bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and Implementation of an Aural Rehabilitation Program Using Community Health Workers in Rural Alabama
Authors: Hay-McCutcheon Marcia J. , Hubbard Abigail , Brothers Emma B. , Straub Kerstin , Allen Rebecca S. , Hardy Claudia , Tye-Murray Nancy
Published: August 2024

Purpose:

Considering the lack of audiological care in many areas across the United States, it is crucial to develop new models of hearing health care. Described within this document is a procedure used to develop and implement an aural rehabilitation (AR) program and a community health worker (CHW) educational training program in West Central and South Alabama. The AR program and the CHW educational training program were used to assist those with hearing loss in rural Alabama communities who received over-the-counter hearing aids (OTC HAs). The work described was part of a registered clinical trial (NCT04671381) with OTC HAs in rural Alabama communities.

Method:

The development and implementation of the AR program and CHW training program was conducted using foundational work from experiential learning principals and from experts in AR and community outreach and engagement.

Results:

Over the course of 3 years from March 2021 to March 2024, the AR program and CHW training were developed and implemented. Guidance from the study personnel, consultants, and CHWs helped to refine the AR program and CHW training after implementation.

Conclusion:

Future studies will assess the success of the AR program through quantifying outcomes from speech perception testing and survey completion obtained from adults in rural communities who enroll in the OTC HA clinical trial.
Low‐carbon optimal scheduling strategy for multi‐agent integrated energy system of the park based on Stackelberg–Nash game
Authors: Chen Yanbo , Li Jiaqi , Fang Zhe , Zhang Ning , Huang Tao , Chen Zuomao
Published: August 2024

Under the background of achieving the dual‐carbon goal, the park is a natural experimental field for practicing the dual‐carbon goal. A low‐carbon optimal scheduling strategy for a multi‐agent park‐integrated energy system (P‐IES) based on the Stackelberg–Nash game is proposed. Firstly, a low‐carbon P‐IES scheduling model is established, considering the two‐stage operation of power‐to‐gas (P2G) technology and reward–punishment stepwise carbon trading mechanism. Then, a two‐layer game optimisation model is proposed with a park‐integrated energy system operator (P‐IESO) as the leader and multiple low‐carbon P‐IESs as followers. Among them, the parks are connected with each other through the power trading channels. Then, the Nash equilibrium solution is obtained by the iterative search method, and the uniqueness of the equilibrium solution of the game is proven, so as to determine the optimal pricing strategy of the operator. Finally, a typical industrial park is taken as an example for simulation verification. The example analysis verifies that the model can effectively reduce the system's carbon emissions and improve the park's economic benefits and low‐carbon levels, thereby achieving the coordinated development of low‐carbon and economic performance in the park.
Anti‐freezing electrolyte modification strategies toward low‐temperature aqueous zinc‐ion batteries
Authors: Yuan Xinyao , Zhang Di , Lu Hongfei , Duan Chenxu , Jin Yang
Published: August 2024

Due to the availability of zinc resources, and reduced security risks, aqueous zinc‐ion batteries (AZIBs) are potential contenders for next‐generation energy storage systems. With the multi‐scene application of AZIBs, the temperature adaptation of electrolytes poses a great challenge. However, the aqueous electrolyte is prone to freezing in sub‐zero environments, which leads to undesirable problems such as undesirable ion transfer and poor electrode/electrolyte interface, resulting in a sharp deterioration of the electrochemical properties of AZIBs in cold conditions and limited practical use of AZIBs. Antifreeze electrolyte modification strategies have gained popularity as effective ways to optimise the low‐temperature behaviour of AZIB. The results of recent studies of electrolyte modification strategies are systematically summarised for low‐temperature AZIBs, focusing on the modification methods, principles, and effects achieved. Firstly, the authors describe the mechanism of failure of AZIBs at low temperatures. Subsequently, the modification strategies of antifreeze electrolytes are summarised, including the utilisation of high salt content, the design of organic electrolytes, the adoption of antifreeze electrolyte additives, and the building of hydrogel electrolytes. Finally, the issues faced by electrolytes at low temperatures are further indicated and suggestions are provided for their future development.
Active reconfigurable intelligent surface‐aided multiple‐input‐multiple‐output radar detection in the presence of clutter
Authors: Zhang Yu , Li Da , Tang Bo , Zhang Haichuan , Zuo Lei
Published: August 2024

Reconfigurable intelligent surface (RIS) refers to a two‐dimensional smart surface consisting of massive number of reflecting elements. Both active RIS (ARIS) and passive RIS (PRIS) are promising technologies that can adapt and reconfigure the wireless environment, enhancing the reliability and capacity of wireless networks. The authors focus on enhancing the detection ability of ARIS/PRIS‐aided multiple‐input‐multiple‐output radar system in the presence of signal‐dependent clutter. Constant‐envelope constraint is imposed on the sought radar waveforms to improve the practicability of the radar system. To tackle the resultant non‐convex problem, a cyclic method based on minorisation–maximisation and alternating direction method of multipliers is derived to iteratively optimise the receive filters, the transmit waveforms, and the RIS coefficients. The major finding is that the distance between the radar and the ARIS has little to no impact on the radar signal‐to‐interference‐plus‐noise ratio (SINR). For the PRIS‐aided radar system, a simplified model can significantly improve the operational efficiency and has little impact on the radar SINR. Numerous results verify the effectiveness of the proposed algorithm.
Irradiation-driven mass transfer for massive companion stars in supersoft X-rays sources
Authors: Zhao Weitao , Meng Xiangcun , Cui Yingzhen
Published: August 2024

Context. Supersoft X-ray sources (SSSs) have been proposed as one of the progenitors for Type Ia supernovae. However, the exact origin of the quasi-periodic variability in the optical light curve remains a mystery.

