalable computational chemistry methods. TAMM decouples the specification of the computation from the execution of these operations on available high-performance computing systems. With this design choice, the scientific application developers (domain scientists) can focus on the algorithmic requirements using the tensor algebra interface provided by TAMM, whereas high-performance computing developers can direct their attention to various optimizations on the underlying constructs, such as efficient data distribution, optimized scheduling algorithms, and efficient use of intra-node resources (e.g., graphics processing units). The modular structure of TAMM allows it to support different hardware architectures and incorporate new algorithmic advances. We describe the TAMM framework and our approach to the sustainable development of scalable ground- and excited-state electronic structure methods. We present case studies highlighting the ease of use, including the performance and productivity gains compared to other frameworks.
Composite Patankar-Euler methods for positive simulations of stochastic differential equation models for biological regulatory systems
Authors: Chen Aimin , Zhou Tianshou , Burrage Pamela , Tian Tianhai , Burrage Kevin
Published: July 2023

Stochastic differential equations (SDE) are a powerful tool to model biological regulatory processes with intrinsic and extrinsic noise. However, numerical simulations of SDE models may be problematic if the values of noise terms are negative and large, which is not realistic for biological systems since the molecular copy numbers or protein concentrations should be non-negative. To address this issue, we propose the composite Patankar-Euler methods to obtain positive simulations of SDE models. A SDE model is separated into three parts, namely, the positive-valued drift terms, negative-valued drift terms, and diffusion terms. We first propose the deterministic Patankar-Euler method to avoid negative solutions generated from the negative-valued drift terms. The stochastic Patankar-Euler method is designed to avoid negative solutions generated from both the negative-valued drift terms and diffusion terms. These Patankar-Euler methods have the strong convergence order of a half. The composite Patankar-Euler methods are the combinations of the explicit Euler method, deterministic Patankar-Euler method, and stochastic Patankar-Euler method. Three SDE system models are used to examine the effectiveness, accuracy, and convergence properties of the composite Patankar-Euler methods. Numerical results suggest that the composite Patankar-Euler methods are effective methods to ensure positive simulations when any appropriate stepsize is used.
Energy-based clustering: Fast and robust clustering of data with known likelihood functions
Authors: Thürlemann Moritz , Riniker Sereina
Published: July 2023

Clustering has become an indispensable tool in the presence of increasingly large and complex datasets. Most clustering algorithms depend, either explicitly or implicitly, on the sampled density. However, estimated densities are fragile due to the curse of dimensionality and finite sampling effects, for instance, in molecular dynamics simulations. To avoid the dependence on estimated densities, an energy-based clustering (EBC) algorithm based on the Metropolis acceptance criterion is developed in this work. In the proposed formulation, EBC can be considered a generalization of spectral clustering in the limit of large temperatures. Taking the potential energy of a sample explicitly into account alleviates requirements regarding the distribution of the data. In addition, it permits the subsampling of densely sampled regions, which can result in significant speed-ups and sublinear scaling. The algorithm is validated on a range of test systems including molecular dynamics trajectories of alanine dipeptide and the Trp-cage miniprotein. Our results show that including information about the potential-energy surface can largely decouple clustering from the sampled density.
Enhanced DC-biased energy-storage performance in lead-free relaxor ferroelectric ceramics for high-density power converters
Authors: Zhao Lihua , Lan Guitian , Jia Shenli , Wu Longwen
Published: July 2023

Dielectric energy-storage capacitors are among the main enabling technologies in high-density power converters, in which lead-free relaxor ferroelectric ceramics have been paid particular attention to. However, low energy-storage performance at elevated temperature and high electric field, and the lack of application-oriented evaluation are among the primary blocks stumbling their progress. As a demonstration, 0.87BaTiO3-0.13Bi[Zn2/3(Nb0.85Ta0.15)1/3]O3 (BTBZNT) lead-free relaxor ferroelectric ceramics were modified by linear dielectric CaZrO3 (CZ) with various contents of 0, 0.1, 0.2, and 0.3 (CZ0, CZ1, CZ2, and CZ3). XRD and Raman results reveal major perovskite phases, and densely sintered ceramics were witnessed from the SEM images. Unchanged weakly coupled relaxor behavior was confirmed by the big critical coefficient of 1.6–1.8 from the modified Curie–Weiss law and the large activation energy of 0.29–0.32 eV from the Volgel–Fulcher fittings, and CZ was found to suppress high-temperature loss. From the normal polarization–electric field (P–E) loops, CZ0 is optimal for energy-storage owing to the highest discharged energy density and modest efficiency. Nevertheless, from the application-oriented DC-biased P–E loops, CZ1 is oppositely superior to CZ0 because of the higher permittivity and lower loss leading to higher discharged energy density and efficiency at DC-biased electric field. Moreover, CZ1 outperforms CZ0 in the higher capacitance density and lower temperature rise at higher temperature and electric field. Enhanced DC-biased energy-storage performance in BTBZNT ceramics modified by CZ was achieved, which should enlighten the advance of energy-storage ceramics targeting the application in high-density power converters.
Polishing and etching damages of ZnO single crystals studied using time-resolved photoluminescence spectroscopy
Authors: Kasuya T. , Shima K. , Chichibu S. F.
Published: July 2023

