bluuebunny/crossref_metadata_2025 huggingface dataset:
Visual Outcomes after Suprasellar Meningioma Resection: A Retrospective Cohort Study and a Machine Learning-Based Predictive Model
Authors: Iranmehr Arad , Chavoshi Mohammadreza , Zeinalizadeh Mehdi
Published: February 2024

Objectives In this research, the authors provide a retrospective cohort study of 82 patients with suprasellar meningiomas to identify predictors of the visual outcome following surgery. We also conducted a matched retrospective case–control analysis.

Methods This retrospective cohort study included all patients who underwent craniotomy for surgical excision of suprasellar meningiomas at our institution between January 2016 and March 2022. We designed a matched case–control study for patients with and without early intradural optic canal decompression (IOCD). We also developed a machine learning model to have the best possible sensitivity for the prediction of visual recovery after surgery.

Results The visual acuity score (VAS) improved in 46.3% of our cases and decreased in 7.4% of the 82 included cases postoperatively. The VAS did not change in 46.3% of the patients after surgery. Statistically, visual complaints, optic atrophy, tuberculum sella involvement, and olfactory groove involvement were associated with lower preoperative VAS and visual field index (VFI). Only intracavernous sinus (ICS) extension and intraoperative vascular involvement were significantly associated with lower postoperative mean VAS correction. The outcome analysis revealed that the improvement in VAS and VFI after surgery was not statistically different between the groups with and without early IOCD (p-value = 1).

Conclusion ICS extension was the only location-related factor associated with increased tumor recurrence or regrowth, which makes postoperative radiotherapy more valuable in patients with cavernous sinus extension. Our study results did not support the efficacy of early IOCD in increasing postoperative VAS and VFI.
Being and timeouts: live sports in the psyche
Authors: Engley Ryan
Published: February 2024

Despite televised sports being a non-fiction event, the gap that separates a sporting event’s live unfolding from its televisual transmission ensures that it has all the aesthetic dynamism of a dramatic series. This essay argues that the sense of liveness that undergirds a televised sports broadcast operates on the side of the viewing subject rather in the object itself. It is the psyche that makes sport live—not the broadcast. This essay looks to Freudian and Lacanian concepts and ideas from television studies to concretize its theoretical intervention.
The level of conscientiousness trait and technostress: a moderated mediation model
Authors: Ariño-Mateo Eva , Venegas Matías Arriagada , Mora-Luis Carlos , Pérez-Jorge David
Published: February 2024

As organizations increasingly rely on technology for the management, planning, and execution of activities and tasks. The consequence of technology use is technostress, which can ultimately affect workers’ mental and physical health. This study aimed to explore the factors influencing technostress in relation to conscientiousness and the mediating effects of organizational dehumanization based on hierarchical levels within the organization. The sample consisted of 190 adults, with the majority being teachers (57.4%). A moderated mediation analysis was employed using the PROCESS software. This study reveals that organizational dehumanization is a mechanism through which conscientiousness can foster technostress, mainly when the hierarchy level is situated at lower levels. Organizations should develop an approach to addressing technostress based on the hierarchical roles and competencies assumed by workers to promote healthier work environments and decrease the stress caused by technology.
Mapping the evolution of algorithmic HRM (AHRM): a multidisciplinary synthesis
Authors: Cameron Roslyn , Herrmann Heinz , Nankervis Alan
Published: February 2024