Aims. In this work, our goal is to investigate the effect of the feedback of an evolved main-sequence companion star on X-ray irradiation and find whether periodic X-ray irradiation of the companion star could reproduce periodic mass transfer.

Methods. Using the Modules for Experiments in Stellar Astrophysics (MESA) code, we modeled the evolutionary track of the companion star under the influence of supersoft X-ray irradiation, and we calculated the resulting mass transfer rate.

Results. We find that the supersoft X-ray heating of the companion star can result in the expansion of the companion, causing it to greatly overflow its Roche lobe and thereby increasing the mass transfer rate. The periodic X-ray irradiation on the companion stars leads to periodic changes in the mass transfer rate. For a given companion star, higher irradiation efficiencies result in a higher mass transfer rate. Additionally, the mass transfer rate increases as the mass of the companion star decreases for a given irradiation efficiency.

Conclusions. The companion star undergoing thermal timescale mass transfer is periodically irradiated by the X-rays from the WD, which can lead to periodic enhancement of the mass transfer rate. The mechanism could be the origin of the quasi-periodic optical light curve in supersoft X-ray sources.
Discs are born eccentric
Authors: Commerçon Benoît , Lovascio Francesco , Lynch Elliot , Ragusa Enrico
Published: August 2024

Context. Recent observations have begun probing the early phases of disc formation, but little data yet exists on disc structure and morphology of Class 0 objects. Using simulations, we are able to lay out predictions of disc morphologies expected in future surveys of young discs. Based on detailed simulations of ab initio star formation by core collapse, we predict that early discs must be eccentric.

Aims. In this Letter, we study the morphology and, in particular, the eccentricity of discs formed in non-ideal magnetohydrodynamic (MHD) collapse simulations. We attempt to show that discs formed by cloud collapse are likely to be eccentric.

Methods. We ran non-ideal MHD collapse simulations in the adaptive mesh refinement code RAMSES with radiative transfer. We used state-of-the-art analysis methods to measure the disc eccentricity.

Results. We find that despite no asymmetry in the initial conditions, the discs formed are eccentric, with eccentricities on the order of 0.1.

Conclusions. These results may have important implications for protoplanetary disc dynamics and planet formation. The presence of eccentricity in young discs that is not seen at later stages of disc evolution is in tension with current viscous eccentricity damping models. This implies that there may be an as-yet undiscovered circularisation mechanism in circumstellar discs.
Clinical and morphological substantiation of the use of glycyrizzic acid in poultry farming
Authors: Gatiyatullin Ildar , Bazekin George , Dolinin Ilgiz
Published: August 2024

The paper presents a clinical and morphological justification for the use of glycyrrhizic acid in poultry farming. It was found that the use of glycyrrhizic acid in broiler chickens enhances the histological picture of the thymus with a pronounced image and differentiation of the cortical layer. Increased mitotic activity of thymocytes and improved blood supply to the organ were determined. Revealed, Fabricius’s bag of broiler chickens, which were given glycyrrhizic acid, has a fairly high level of functional dynamics. Installed, the thickness of the cortical layer of the thymus lobule in broiler chickens in the control group was 1.2 times lower than after the use of glycyrrhizic acid in broiler chickens in the experimental group, and the cerebral layer was 1.8 times less than in the experimental group. It was revealed that glycyrrhizic acid has a beneficial effect on the body of birds.
Efficacy of Recombinant Human Parathyroid Hormone 1–34 and Vitamin K2
Combination Therapy in Postmenopausal Osteoporosis
Authors: Zhang Zhuo , Xia Kun , Gong Wentao , Mai Ruopeng , Liu Peng , Lu Zhaogang
Published: August 2024

This study aimed to assess the efficacy and safety of a combined recombinant
human parathyroid hormone 1–34 [rhPTH (1–34)] and vitamin K2 therapy versus
vitamin K2 alone in the treatment of postmenopausal osteoporosis. A total of 77
postmenopausal osteoporosis patients were randomly divided into two groups.
Patients in one group received vitamin K2 alone, while patients in the other
group received a combination of rhPTH (1–34) and vitamin K2. Bone mineral
density (BMD), electrolyte levels, pain scores, bone metabolism levels, and
adverse drug reactions were compared pre- and post-treatment. Both two
treatments improved BMD, blood calcium concentrations, pain scores, and
increased osteocalcin and osteoprotegerin levels. Notably, the combined rhPTH
(1–34) and vitamin K2 treatment demonstrated superior efficacy in improving BMD
and bone metabolism markers. Furthermore, there was no significant difference in
the incidence of adverse reactions between the two groups, indicating the safety
of the combined treatment. In summary, the combined therapy of rhPTH (1–34) and
vitamin K2 exhibited more potent efficacy in the treatment of postmenopausal
osteoporosis, more effectively enhancing BMD and bone metabolism markers than
vitamin K2 alone, without a significant increase in adverse reactions.
Asymmetric Alkyl-Alkyl Cross-Coupling Enabled by Ni-Catalyzed Cross-Hydrodimerization of Enamides with Unactivated Alkenes
Authors: Shu Wei , Yang Peng-Fei , Zhao Han-Tong
Published: August 2024