Controlled thinning of wide bandgap semiconductors by chemo-mechanical polishing (CMP) and/or reactive ion etching (RIE) has been one of the versatile methods for various optoelectronic applications. The influences of CMP and subsequent wet chemical etching, as well as independent RIE, on the room-temperature photoluminescence lifetime for the near-band-edge emission [τPLNBE(RT)] of O-polarity c-plane ZnO single crystals were examined by using time-resolved photoluminescence measurements. τPLNBE(RT) decreased from a nanosecond range to a few picoseconds (ps) by a conventional CMP, indicating a generation of high-concentration midgap recombination centers, such as nonradiative recombination centers and deep radiative recombination centers. τPLNBE(RT) was progressively regained up to 600 ps by a subsequent etching using HCl aqueous solution. However, the recovery saturated at the etching depth of about 200 nm and τPLNBE(RT) was not restored even after etching by 350 nm. The results indicate the introduction of certain structural deformations during the CMP. Because x-ray diffraction measurement revealed the presence of incoherent surface domains right after the CMP and the HCl etching gave rise to inhomogeneously etched canyons, nonradiative recombination centers, such as dislocations and vacancy clusters, are likely generated by mechanical shear stresses. τPLNBE(RT) also decreased by the RIE. However, the degradation was less significant than the case for the CMP, because RIE scarcely gives mechanical stresses. Interestingly, τPLNBE(RT) for the samples etched under higher plasma power was longer than the lower power cases. From the results of x-ray photoelectron spectroscopy measurements, unintentionally deposited oxide films containing Si are proposed to act as an attenuating layer for the introduction of nonradiative recombination centers.
The bandgap characteristics of a flexural beam with periodic arrays of inertial amplification cantilever-type resonators
Authors: Sun Yonghang , Xi Chenyang , Dong Jingjie , Zheng Hui , Lee Heow Pueh
Published: July 2023

This paper presents the investigation of a metastructure, built with periodic arrays of inertial amplification (IA) cantilever-type resonators on a host beam, to improve its low-frequency flexural wave attenuation performance. The IA mechanism is composed of an additional mass and three rigid bars, which are connected by hinges and embedded on the host beam and cantilever-type resonators, respectively. The dynamical model of an IA cantilever-type resonant beam (IACRB) is established by the spectral element method, and its bandgap characteristics and vibration transmissibility are verified numerically and experimentally. The bandgaps of the lumped mass cantilever-type resonant beam are compared to those of the IACRB, showing that the latter has better low-frequency wave attenuation ability. To reveal the underlying physics, the effects of the amplification ratio, IA span, and length ratio of cantilever-type resonators on the band diagram of the IACRB are investigated. It is found that the variation of the amplification ratio results in the bandgap near-coupling phenomenon and the bandgap transposition phenomenon. The increase of IA span by changing position 1 weakens the coupling effect of local resonance and IA. However, the increase of IA span by changing position 2 creates the super-wide pseudo-bandgap as well, which is potential in engineering practices. The variation of the length ratio of cantilever-type resonators decreases its first bending modal frequency and shifts the IA bandgap to a lower frequency range slightly. The modal analysis results of the IACRB show that the proposed mechanism affects the modal distributions of the host structure. The modal frequencies existing in bandgaps are caused by the local vibration mode of the ends of the IACRB.
Experimental and numerical investigations on the effect of a novel internal surface micro-grooving toward improving convective heat transfer performance of tube heat exchangers
Authors: Eid M. M. A. A. , Zubir M. N. M. , Muhamad M. R. , Kazi S. N. , Aznam S. Mt , Rony M. H. , Ibrahim F. A. , Alam Md. Shadab , Sadri Rad
Published: July 2023

In the present work, the use of passive heat transfer enhancement technique through surface alteration was explored. The enhancement was achieved through internal conduit surface micro-grooving using a new apparatus that was developed by modifying a magnetic abrasive finishing technique. A new surface profile was created and later verified using optical and laser profiler measurements. The new profile was numerically investigated to compare the heat transfer and hydrodynamic performance against other profiles that have been studied in the literature. It was found from the results that the new profile shows much higher heat transfer improvement and comparable pressure loss to the previously investigated profiles (i.e., square, rectangular, trapezoidal, and circular). Overall, the new groove geometry provides the highest performance followed by the circular, triangular, curvy, square, and rectangular grooves. Also, the results indicate that designs with a smooth profile performs better than those with sharp edges, owing to the elimination of stationary fluid spots within the grooves. The effectiveness between the profiles was compared based on the level of heat transfer enhancement against the flow penalty. Experimental validation was further conducted for the experimentally generated groove. The results revealed that a relatively small surface temperature drop was obtained, corresponding to a slight improvement in heat transfer. This confirms the results generated by the simulation that groove size plays a major role in attaining significant improvement in heat transfer.
Quantum sensing of local stray field environment of micron-scale magnetic disks
Authors: Zhou Jingcheng , Yan Gerald Q. , Huang Mengqi , McLaughlin Nathan J. , Du Chunhui Rita , Wang Hailong
Published: July 2023