High levels of confusion persist around the term “algorithm” in general; and in addition to this, there is also conceptual confusion around the application of algorithms to human resource management (HRM) strategy and functions. Although there are several systematic reviews of various algorithmic applications to HRM and many of its functions, no comprehensive evolutionary map of the emergent field of algorithmic HRM (AHRM) could be found in the academic literature. This study has dual aims. The first is to provide conceptual clarity for the field of AHRM, and the second is to map the evolution of AHRM from 2000 to 2022. To address the first aim, we conduct a multidisciplinary synthesis of the concepts related to algorithms which results in a General Framework for Algorithmic Decision-Making. This framework then informs the empirical part of the study which addresses the second aim. A science mapping review is employed to chart and assess the extant literature on algorithmic HRM from 2000 to 2022. This study presents a General Framework for Algorithmic Decision-Making across all business functions and then a Framework for Algorithmic AHRM Tools. This provides conceptual clarity and distinguishes between automated and augmented HR decision-making. Findings also reveal the multidisciplinary nature of this emergent field of inquiry and point to current research, which focuses on specialized applications for HR functions such as workforce planning, learning and development, allocation and scheduling, and recruitment; but lacks emphasis on more integrative strategic HRM contexts. The study also has implications for organizational strategic decision-making. HR practitioners may need to form project teams with their information technology (IT) and data analyst colleagues when making strategic decisions about algorithmic applications for HR strategy and HR functions. This also lends itself to future research with multidisciplinary research teams including HR researchers along with computer scientists, computational engineers, and data analysts.
Civil liability for the actions of autonomous AI in healthcare: an invitation to further contemplation
Authors: Eldakak Ahmed , Alremeithi Abdulla , Dahiyat Emad , El-Gheriani Moatasem , Mohamed Hassan , Abdulrahim Abdulla Mohammad Ibrahim
Published: February 2024

There are already a number of autonomous robots that play a significant role in improving the quality of healthcare in different areas ranging from basic health diagnosis to complex surgeries. However, using robots and machine learning applications in the healthcare context poses concerns over liability for patient injury. This paper will thus attempt to investigate the potential legal problems that might arise if AI technology evolves or is commonly used in clinical practice. It also examines whether the traditional doctrines of liability can adequately address the liability for the injuries stemming from acts of autonomous robots. As such, this paper adopted both descriptive and analytical methodologies to explore the main focus of the study. while the descriptive methodology was used to spot light on various theories of liability, the analytical methodology was used to critically examine the main theories that have been advanced to deal with autonomous robots and predict the necessity of legal reform. Throughout this paper, the authors insist on the importance of distinguishing between robots in light of their degree of autonomy and then drafting liability rules depending on whether the action was done autonomously by an unattended robot or whether it was done automatically by an attended robot. Finally, the paper concludes with the proposal of a series of factors to be considered for the future regulation of AI Robots in the healthcare context.
Teachers’ perceived work ability: a qualitative exploration using the Job Demands-Resources model
Authors: Hlado Petr , Harvankova Klara
Published: February 2024

Teaching is a highly demanding profession; therefore, it is necessary to address how teachers cope with the demands of their job and how these demands affect their work ability. This study aims to investigate teachers’ perceptions of work ability and the underlying mechanisms through which job demands influence their perceived work ability. The Job Demands-Resources (JD-R) model serves as the theoretical framework for this investigation. A qualitative approach was employed, utilizing in-depth interviews with a sample of 14 upper secondary school teachers in the Czech Republic. The teachers had an average age of 46.9 years (SD = 9.22). The findings revealed a limited awareness among teachers regarding the holistic nature of work ability. Job demands emerged as a factor indirectly impacting perceived work ability through the health impairment process. High job demands and obstacles contributed to teacher stress, resulting in fatigue, impaired physical or mental health, and reduced perceived work ability. Moreover, the study showed how tough job demands extend beyond the professional realm, leading to work-family conflicts that further impair work ability. This study provided empirical support for the inclusion of perceived work ability as an outcome influenced by job demands within the JD-R model. Additionally, it emphasized the need for a comprehensive framework that considers both organizational and individual factors in both work and non-work domains to effectively investigate perceived work ability among teachers.
The appeal of the circular economy revisited: on track for transformative change or enabler of moral licensing?
Authors: Eickhoff Hans
Published: February 2024