Saturated stereogenic centers containing C(sp3)–C(sp3) bonds comprise a major portion of organic molecules. Over the past decades, transition-metal-catalyzed asymmetric C(sp3)–C(sp3) cross-coupling has evolved into an efficient strategy for constructing such stereogenic centers. However, reaction modes to build asymmetric C(sp3)–C(sp3) bonds remain limited. Herein, a nickel-catalyzed enantioselective cross-hydrodimerization between distinct alkenes to enable the enantioselective construction of alkyl–alkyl bonds has been developed. In this reaction mode, N-acyl enamines (enamides) and unactivated alkenes undergo oxidative enantioselective cross-hydrodimerization with excellent levels of chemo- and head-to-tail regioselectivity to give enantioenriched N-acyl α-branched amines by forging the C(sp3)–C(sp3) bond with control of the enantioselectivity. The presence of both reducing and oxidizing reagents in the reaction allows the use of alkenes as sole precursors to forge enantioselective C(sp3)–C(sp3) bonds, representing a new reaction mode for asymmetric alkyl–alkyl cross-coupling. The asymmetric cross-hydrodimerization between distinct alkenes provides a new strategy for constructing saturated stereogenic centers containing C(sp3)–C(sp3) bonds.
Adjustable stereo path design method based on pin-sculpture acoustic topological insulator with Z-dislocation defect immunity
Authors: Liu Peng , Li Hangyu , Lv Zengyao , Pei Yongmao
Published: August 2024

The field of topological protected wave engineering, inspired by quantum mechanics, has generated significant interest. Acoustic analogs of electronic topological insulators provide new opportunities for manipulating sound propagation with unconventional acoustic edge modes that are immune to backscattering. Numerous reports have been published on the design of two-dimensional acoustic topological insulators (ATIs). However, the sound path of a two-dimensional design is simple, and its ability to control sound waves is limited. On the other hand, the design of 3D ATIs is relatively complex, making it difficult to manufacture and limiting its versatility. Based on the design idea of the 2D ATIs, inspired by the art named 3D pin-sculpture, an adjustable structure of a finite size consisting of spindle-shaped units with a variable cross section is designed to realize flexible path transformation. Furthermore, unlike two-dimensional structural defects, such as cavities and disorder, the analysis of vertical dislocation defects in finite-sized structures allows for the design of local sound propagation along the z-direction, providing a concept for constructing a stereo path. The designed structure also serves two functions: acoustic switch and delay. This idea offers an alternative approach to designing complex sound transmission paths.
Automatic driving image matching via Random Sample Consensus (RANSAC) and Spectral Clustering (SC) with monocular camera
Authors: You Hairong , Xie Yang
Published: August 2024

In today’s big data era, with the development of the Internet of Things (IoT) technology and the trend of autonomous driving prevailing, visual information has shown a blowout increase, but most image matching algorithms have problems such as low accuracy and low inlier rates, resulting in insufficient information. In order to solve the problem of low image matching accuracy and low inlier rate in the field of autonomous driving, this research innovatively applies spectral clustering (SC) in the field of data analysis to image matching in the field of autonomous driving, and a new image matching algorithm “SC-RANSAC” based on SC and Random Sample Consensus (RANSAC) is proposed. The datasets in this research are collected based on the monocular cameras of autonomous driving cars. We use RANSAC to obtain the initial inlier set and the SC algorithm to filter RANSAC’s outliers and then use the filtered inliers as the final inlier set. In order to verify the effectiveness of the algorithm, it shows the matching effect from three angles: camera translation, rotation, and rotation and translation. SC-RANSAC is also compared with RANSAC, graph-cut RANSAC, and marginalizing sample consensus by using two different types of datasets. Finally, we select three representative pictures to test the robustness of the SC-RANSAC algorithm. The experimental results show that SC-RANSAC can effectively and reliably eliminate mismatches in the initial matching results; has a high inlier rate, real-time performance, and robustness; and can be effectively applied in the environment of autonomous driving.
Rayleigh–Taylor turbulence in strongly coupled dusty plasmas
Authors: Wani Rauoof , Verma Mahendra , Tiwari Sanat
Published: August 2024