Local characterization of the properties and performances of miniaturized magnetic devices is a prerequisite for advancing present on-chip spintronic technologies. Utilizing nitrogen-vacancy (NV) centers in diamond, here we report quantum sensing of spin wave modes and magnetic stray field environment of patterned micrometer-scale Y3Fe5O12 (YIG) disks at the submicrometer length scale. Taking advantage of wide-field magnetometry techniques using NV ensembles, we map the spatially dependent NV electron spin resonances and Rabi oscillations in response to local variations of the stray fields emanating from a proximal YIG pattern. Our experimental data are in excellent agreement with theoretical predictions and micromagnetic simulation results, highlighting the significant opportunities offered by NV centers for probing the local magnetic properties of functional solid-state devices. The presented quantum sensing strategy may also find applications in the development of next-generation spintronic circuits with improved scalability and density.
De-wetting of evaporating drops on regular patterns of triangular posts
Authors: Peng Hsuan-Yi , Liu Bang-Yan , Lo Chi-Chun , Chen Li-Jen , Seemann Ralf , Brinkmann Martin
Published: July 2023

Directional wicking and spreading of liquids can be achieved by regular micro-patterns of specifically designed topographic features that break the reflection symmetry of the underlying pattern. The present study aims to understand the formation and stability of wetting films during the evaporation of volatile liquid drops on surfaces with a micro-pattern of triangular posts arranged in a rectangular lattice. Depending on the density and aspect ratio of the posts, we observe either spherical-cap shaped drops with a mobile three-phase contact line or the formation of circular or angular drops with a pinned three-phase contact line. Drops of the latter class eventually evolve into a liquid film extending to the initial footprint of the drop and a shrinking cap-shaped drop sitting on the film. The drop evolution is controlled by the density and aspect ratio of the posts, while no influence of the orientation of the triangular posts on the contact line mobility becomes evident. Our experiments corroborate previous results of systematic numerical energy minimization, predicting that conditions for a spontaneous retraction of a wicking liquid film depend weakly on the orientation of the film edge relative to the micro-pattern.
Magnetism-dependent martensitic phase transition in Ni2Mn-based all-d-metal Heusler compounds
Authors: Li Guijiang , Xu Lei , Ding Zhiwen , Cao Zhenhua
Published: July 2023

In this study, the all-d-metal Heusler compounds Ni2MnT (T = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, and W) were considered as representative examples, and the magnetism-dependent martensitic phase transition was systematically investigated by first-principles calculations. Comparative analysis of the calculated magnetic states-dependent elastic parameters, electronic structures, and thermodynamic parameters indicates that weakly magnetic Ni2MnT compounds with late transition metal atoms show higher possibilities of martensitic phase transition. Although magnetism is not the necessary condition for martensitic phase transition, the strong magnetic moment in Ni2MnT compounds with early transition metal atoms can suppress the occurrence of martensitic phase transition. When the magnetism is absent or becomes weak, the suppressed martensitic phase transition can be re-evoked. The current study indicates that magnetism plays an important role in determining the martensitic phase transition in all-d-metal Heusler compounds Ni2MnT. Careful control of the magnetism can serve as another parameter to tune martensitic phase transition in Ni−Mn-based all-d-metal Heusler compounds. This study can be helpful to explore and design outstanding candidate materials for solid-state refrigeration applications based on the martensitic phase transition.
Wavelet-based pressure decomposition for airfoil noise in low-Mach number flows
Authors: Kang Donghun , Lee Seongkyu , Brouzet Davy , Lele Sanjiva K.
Published: July 2023

The paper applies a wavelet filtering method based on the recursive denoising algorithm to airfoil noise in low-Mach number flows. The pressure field around the airfoil is decomposed into coherent contributions corresponding to denoised pressure and incoherent pressure corresponding to background noise. The pressure data are obtained from Large-Eddy Simulations. Both the flow and acoustic solvers are validated against experimental data at a zero angle of attack, Reynolds numbers, Re=3.2×105 and 4×105, and Mach numbers, M=0.093 and 0.058, respectively. The convergence trend and statistical nature of the wavelet algorithm are analyzed. Additionally, the decomposed pressures are examined by comparing the wavelet-based decomposition with the traditional wavenumber–frequency decomposition, and spectral analyses are conducted on the decomposed pressures. The results show that the denoised pressure represents physical phenomena associated with hydrodynamic wavy structures moving along the wall and sound propagation generated near the tripping region and the trailing edge. On the other hand, the incoherent pressure or background noise exhibits a small and constant amplitude closely adhering to the Gaussian distribution. Dynamic mode decomposition modes reveal that this background noise is prominent around the tripping and trailing-edge regions where flow perturbations are significant, but it either barely propagates to the far field or dissipates quickly. The far-field acoustic spectrum is predominantly influenced by the physical or denoised component. However, a cautious interpretation is necessary in the high-frequency range, where background noise still contributes to the far-field noise. The paper explores the potential applications of the wavelet algorithm in identifying and removing background noise.
Gaussian process regression adaptive density-guided approach: Toward calculations of potential energy surfaces for larger molecules
Authors: Artiukhin Denis G. , Godtliebsen Ian H. , Schmitz Gunnar , Christiansen Ove
Published: July 2023