The proposal of an economy that is circular and without the need for material or energy input has an irresistible appeal to those who recognize the precautionary concept of planetary boundaries and acknowledge that resources are limited. Thus, in the public discourse, its narrative outperforms other lines of arguments when it comes to keeping radical critics of destructive extractivism and the growth imperative in check and averting discussion of degrowth, post-growth, or other systemic alternatives by larger segments of the population and government bodies. Moreover, the myth of a circular economy has the additional benefit that it can win over parts of the environmental movement that is apprehensive of radical and transformative change, particularly in the urban milieus of a middle class that enjoys the privileges of the current social order. In this paper, I argue that the circular economy narrative tends to hinder the necessary systemic transformation while entailing a wide range of specific measures that deserve to be recognized for their merit.
Spatial–temporal characterization of photoemission in a streak-mode dynamic transmission electron microscope
Authors: Roy Moulik Samik , Lai Yingming , Amini Aida , Soucy Patrick , Beyerlein Kenneth R. , Liang Jinyang
Published: February 2024

A long-standing motivation driving high-speed electron microscopy development is to capture phase transformations and material dynamics in real time with high spatial and temporal resolution. Current dynamic transmission electron microscopes (DTEMs) are limited to nanosecond temporal resolution and the ability to capture only a few frames of a transient event. With the motivation to overcome these limitations, we present our progress in developing a streak-mode DTEM (SM-DTEM) and demonstrate the recovery of picosecond images with high frame sequence depth. We first demonstrate that a zero-dimensional (0D) SM-DTEM can provide temporal information on any local region of interest with a 0.37 μm diameter, a 20-GHz sampling rate, and 1200 data points in the recorded trace. We use this method to characterize the temporal profile of the photoemitted electron pulse, finding that it deviates from the incident ultraviolet laser pulse and contains an unexpected peak near its onset. Then, we demonstrate a two-dimensional (2D) SM-DTEM, which uses compressed-sensing-based tomographic imaging to recover a full spatiotemporal photoemission profile over a 1.85-μm-diameter field of view with nanoscale spatial resolution, 370-ps inter-frame interval, and 140-frame sequence depth in a 50-ns time window. Finally, a perspective is given on the instrumental modifications necessary to further develop this promising technique with the goal of decreasing the time to capture a 2D SM-DTEM dataset.
Microscopic nonlinear optical response: Analysis and calculations with the Floquet–Bloch formalism
Authors: Popova-Gorelova Daria , Santra Robin
Published: February 2024

We analyze microscopic nonlinear optical response of periodic structures within the Floquet–Bloch formalism. The analysis is focused on the real-space distributions of optically induced charge and electron current density within the unit cell of a crystal. We demonstrate that the time-reversal symmetry of a crystal determines the phases of the temporal oscillations of these distributions. We further analyze their spatial symmetries and connection to macroscopic optical response. We illustrate our study with ab initio calculations that combine density functional theory with the Floquet–Bloch formalism. The calculations provide time-dependent optically induced charge distributions and electron current densities within the unit cells of a crystal with inversion symmetry MgO and a crystal without inversion symmetry GaAs in response to a strong-field excitation. The real-space, microscopic view on nonlinear optical response provides insightful information about the strong field–matter interaction.
Ionization and neutral gas heating efficiency in radio frequency electrothermal microthrusters: The role of driving frequency
Authors: Leigh Sid , Doyle Scott J. , Smith Gregory J. , Gibson Andrew R. , Boswell Rod W. , Charles Christine , Dedrick James P.
Published: February 2024