The turbulence mixing initiated by the Rayleigh–Taylor instability has been reported in a two-dimensional (2D) strongly coupled dusty plasma system using classical molecular dynamics simulation. The entire evolution cycle, including the initial equilibrium, the instability, turbulent mixing, and, finally, a new equilibrium through the thermalization process, has been demonstrated via the respective energy spectra. The fully developed spectrum follows the Bolgiano-Obukho k−11/5 scaling at smaller wavenumbers, a characteristic 2D buoyancy-driven turbulent flow feature. At higher wavenumbers, the energy spectrum E(k)∝k represents the thermalization of the system and is a characteristic feature of 2D Euler turbulence. At longer timescales, the system reflects the Kolmogorov scale of k−3. Moreover, strong coupling slows the turbulent mixing process, though the final state is a complete thermalized system. Our results also help us to understand the thermalization process in Yukawa fluids, other strongly coupled plasma families, and turbulent mixing in low Reynolds number fluids.
Surface gravity wave interaction with a floating circular elastic plate in the presence of concentric porous arc walls
Authors: Negi P. , Sahoo T. , Meylan M. H.
Published: August 2024

A Fourier Bessel series type expansion formula is used to investigate the interaction of surface gravity wave with two arc-shaped porous breakwaters that shield a circular floating flexible structure from wave action. The flexural gravity waves result from the interaction between the surface gravity waves and the circular floating structure. Additionally, when the floating structure encounters lateral compression force, flexural gravity wave blocking occurs. Moreover, the floating structure is triggered by the interaction of three unique wave modes for every wave frequency within the confines of the blocking frequencies. The two arc-shaped permeable breakwaters significantly reduce the wave force acting on the floating structure as compared to situations where there is just one arc wall or no breakwater at all. Resonant peaks in the wave forces arising within the impermeable breakwaters diminish with the introduction of structural permeability. The hydrodynamic load on the floating structure and the pair of porous arc breakwaters exhibit removable discontinuities near the blocking frequency. Surface plots illustrate the irregular distribution of plate deflection at certain angular frequencies. Contour plots are used to ascertain the spatial configuration of fluid flow around a structure. Furthermore, several wave and structural parameters, including the position of the breakwaters and their structural dimensions, breakwater porosity, annular radius, compressive force, incident angle, and wave forces experienced by the floating structure, contribute to mitigating wave-induced structural response and wave forces experienced by the floating structure. Time-dependent simulation of the surface displacement by the incident wave demonstrates the flow features.
Accurate and rapid reactive flow simulations using dynamic load balancing and sparse analytical Jacobian approach
Authors: Yang Yinan , Hori Tsukasa , Sawada Shinya , Akamatsu Fumiteru
Published: August 2024

The present study introduces a rapid and accurate customized solver on the OpenFOAM platform for large-scale industrial computations. Specifically, a sparse analytical Jacobian approach utilizing the SpeedCHEM library was implemented to enhance the efficiency of the ordinary differential equation solver. The dynamic load balancing code was used to distribute computational workloads uniformly across multiple processes. Optimization continued with open multi-processing to improve parallel computing efficiency and the local time stepping scheme to maximize individual cell time steps. The effectiveness and robustness of the customized solver were first validated using Sandia flames D–F as benchmarks. The results showed that the customized solver exhibited better strong scaling characteristics and led to a speed increase of up to 30 times for two-dimensional Sandia flame D calculations. The numerical predictions for temperature and species distribution closely matched the experimental trends, confirming the accuracy of the solver. Subsequently, a three-dimensional numerical study on a 10 kW ammonia co-combustion furnace was conducted, exploring the performance of the solver in large-scale reactive simulations. Results analysis indicated that the acceleration capability was reduced due to increased communication overhead between processors, achieving up to 7.06 times speed-up. However, as the size of the reaction mechanism increases, better acceleration capabilities can be demonstrated. The numerical predictions could closely replicate experimental trends, effectively predicting NO emission trends within the combustion furnace. This study offers one viable solution for rapid and accurate calculations in the OpenFOAM platform, which could be applied in the subsequent ammonia industrial combustion processes.
Probabilistic modeling of energy transfer in disordered organic semiconductors
Authors: Valente Gustavo Targino , Gontijo Guimarães Francisco Eduardo
Published: August 2024

The non-radiative energy transfer process governs the transport of excitons in organic semiconductors, directly affecting the performance of organic optoelectronic devices. Successful models describe this transfer in terms of energy donor–acceptor pair sites, in contrast to experimental photophysical properties, which reflect the average behavior of the molecular ensemble. In this study, an energetic and spatial probability density function is proposed to determine the average non-radiative energy rate for homotransfer processes. This approach considers the energetic-spatial distribution typical of disordered semiconducting polymers. The average homotransfer rate is significantly dependent on the energy of the donor site, allowing the identification of the photophysical process most likely to occur. Values of the order of 1011 s−1 were predicted and are consistent with experimental results. This approach was used to evaluate how the energy transfer efficiency in heterostructures is affected by the energy and position of the energy donor site. The model presented in this study can be explored in other organic systems to investigate exciton transport mechanisms in new organic optoelectronic device architectures.
A method to obtain the trapping energy and trapping range between hydrogen and defects at finite temperature
Authors: Ming Zhengyang , Chen Ze , Wang Zhaofan , Yin Chao , Mao Shifeng , Ye Minyou
Published: August 2024