We present a new program implementation of the Gaussian process regression adaptive density-guided approach [Schmitz et al., J. Chem. Phys. 153, 064105 (2020)] for automatic and cost-efficient potential energy surface construction in the MidasCpp program. A number of technical and methodological improvements made allowed us to extend this approach toward calculations of larger molecular systems than those previously accessible and maintain the very high accuracy of constructed potential energy surfaces. On the methodological side, improvements were made by using a Δ-learning approach, predicting the difference against a fully harmonic potential, and employing a computationally more efficient hyperparameter optimization procedure. We demonstrate the performance of this method on a test set of molecules of growing size and show that up to 80% of single point calculations could be avoided, introducing a root mean square deviation in fundamental excitations of about 3 cm−1. A much higher accuracy with errors below 1 cm−1 could be achieved with tighter convergence thresholds still reducing the number of single point computations by up to 68%. We further support our findings with a detailed analysis of wall times measured while employing different electronic structure methods. Our results demonstrate that GPR-ADGA is an effective tool, which could be applied for cost-efficient calculations of potential energy surfaces suitable for highly accurate vibrational spectra simulations.
Electrical properties and parameter analysis of all-solid-state LaZrO/InO electric double-layer transistors
Authors: Nakazawa Hiromi , Ishii Hiroshi , Takamura Yuzuru
Published: July 2023

All-solid-state electric double-layer (EDL) thin-film transistors (TFTs) consisting of solution-processed LaZrO gate insulators and sputtered InO channels with thicknesses of 10–200 nm were prepared, and their microstructures and electrical properties were investigated. In addition, mobility, carrier concentration, and their gate-voltage dependence in the InO layer were analyzed during a transistor operation to clarify the electron transport properties. It was confirmed that LaZrO was amorphous and that InO crystallized and had an In2O3 bixbyite structure. The transfer conductance increased with the InO thickness, and its normalized value was maximized (3.6 mS/V) at an InO thickness of 200 nm. The maximum capacitance of LaZrO was 31 μF/cm2, strongly suggesting the formation of an EDL. Solid EDL-TFTs operated stably without deterioration at gate voltages up to 5 V, which usually degrade liquid-electrolyte EDL transistors via electrolysis. Assuming the formation of a 1-nm-thick EDL, the concentration of carrier electrons induced during the transistor operation was estimated to be 1019–1021 cm−3. Moreover, the mobility increased with the InO thickness and reached a maximum value of 68 cm2/(V s) at an InO thickness of 120 nm. The conduction electrons were significantly affected by grain boundary scattering and surface scattering, in addition to scattering within the crystal grain. An increase in the InO thickness, which improved the crystallinity in the crystal grain, reduced the barrier height and the effect of grain boundary scattering.
Effects of C–H stretching excitation on the dynamics of the O(1D) + CHD3 → OH/OD + CD3/CHD2 reaction
Authors: Lv Jing , Yang Jiayue , Zhang Dong , Blauert Florian , Jiang Bo , Dai Dongxu , Zhang Weiqing , Wu Guorong , Yang Wenshao , Shuai Quan , Yang Xueming
Published: July 2023

The vibrationally excited reaction O(1D) + CHD3(ν1 = 1) has been investigated by crossed-molecular-beam experiments with a time-sliced velocity map imaging technique. Detailed and quantitative information is extracted on the C–H stretching excitation effects on the reactivity and dynamics of the title reaction, with the help of preparation of C–H stretching excited CHD3 molecules by direct infrared excitation. Experimental results show that the vibrational stretching excitation of the C–H bond almost does not affect the relative contributions between different dynamical pathways for all product channels. For the OH + CD3 product channel, the vibrational energy of the C–H stretching excited CHD3 reagent is channeled exclusively into the vibrational energy of the OH products. The vibrational excitation of the CHD3 reactant changes the reactivities for the ground-state and umbrella-mode-excited CD3 channels very modestly, while it significantly suppresses the corresponding CHD2 channels. For the CHD2(ν1 = 1) channel, the stretching excited C–H bond of the CHD3 molecule acts almost as a pure spectator.
Coherent phonon relaxation in strontium titanate
Authors: Sylvester Jeremy , Choudhary Rashmi , Jalan Bharat , Ganikhanov Feruz
Published: July 2023