The binding energy between hydrogen (H) and defects in solid phase materials has been widely studied, which is of vital importance to understand the H retention effects and defect growth mechanisms. However, present studies of binding energy through density functional theory (DFT) or the molecular statics (MS) method were usually performed at 0 K, which could not take the influence of entropy into consideration. In this work, a thermodynamic method has been proposed to obtain the trapping energy between H and defects at finite temperatures. The method is based on the rate theory, which uses trapping energy (V) and trapping range (δ) to describe the trapping properties of defects. Ultimately, a parameterized H spatial cumulative distribution function at thermodynamic equilibrium state could be given. The trapping energy and trapping range parameters in the function can be determined by contrast with the results obtained from molecular dynamics or other methods. This method has been applied to calculate the trapping energies and trapping ranges of H to helium bubble and grain boundary, respectively. Further discussion has been made on the discrepancy between trapping energies obtained by this method and the conventional DFT/MS method.
Anomalous photo-thermoelectric effects of platinum and tungsten trioxide bilayers
Authors: Ito Takeru , Hanioka Chihiro , Irie Hiroshi
Published: August 2024

We attempted to deposit a platinum (Pt) layer onto a tungsten trioxide (WO3) thin film (Pt/WO3). The Pt layer deposited on WO3 was oxidized by calcining Pt/WO3 in air to form PtOx/WO3. An n-type anomalous photo-thermoelectric (photo-TE) effect was confirmed for Pt/WO3 and Pt/HyWO3−x. HyWO3−x is a protonated WO3 after the gaschromic (GC) reaction of WO3 in Pt/WO3. The anomalous photo-TE effect was that both the electrical conductivity (σphoto) and the absolute value of the Seebeck coefficient (Sphoto) increased under UV light or visible light irradiation. After stopping the irradiation, σphoto and Sphoto decreased. In contrast, an n-type normal photo-TE effect was observed for PtOx/HyWO3−x after the GC reaction of PtOx/WO3, in which σphoto increased and the absolute value of Sphoto decreased under ultraviolet (UV) light irradiation, and vice versa after stopping the irradiation. These findings indicate that Pt was responsible for the anomalous photo-TE effect due to the electron accumulation capability of Pt, to which electrons were transferred from the conduction band of HyWO3−x. In contrast, electrons could not energetically transfer from HyWO3−x to PtO2, which existed in PtOx particles at the surface. Therefore, PtOx/HyWO3−x behaved similar to sole HyWO3−x, indicating the normal photo-TE effect.
Role of very large-scale motions in shock wave/turbulent boundary layer interactions
Authors: Fan Jianhui , Hao Jiaao , Wen Chih-Yung
Published: August 2024

The present study investigates the cause of low-frequency unsteadiness in shock wave/turbulent boundary layer (TBL) interactions. A supersonic turbulent flow over a compression ramp is studied using wall-resolved large eddy simulation (LES) with a freestream Mach number of 2.95 and a Reynolds number (based on δ0: the thickness of the incoming TBL) of 63 560. From the view of stability analysis, the effect of intrinsic instability on such low-frequency unsteadiness is excluded from the flow system by designing a ramp angle of 15°, and our attention is paid to the convective instability contributed by the incoming TBL. The LES results are analyzed by linear and nonlinear disambiguation optimization (LANDO), spectral proper orthogonal decomposition (SPOD), and resolvent analysis. The LANDO results reveal a streamwise scale-frequency relation of coherent structures in a very long (around 60δ0) TBL, which indicates that the dynamics of very large-scale motions (VLSMs) in the TBL are featured by a low frequency. The SPOD results reveal that the most energetic SPOD mode features a low frequency that is identical to the dominant low frequency of the wall-pressure spectrum. Additionally, coherent structures of the mode resemble the VLSMs in the incoming TBL. These consistencies imply that the dynamics of VLSMs contribute to the low-frequency unsteadiness of the present flow. A resolvent analysis then further suggests that the origins of low-frequency dynamics of the present flow are from the VLSMs, which can be optimally amplified by the forcing in the turbulent flow.
Transient surface pressure of a rectangular cylinder subjected to downburst-like winds
Authors: Li Shaopeng , Peng Liuliu , Yang Qingshan , Li Xin , Cao Jinxin , Cao Shuyang , Jiang Yan
Published: August 2024

Thunderstorm downbursts are transient in nature and have been responsible for a variety of structural damages in recent years. Currently, the researchers have done several works on the characteristics of downburst wind speed. Nonetheless, rare attention has been placed on the structural aerodynamics characteristics subjected to downburst winds. Based on this, an experimental investigation is performed to reproduce downburst-like winds physically and to study the transient surface pressures (SPs) on a 5:1 rectangular cylinder (RC). The experiment is conducted within a multiple-fan active control wind tunnel (MFACWT) and mainly focuses on simulating the transient characteristics of downburst-like flow, including time-varying mean (TVM) wind speed and nonstationary wind fluctuation. The resulting SPs are measured to understand the influence of transient wind on the aerodynamic behavior of bluff bodies. The spatiotemporal characteristics of the SPs are analyzed using wavelet transform and Priestley's classic spectral theory. The results indicate that the transient nature of the downburst-like flow can be physically reproduced by a MFACWT. The instantaneous pressures of a RC are illustrated by both the turbulence parameters of the transient flow and the flow-separation characteristics. The pressure coefficients normalized by the TVM of the downburst-like winds remain constant, which provides a more appropriate way to estimate the transient gust loading in a quasi-steady manner. Interestingly, the phenomenon of the time-varying phase shift and time-varying correlation of chordwise SPs is observed when the turbulent velocity changes dramatically. In addition, the normalized surface pressure can be regarded as a stationary stochastic process, which provides a significant basis for further establishing the theoretical model of nonstationary gust-loading.
Time-dependent conduction mechanisms in reversed stepped superlattice layers of GaN HEMTs on 200 mm engineered substrates
Authors: Chen Zequan , Uren Michael J. , Huang Peng , Sanyal Indraneel , Smith Matthew D. , Vohra Anurag , Kumar Sujit , Decoutere Stefaan , Bakeroot Benoit , Kuball Martin
Published: August 2024

Time-dependent conduction in epitaxial superlattice (SL) strain relief layers of GaN high electron mobility transistors on 200 mm engineered substrates with a poly-AlN core was observed and analyzed. This phenomenon occurs when the devices were operated with substrate bias of ∼−300 V for 101–103 s. The formation of the conduction path is related to trap-assisted leakage through the SLs on the engineered substrates; de-trapped carriers spread out vertically and laterally within a portion of the SLs, leading to a higher electrical field across the rest of the layers. This conduction mechanism may be hidden during the devices' normal operation (target 650–1200 V). It could lead to undesired effects during the operation of the devices, such as a time-dependent dynamic Ron. More resistive SLs will potentially reduce the impact of this phenomenon.
Solar-driven photocatalytic nitrogen fixation on transition metal-doped covalent organic frameworks: First-principles study
Authors: Hong Wen-qing , Ao Zhi-Min , Xu Ying
Published: August 2024

Designing highly efficient single-atom catalysts for converting nitrogen into ammonia under ambient temperature conditions holds significant importance. Current research predominantly focuses on electrocatalytic nitrogen fixation, but compared to that, photocatalytic nitrogen fixation requires only sunlight as an energy source, making it more environmentally friendly and cost-effective. Developing efficient nitrogen reduction reaction (NRR) photocatalysts presents a promising yet highly challenging task. Two-dimensional (2D) covalent organic frameworks (COFs) have garnered interest because of their elevated surface area and regular pore structure. This study employs density functional theory calculations to investigate the potential of NRR photocatalysts using the 2D COF TMT-TFPT-COF (TT-COF) supported with 18 different transition metal atoms (TM = Rh, Nb, Os, Mo, Ru, Pt, Ni, Co, V, Cu, Fe, Re, W, Cr, Ta, Mn, Pd, Ti). Through a four-step selection process, the most promising photocatalyst is identified. The results indicate that a single Re atom loaded onto TT-COF (Re@TT-COF) displays the optimal nitrogen fixation performance, demonstrating excellent catalytic activity and selectivity with a limiting potential of only −0.30 V. Furthermore, its good light absorption efficiency, suitable band edge position, and significant photo-generated electron potential enable spontaneous nitrogen fixation. Our study provides useful guidance for the rational design of COF-based NRR photocatalysts with high activity, stability, and selectivity.
Numerical study of the interaction between cylindrical particles and shear-thinning fluids in a linear shear flow
Authors: Ji Jingbo , Zhang Hao , An Xizhong , Yang Dongmin
Published: August 2024

In this paper, the interaction between cylindrical particles and shear-thinning non-Newtonian fluids in a linear shear flow is investigated using particle-resolved direct numerical simulation. The Carreau model is used to represent the rheological properties of shear-thinning fluids, and the numerical method is validated against previously published data. Then, the effects of Reynolds number (Re), aspect ratio (Ar), power-law index (n), Carreau number (Cu), and incident angle (α) on drag coefficient (CD), lift coefficient (CL), and torque coefficient (CT) of cylindrical particles are investigated. The numerical results show that the flow field structure and pressure distribution around the cylindrical particle in a shear flow are different from those in a uniform flow, and the particles in a shear flow generate extra CL and CT. Furthermore, comparing with Newtonian fluids, the shear-thinning properties of the non-Newtonian fluid change the viscosity distribution and significantly decrease the CD, CL, and CT of the particles. The variation laws and influencing mechanisms of CD, CL, and CT under different working conditions are discussed by dividing the total coefficients into pressure and viscous shear contributions. Predictive correlations of CD, CL, and CT are established by considering the effects of Re, Ar, n, Cu, and α. The findings indicate that both the shear flow mode and shear-thinning properties must be considered when evaluating relevant particle–fluid interactions, which provides important guidance for predicting and controlling the orientation and distribution of cylindrical particles in shear-thinning fluids. Meanwhile, the predictive correlations can be used for large-scale simulations of multiphase coupling.
Mean-flow structures of the turbulent boundary layers bounding a two-dimensional separation bubble
Authors: Bi Wei-Tao , Du Tan-Tan , Chen Jun , She Zhen-Su
Published: August 2024