Ultrafast decays of the intrinsic phonon modes within 260–790 cm−1 range of frequencies, which are symmetry forbidden in the first-order Raman scattering in bulk SrTiO3 crystal, have been traced using time-resolved coherent Raman technique. The effective phonon decay times are within 0.86–1.38 ps and yield corresponding linewidths of 7.7–12.3 cm−1 for optical lattice vibrations. Symmetry breakage mechanisms related to free charged carriers resulting from vacancies do not appear to play a major role.
Engineering of niobium surfaces through accelerated neutral atom beam technology for quantum applications
Authors: Kar Soumen , Weiland Conan , Zhou Chenyu , Bhatia Ekta , Martinick Brian , Nalaskowski Jakub , Mucci John , Olson Stephen , Hung Pui Yee , Wells Ilyssa , Frost Hunter , Johnson Corbet S. , Murray Thomas , Kaushik Vidya , Kirkpatrick Sean , Chau Kiet , Walsh Michael J. , Liu Mingzhao , Papa Rao Satyavolu S.
Published: July 2023

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLSs). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by “surface engineering” (i.e., replacing the uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher intrinsic quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages accelerated neutral atom beam (ANAB) technology at 300 mm wafer scale. This ANAB is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 to 6 nm depending on ANAB process parameters. The modeling of variable-energy x-ray photoelectron spectroscopy data confirms the thickness and compositional control of Nb surface oxide by the ANAB process. These results correlate well with those from transmission electron microscopy and x-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times.
Improving the success rate of quantum algorithm attacking RSA encryption system
Authors: Dong Yumin , Liu Hengrui , Fu Yanying , Che Xuanxuan
Published: July 2023

Shor’s factorization algorithm (SFA) aims at finding the non-trivial factor of a given composite number, but the algorithm does not always work. In some cases, it has to call back to the beginning of the algorithm to make recalculation. After the analysis of the principle of SFA and the characteristics of RSA public-key cryptography with a series of data calculations, it can be concluded that the random value selected by the algorithm is closely related to whether the obtained period is effective. Therefore, a new optimized scheme is proposed to tackle with this defect from two perspectives: (a) When the a value is a perfect square, the algorithm can be completed with an odd cycle r. (b) When the period r obtained by the randomly selected a value is a multiple of 3, the algorithm can be completed by modifying the decomposition method to relax the requirements for the period without affecting the complexity of the algorithm. Due to the limitations of hardware in applying the quantum algorithms, the classical algorithm is applied to simulate quantum algorithms to test the success rate of decomposition of some composite numbers. The result indicates the effectiveness of the improved algorithm, which significantly reduces the probability of repeated operations to save the quantum circuit resources.
A data-driven approach to model enstrophy transfers in large eddy simulation of forced two-dimensional turbulence
Authors: Ayapilla Aditya Sai Pranith
Published: July 2023

Contemporary research on the application of data-driven techniques to modeling subgrid closure in two-dimensional turbulence has been limited. Furthermore, the incorporation of the enstrophy cascade and other two-dimensional turbulence-specific physics has received insufficient attention. To address these gaps, a novel physics-based shallow feed-forward neural network framework was designed in this study to model subgrid closure in three selected cases of forced two-dimensional turbulence with a forcing that provides energy and enstrophy at a particular wavenumber. As a novel approach, we trained our framework to learn the subgrid vorticity transport vector from a set of appropriate resolved flow variables. Another framework used in recent works which directly learned the subgrid forcing field was also investigated. Both frameworks were assessed using a priori and a posteriori tests for two selected filter widths. Both frameworks performed accurately for the lower filter width but less accurately for the higher filter width. However, we demonstrate that our new framework has wider usefulness for model diagnosis. Ad hoc clipping procedures were used to make the models more generalizable to higher filter widths, and stable and consistent a posteriori tests were observed for all test cases and filter widths when the subgrid forcing field was modified to enhance the model's subgrid dissipative characteristics. In contrast, modifying the enstrophy fluxes did not perform as consistently. These findings demonstrate the potential of the novel physics-based framework for improving subgrid modeling in two-dimensional turbulence.
Numerical design of surface magneto-plasmon sensors of Au/Co double-layer square arrayed nanopores on the continuous gold thin film
Authors: Zhang Chang , Cui Xiaojian , Zhang Weiwei , Zhu Ruixue , Song Yujun
Published: July 2023