Understanding the mean-flow structures of a separated turbulent boundary layer (TBL) is crucial for turbulence modeling. This study investigates the spatial scaling properties of the total shear stress and mixing length in the TBLs bounding a two-dimensional (2D) separation bubble, aiming to derive analytical descriptions for the entire mean-velocity profiles of the TBLs. For the adverse pressure gradient (APG) TBL upstream of the separation bubble, the total shear stress possesses a two-layer structure with an inner layer adhering to a linear law and an outer layer conforming to a defect power law. In contrast, the mixing length profile consists of four layers, namely the viscous sublayer, the buffer layer, the overlap layer, and the wake region. Each of the layers exhibits a power law or a defect power law relationship with the spatial coordinate normal to the wall. In the four-layer structure, three parameters are sensitive to the variation of the APG: the buffer-layer thickness, the relative magnitude of the mixing length at the boundary layer edge, and a defect power law exponent quantifying the extent of the wake region. For the reattached TBL downstream of the separation bubble, the total shear stress consists of two parts. One part is induced by the pressure gradient and retains the two-layer structure, while the other, engendered by the intense turbulence advected from the separated shear layer, exhibits a dual-power-law distribution. The advected turbulence also significantly alters the four-layer structure of the mixing length, resulting in an augmented buffer layer, a diminished overlap layer, and a wake region that mimics a turbulent mixing layer. Via a dilation ansatz to describe the scaling transition between adjacent layers, the study formulates the complete profiles of the total shear stress and mixing length. The formulation leads to the derivation of novel analytical expressions for the entire mean-velocity profiles of the TBLs. The expressions are in precise accord with the direct numerical simulations of an incompressible 2D separation-bubble flow and a 2D impinging shock wave/TBL interaction. The elucidation of the mean-flow structures through this study is anticipated to facilitate the analysis of turbulence models, thereby enhancing their performance in simulating separated TBLs. The construction of the mean-flow descriptions by inspecting the spatial scaling properties of turbulence paves a promising way for theoretical exploration of complex nonequilibrium TBLs.
Models to predict configurational adiabats of Lennard-Jones fluids and their transport coefficients
Authors: Heyes D. M. , Dini D. , Pieprzyk S. , Brańka A. C. , Costigliola L.
Published: August 2024

A comparison is made between three simple approximate formulas for the configurational adiabat (i.e., constant excess entropy, sex) lines in a Lennard-Jones (LJ) fluid, one of which is an analytic formula based on a harmonic approximation, which was derived by Heyes et al. [J. Chem. Phys. 159, 224504 (2023)] (analytic isomorph line, AIL). Another is where the density is normalized by the freezing density at that temperature (freezing isomorph line, FIL). It is found that the AIL formula and the average of the freezing density and the melting density (“FMIL”) are configurational adiabats at all densities essentially down to the liquid–vapor binodal. The FIL approximation departs from a configurational adiabat in the vicinity of the liquid–vapor binodal close to the freezing line. The self-diffusion coefficient, D, shear viscosity, ηs, and thermal conductivity, λ, in macroscopic reduced units are essentially constant along the AIL and FMIL at all fluid densities and temperatures, but departures from this trend are found along the FIL at high liquid state densities near the liquid–vapor binodal. This supports growing evidence that for simple model systems with no or few internal degrees of freedom, isodynes are lines of constant excess entropy. It is shown that for the LJ fluid, ηs and D can be predicted accurately by an essentially analytic procedure from the high temperature limiting inverse power fluid values (apart from at very low densities), and this is demonstrated quite well also for the experimental argon viscosity.
Study on transient cavitation performance of centrifugal pump based on the influence of rough impeller
Authors: Gu Jintong , Sun Huihui , Yao Yuan , Chen Qing , Zeng Yong , Lu Qian , Fu Shifeng
Published: August 2024

This study employs numerical simulation to investigate the transient flow and cavitation performance of centrifugal pumps with rough impellers, validating the numerical method with experimental data. Initially, the effect of blade roughness on the external characteristics of centrifugal pumps is examined. Subsequently, the study specifically addresses the impact of roughness on internal flow characteristics during cavitation, including vapor volume distribution, three-dimensional vortex structures, and vorticity distribution in the impeller channel. Furthermore, the influence of blade roughness on local energy loss is analyzed using entropy production theory. Finally, several monitoring points are arranged in the impeller channel to assess pressure pulsation effects. The results show that blade roughness generally reduces the head and efficiency of centrifugal pumps. During the non-cavitation and cavitation incipient stages, roughness marginally increases the head, with a maximum increase in only 0.1%. Impeller roughness causes vacuole collapse and vortex structure enlargement, disrupting the stable flow path within the channel. Blade roughness also escalates energy loss within impeller components, particularly under full cavitation conditions, where the impeller's entropy production accounts for up to 50%. Pressure pulsation results reveal that while blade roughness can slightly suppress cavitation, it also disturbs the flow field pressure. These insights provide guidance and data support for mitigating roughness and cavitation, the two primary instability factors in centrifugal pump operations.
Scalar gravitational Aharonov–Bohm effect: Generalization of the gravitational redshift
Authors: Tobar Michael E. , Hatzon Michael T. , Flower Graeme R. , Goryachev Maxim
Published: August 2024