Surface magneto-plasmon (SMP) sensors have attracted continuous attention due to their field enhanced signal-to-noise ratios, sensitivities, and detection limits. Although many progresses have been achieved in the nanodots, nanorods, or nanodiscs, few studies have been conducted on films containing arrays of nanopores or nanoholes. SMP sensors based on arrays of nanopores could be much more promising for future ultrasensitive optical detectors since they can couple the SMP enhancement with Fabry–Pérot interference of nanopores for high-performance resonator sensors that can be further tuned under a magnetic field. We, thus, propose a high-performance SMP sensor based on the magneto-optical Kerr effect (MOKE) of films containing a square array of Au–Co double-layer nanopores on the Au film substrate or SMP-MOKE sensor. The local electric field around the magneto-plasmon arrays of nanopore photonic crystals can be greatly enhanced by applying an external magnetic field due to their magneto-optical activity and excitation of high-quality surface plasmon resonances. Multi-physics coupling simulations and validation by COMSOL on the structure-dependent optical properties suggest that the proposed SMP-MOKE sensor has a high sensitivity of 711 nm/Refractive Index Units (RIUs) and a figure of merit (FOM) of the order of 105 RIU−1, which is an order of magnitude greater than the best grating-type sensors, to the best of our knowledge. Our results shall facilitate the theoretical design for the future fabrication of ultra-sensitive sensors or resonators with excellent FOM and reliability for air-quality monitoring or chemical sensing, etc.
Electronic coarse-graining of long conjugated molecules: Case study of non-fullerene acceptors
Authors: Zhugayevych Andriy , Lin Kun-Han , Andrienko Denis
Published: July 2023

By considering only one electronic state per molecule, charge transport models of molecular solids neglect intramolecular charge transfer. This approximation excludes materials with quasi-degenerate spatially separated frontier orbitals, such as non-fullerene acceptors (NFAs) and symmetric thermally activated delayed fluorescence emitters. By analyzing the electronic structure of room-temperature molecular conformers of a prototypical NFA, ITIC-4F, we conclude that the electron is localized on one of the two acceptor blocks with the mean intramolecular transfer integral of 120 meV, which is comparable with intermolecular couplings. Therefore, the minimal basis for acceptor–donor–acceptor (A–D–A) molecules consists of two molecular orbitals localized on the acceptor blocks. This basis is robust even with respect to geometry distortions in an amorphous solid, in contrast to the basis of two lowest unoccupied canonical molecular orbitals withstanding only thermal fluctuations in a crystal. The charge carrier mobility can be underestimated by a factor of two when using single site approximation for A–D–A molecules in their typical crystalline packings.
Dispersive response of polar optical phonon modes on the dielectric and size effects in a nitride nanostructure
Authors: Zhang Li , Wang Qi , Wang Guang-Hui
Published: July 2023

Within the framework of the macroscopic dielectric continuum model, the dispersive spectra of polar optical phonon modes of III-nitride based nanostructures with different inner and outer dielectric media are investigated in this paper. The dielectric and quantum size effects on the dispersive frequencies of phonon modes are focused and emphasized. In the case of GaN quantum rings (QRs), we found that the dielectric constant of the inner/outer medium could significantly influence the dispersive spectra of the surface optical (SO) phonon mode as the high/low-frequency SO phonon modes are mainly localized at the inner/outer surface of QRs, respectively. Moreover, such effects associated with different crystallographic structures of GaN, i.e., the wurtzite (WZ) and zinc blende (ZB) crystal structures, are also studied in detail, showing the different degenerating behavior and electron–phonon coupling strength. The results obtained in this study provide a beneficial opportunity to independently adjust dispersive spectra of the two branches of SO modes in GaN nanostructures; thus, it could be used to design and develop phonon-based detectors and sensors.
Dissecting the ingredients of optimally tuned range-separated hybrid models for reliable description of non-adiabatic couplings
Authors: Izadkhast Tahereh , Alipour Mojtaba
Published: July 2023

Perusing the non-radiative processes requires a reliable prediction of non-adiabatic couplings (NACs) describing the interaction of two Born–Oppenheimer surfaces. In this regard, the development of appropriate and affordable theoretical methods that accurately account for the NAC terms between different excited-states is desirable. In this work, we develop and validate several variants of the optimally tuned range-separated hybrid functionals (OT-RSHs) for investigating NACs and related properties, such as excited states energy gaps and NAC forces, within the time-dependent density functional theory framework. Particular attention is paid to the influence of the underlying density functional approximations (DFAs), the short- and long-range Hartree–Fock (HF) exchange contributions, and the range-separation parameter. Considering several radical cations and sodium-doped ammonia clusters with the available reference data for the NACs and related quantities as the working models, we have evaluated the applicability and accountability of the proposed OT-RSHs. The obtained results unveil that any combination of the ingredients in the proposed models is not proper for describing the NACs, but a particular compromise among the involved parameters is needed to achieve reliable accuracy. Scrutinizing the results of our developed methods, the OT-RSHs based on the PBEPW91, BPW91, and PBE exchange and correlation DFAs, including about 30% HF exchange at the short-range regime, appeared to be the best performers. We also find that the newly developed OT-RSHs with correct asymptotic exchange-correlation potential have superior performances as compared to their standard counterparts with the default parameters and many earlier hybrids with both fixed and interelectronic distance-dependent HF exchange. The recommended OT-RSHs in this study can hopefully be applicable as computationally efficient alternatives to the expensive wave function-based methods for the systems prone to non-adiabatic properties as well as to screen out the novel candidates prior to their challenging synthesis.
Flexible planar Hall effect sensor with sub-200 pT resolution
Authors: Nhalil Hariharan , Lahav Daniel , Schultz Moty , Amrusi Shai , Grosz Asaf , Klein Lior
Published: July 2023

Flexible sensors are important for applications, such as wearable medical devices, soft robotics, and more, as they can easily conform to soft and irregularly shaped surfaces. This study presents elliptical planar Hall effect magnetic sensors fabricated on a polyamide tape with an equivalent magnetic noise (EMN) better than 200 pT/Hz. The sensor is characterized in flat and bent states with a bent radius of 10 mm. An EMN of 200 and 400 pT/Hz in flat and bent states, respectively, is achieved at a frequency of 100 Hz. The remarkable EMN combined with a simple, low-cost fabrication process makes these sensors a promising candidate for flexible electronics.
Modeling the aqueous interface of amorphous TiO2 using deep potential molecular dynamics
Authors: Ding Zhutian , Selloni Annabella
Published: July 2023

Amorphous titanium dioxide (a-TiO2) is widely used as a coating material in applications such as electrochemistry and self-cleaning surfaces where its interface with water has a central role. However, little is known about the structures of the a-TiO2 surface and aqueous interface, particularly at the microscopic level. In this work, we construct a model of the a-TiO2 surface via a cut-melt-and-quench procedure based on molecular dynamics simulations with deep neural network potentials (DPs) trained on density functional theory data. After interfacing the a-TiO2 surface with water, we investigate the structure and dynamics of the resulting system using a combination of DP-based molecular dynamics (DPMD) and ab initio molecular dynamics (AIMD) simulations. Both AIMD and DPMD simulations reveal that the distribution of water on the a-TiO2 surface lacks distinct layers normally found at the aqueous interface of crystalline TiO2, leading to an ∼10 times faster diffusion of water at the interface. Bridging hydroxyls (Ti2–ObH) resulting from water dissociation decay several times more slowly than terminal hydroxyls (Ti–OwH) due to fast Ti–OwH2 → Ti–OwH proton exchange events. These results provide a basis for a detailed understanding of the properties of a-TiO2 in electrochemical environments. Moreover, the procedure of generating the a-TiO2-interface employed here is generally applicable to studying the aqueous interfaces of amorphous metal oxides.
High mobility GaN drift layer on Si substrates: The role of surface N vacancy on carbon incorporation
Authors: Chen Zhenghao , Yang Xuelin , Liu Danshuo , Cai Zidong , Huang Huayang , Sang Liwen , Xu Fujun , Wang Xinqiang , Ge Weikun , Shen Bo
Published: July 2023

The control of carbon (C) impurity plays a crucial role in achieving high mobility GaN drift layers for GaN vertical power devices. We investigate the effects of NH3 partial pressure on the C incorporation in GaN and find out that the NH3 partial pressure is the key parameter controlling the C concentration. It is found that the C concentration is inversely proportional to the square of NH3 partial pressure under a fixed growth rate. Further physical analysis indicates that higher NH3 partial pressure results in a lower surface N vacancy (VN) concentration and, thus, the lower C incorporation efficiency. Under such a guidance, the C concentration in GaN can be reduced to as low as ∼1.7 × 1015/cm3 at a growth rate of 1 μm/h. As a consequence, a record high electron mobility of 1227 cm2/V·s at the room temperature is achieved for a GaN drift layer grown on Si substrates. Our strategy is effective in C control and paves the way for realizing high performance kV-class GaN vertical power devices on Si substrates.
Further thoughts on buoyancy-induced instability of a variable viscosity fluid saturating a porous slab
Authors: Shankar B. M. , Nagamani K. V. , Shivakumara I. S.
Published: July 2023

The stability of buoyant flow in a vertical porous layer bounded by impermeable-isothermal boundaries is studied insofar as the variability of fluid viscosity with temperature is concerned. The flow is governed by modified Darcy's law with two different forms of viscosity–temperature relationships namely, quadratic and exponential. The modal analysis is carried out with a velocity–temperature formulation of the governing equations for the perturbations. The temperature-dependence of the viscosity forbids the energy analysis of Gill [“A proof that convection in a porous vertical slab is stable,” J. Fluid Mech. 35, 545–547 (1969)] in embarking upon any definite conclusion on the stability of fluid flow even under the limit of an infinite Prandtl–Darcy number, and consequently, the stability eigenvalue problem is solved numerically. Types of temperature-dependent viscosity laws are found to demonstrate conflicting behavior on the stability characteristics of the base flow. The results show that the base flow is linearly stable if the viscosity varies with temperature quadratically. On the contrary, instability emerges for an exponential type of variation in viscosity beyond a certain range of values of the corresponding viscosity parameter depending on the Prandtl–Darcy number. It is established that an increase in the value of the viscosity parameter is to decrease the critical Darcy–Rayleigh number markedly and thereby destabilizes the fluid flow.
Insights on transport performance, thermodynamic properties, and mechanical properties of Ruddlesden–Popper antiperovskite LiBr(Li2OHBr)2 and LiBr(Li3OBr)2
Authors: Li Congcong , Lian Sen , Kang Chen , Ren Junfeng , Chen Meina
Published: July 2023