The Aharonov–Bohm effect is a quantum mechanical phenomenon that demonstrates how potentials can have observable effects even when the classical fields associated with those potentials are absent. Initially proposed for electromagnetic interactions, this effect has been experimentally confirmed and extensively studied over the years. More recently, the effect has been observed in the context of gravitational interactions using atom interferometry. Additionally, recent predictions suggest that temporal variations in the phase of an electron wave function will induce modulation sidebands in the energy levels of an atomic clock, solely driven by a time-varying scalar gravitational potential. In this study, we consider the atomic clock as a two-level system undergoing continuous Rabi oscillations between the electron's ground and excited state. We assume the photons driving the transition are precisely frequency-stabilized to match the transition, enabling accurate clock comparisons. Our analysis takes into account, that when an atom transitions from its ground state to an excited state, it absorbs energy, increasing its mass according to the mass-energy equivalence principle. Due to the mass difference between the two energy levels, we predict that an atomic clock in an eccentric orbit experiencing a time-varying gravitational potential, will exhibit a constant frequency redshift relative to a ground clock, corresponding to the orbit's average gravitational redshift. Additionally, modulation sidebands will appear, and detecting these predicted sidebands would confirm the scalar gravitational Aharonov–Bohm effect.
Does the selection of the fracture model affect the calculation of the permeability of a rock mass?
Authors: Guo Jichao , Zheng Jun , Wang Jiawei , Lü Qing , Deng Jianhui
Published: August 2024

The permeability of a rock mass is an indispensable and significant parameter for the construction of rock engineering. Since most fractures are buried in the rock mass, accurately assessing the permeability of the rock mass has posed a challenge to scholars in the field. The discrete fracture network (DFN) is recognized as an effective method for calculating the permeability of rock masses. However, the impact of the fracture model on permeability calculations is neglected during the construction of DFNs. This study uses the FracMan software to conduct a series of numerical simulation experiments, demonstrating that the selection of the fracture model significantly influences permeability calculations. Furthermore, we investigate the effects of constructing different circular DFNs based on trace information from various sampling windows. The results indicate that relying solely on a circular DFN derived from a single sampling window to calculate permeability is unreliable, and we reveal the fundamental laws of how DFNs constructed based on different fracture models influence the permeability assessment of rock masses. Therefore, integrating multi-source information from rock mass outcrops and boreholes, in conjunction with selecting an appropriate fracture model for constructing DFNs, is crucial for accurate permeability calculations of rock masses.
Using exploratory modeling to challenge narratives of risk governance in Mexico City
Authors: Eakin Hallie , Bojórquez-Tapia Luis A. , Miquelajauregui Yosune , Grave Ileana , Aguilar Bertha Hernandez , Janssen Marco A.
Published: August 2024

Achieving more sustainable adaptation to social–environmental change demands the transformation of the narratives that provide the rationale for risk governance. These narratives often reflect long-standing beliefs about social and political relationships, ascribe actions and responsibilities, and specify solutions to risk. When such solutions are implemented through material investments in landscapes, these narratives become embedded in physical infrastructure with long legacies. Dominant narratives can mask a range of divergent problem framings. By masking alternatives, narratives can contribute to the persistence of unsustainable governance trajectories. Decision-support tools have begun to represent narratives as drivers of system dynamics; making narratives visible can reveal opportunities for more sustainable governance. We present the results of the project “The Dynamics of Multi-Scalar Adaptation in the Megalopolis”, a dynamic, exploratory model of socio-hydrological risks in Mexico City that was designed to both endogenize and simultaneously challenge the dominant narratives that characterize water-risk governance in the city. Qualitative data characterize dominant narratives at city and borough scales. An agent-based model, informed by multicriteria decision analysis and coupled with hydrological, urbanization, and climatic model inputs, permitted the development of exploratory governance scenarios designed to challenge dominant narratives. Scenarios revealed how dominant narratives may contribute to the persistence of vulnerability “hotspots” in the city, despite stated goals of equity and vulnerability alleviation. Participatory workshops with representatives of the city government illustrate how making such narratives visible through exploratory modeling can lead to a questioning of prior assumptions and causal relations, recognition of a need for intersectoral collaboration, and insights into potential management strategies.
Syntax and semantics of Role Shift in Japanese Sign Language
Authors: Kawasaki Noriko
Published: August 2024

This article argues that Role Shift in Japanese Sign Language involves a mechanism that is different in two respects from indexical shift observed in some spoken languages. First, its domain is not a clausal domain (CP or IP), but the thematic (propositional) domain, in which thematic roles are assigned. Second, what is shifted by this mechanism is not indexicals, but the objective Point-of-View from which the reported event is perceived. These characteristics apply to both Action Role Shift and Quotational Role Shift. It is claimed that Quotational Role Shift is a subcase of Action Role Shift where the thematic domain contains a predicate of propositional attitude. The attitude predicate takes a CP complement which in turn contains another operator. This second operator is the same as that found in some spoken languages, and it shifts the context for the interpretation of indexicals. The proposed analysis thus employs two types of operators, one taking the thematic domain as its scope and the other operating on the clausal domain. The analysis can be extended to account for crosslinguistic variation reported on the shifted interpretation of locative/temporal expressions in sign languages.