Due to high ion conductivity, low cost, and adjustable composition, antiperovskite has attracted much attention as a potentially useful material in solid-state batteries. Compared with simple antiperovskite, Ruddlesden–Popper (R–P) antiperovskite is an updated material, which is not only more stable but also reported to significantly enhance conductivity when added to simple antiperovskite. However, systematic theoretical research on R–P antiperovskite is scarce, hindering its further development. In this study, the recently reported easily synthesized R–P antiperovskite LiBr(Li2OHBr)2 is calculated for the first time. Comparative calculations were conducted on the transport performance, thermodynamic properties, and mechanical properties of H-rich LiBr(Li2OHBr)2 and H-free LiBr(Li3OBr)2. Our results indicate that due to the presence of protons, LiBr(Li2OHBr)2 is more prone to defects, and synthesizing more LiBr Schottky defects can improve its Li-ion conductivity. Young’s modulus of the LiBr(Li2OHBr)2 is as low as 30.61 GPa, which is beneficial for its application as a sintering aid. However, the calculated Pugh’s ratio (B/G) of 1.28 and 1.50, respectively, indicates that R–P antiperovskites LiBr(Li2OHBr)2 and LiBr(Li3OBr)2 exhibit mechanical brittleness, which is not conducive to its application as solid electrolytes. Through quasi-harmonic approximation, we found that the linear thermal expansion coefficient of LiBr(Li2OHBr)2 is 2.07 × 10−5 K−1, which is more advantageous in matching electrodes than LiBr(Li3OBr)2 and even simple antiperovskites. Overall, our research provides comprehensive insights into the practical application of R–P antiperovskite in solid-state batteries.
Statistical mechanics of the GENERIC framework under external forcing
Authors: Español Pep
Published: July 2023

The General Equation for Non-Equilibrium Reversible Irreversible Coupling (generic) framework provides a thermodynamically consistent approach to describe the evolution of coarse-grained variables. This framework states that Markovian dynamic equations governing the evolution of coarse-grained variables have a universal structure that ensures energy conservation (first law) and entropy increase (second law). However, the presence of external time-dependent forces can break the energy conservation law, requiring modifications to the framework’s structure. To address this issue, we start from a rigorous and exact transport equation for the average of a set of coarse-grained variables derived from a projection operator technique in the presence of external forces. Under the Markovian approximation, this approach provides the statistical mechanics underpinning of the generic framework under external forcing conditions. By doing so, we can account for the effects of external forcing on the system’s evolution while ensuring thermodynamic consistency.
Carcass traits and meat lipid profile of cull cows fed palm kernel cake
Authors: Soares Camila , Santos Laize V. , Silva Fabiano F. , Barroso Daniele S. , Rocha Wéder J. B. , Santos Marceliana C. , Silva João W. D. , Paixão Tarcísio R. , Silva Ana P. G. , Carvalho Gleidson G. P. , Lima Júnior Dorgival M. , Silva Robério R.
Published: July 2023

Context Among the by-products derived from oilseeds, palm kernel cake (PKC) contains high concentrations of protein, fat, and fibre, which allows some flexibility in the use of this ingredient in ruminant diets. Aim This study examined the effects of including palm kernel cake (PKC) in high-grain diets for cull cows on production performance, carcass traits, and meat fatty acid profile. Methods Thirty-six ½ Girolando cows at 83 ± 5 months of age, with an average liveweight of 384.88 kg ± 59.18, were confined in collective stalls for 90 days. The animals were distributed into the following four diet groups: 0% (control), 8%, 16%, or 24% inclusion of PKC in the diet dry matter (DM). Key results On the basis of regression analysis, the highest slaughter weight and carcass weight were at PKC inclusion levels of 11.5% and 10.3% respectively. Backfat thickness was greatest (8.8 mm, P < 0.01) in the carcasses of cows fed the diet with 15.1% PKC (on the basis of regression analysis), whereas the total lipid content in the meat decreased linearly (P < 0.05) with PKC inclusion. The C10:0, C12:0, C14:0, C14:1, C16:0, C16:1, C17:1, C18:0, C18:2n6t, and C20:5n3 fatty acids in the longissimus thoracis muscle responded quadratically (P < 0.05) to the inclusion of PKC. The highest concentration of desirable fatty acids was obtained with the inclusion of 11% PKC in the diet (on the basis of regression analysis). There was a linear increase in C14:1, C20:2, and C22:2 fatty acids and Δ9 desaturase 14 and 16 activity indices in the muscle of cows fed PKC. Conclusion We recommend the inclusion of 10% PKC in the diet of cull cows fed high-grain diets. Intramuscular fatty-acid proportions were appreciably different from those reported for young B. taurus steers and heifers finished on high-concentrate diets. Implications Therefore, inclusion of PKC is an excellent alternative to reduce production costs, having the availability and quality of the product as a limiting factor, since PKC is an industrial by-product.