The development of compact, low power, charge–neutral propulsion sources is of significant recent interest due to the rising application of micro-scale satellite platforms. Among such sources, radio frequency (rf) electrothermal microthrusters present an attractive option due to their scalability, reliability, and tunable control of power coupling to the propellant. For micropropulsion applications, where available power is limited, it is of particular importance to understand how electrical power can be transferred to the propellant efficiently, a process that is underpinned by the plasma sheath dynamics. In this work, two-dimensional fluid/Monte Carlo simulations are employed to investigate the effects of applied voltage frequency on the electron, ion, and neutral heating in an rf capacitively coupled plasma microthruster operating in argon. Variations in the electron and argon ion densities and power deposition, and their consequent effect on neutral-gas heating, are investigated with relation to the phase-averaged and phase-resolved sheath dynamics for rf voltage frequencies of 6–108 MHz at 450 V. Driving voltage frequencies above 40.68 MHz exhibit enhanced volumetric ionization from bulk electrons at the expense of the ion heating efficiency. Lower driving voltage frequencies below 13.56 MHz exhibit more efficient ionization due to secondary electrons and an increasing fraction of rf power deposition into ions. Thermal efficiencies are improved by a factor of 2.5 at 6 MHz as compared to the more traditional 13.56 MHz, indicating a favorable operating regime for low power satellite applications.
Observation of non-planar dust acoustic solitary wave in a strongly coupled dusty plasma
Authors: Gogoi Prarthana , Chutia Bidyut , Sut Paragjyoti , Bailung Yoshiko , Adhikary Nirab C. , Bailung H.
Published: February 2024

The nonlinear evolution and propagation of a stable dust acoustic solitary wave (DASW) in a non-planar geometry is investigated here. The experiment is performed in a strongly coupled dusty plasma consisting of monodisperse micrometer sized particles levitated in the sheath of a capacitively coupled radio frequency argon plasma. The non-planar waves are generated with the help of a cylindrical conducting exciter pin placed at the center of the homogeneous dust cloud. A negative excitation pulse is used to create a dust void and a dust density perturbation simultaneously around the exciter. From the edge of the void, the density perturbation propagates as a nonlinear (cylindrical) non-planar DASW. The characteristics of the solitary wave are measured using image analysis of the recorded video of wave propagation. The numerical solution of the modified Korteweg–de Vries equation with an additional term to take care of the non-planar geometry is compared with the experimental observation. The wave amplitude and width are measured as a function of time and compared with the theoretical predictions.
Direct measurement of the inertial-convective subrange above ocean surface waves
Authors: Ortiz-Suslow David G. , Wang Qing
Published: February 2024

The −5/3 power law over the inertial subrange of the turbulence kinetic energy spectrum is one of the most well-known concepts in fluid physics. Obukhov and Corrsin extended the original hypothesis to a passive tracer, leading to the concept of an inertial-convective subrange. These postulates have been empirically validated in the atmospheric turbulence over land but have not been comprehensively studied in the marine air flow. During a recent oceanic campaign, the platform FLIP was deployed with an array of sensors to measure the perturbation wind velocity, temperature, and water vapor. Using these data, a previous study found that Kolmogorov's hypothesized −5/3 was not universally valid over the ocean. Here, we continue that work to analyze the spectrum of temperature and water vapor to empirically evaluate the theoretical extension by Obukhov-Corrsin. For temperature, the observed spectra were too noisy for thorough analysis; our conjecture for the source of noise and its implications for near-surface observations of atmospheric turbulence are discussed. For water vapor, we found strong agreement with the previous analysis of the kinetic energy spectrum. These findings corroborate (1) the theoretical notion of the scalar energy dissipation subrange driven by the inertial motions in the marine boundary layer and (2) evidence for non-Kolmogorov turbulence in the high Reynolds flow immediately above ocean waves. Our analysis shows a strong relationship with distance from the wavy surface; using linear extrapolation, we find that divergence from −5/3 persists in the lowest 25 m of the atmosphere.
A new generation of effective core potentials: Selected lanthanides and heavy elements
Authors: Zhou Haihan , Kincaid Benjamin , Wang Guangming , Annaberdiyev Abdulgani , Ganesh Panchapakesan , Mitas Lubos
Published: February 2024

We construct correlation-consistent effective core potentials (ccECPs) for a selected set of heavy atoms and f elements that are currently of significant interest in materials and chemical applications, including Y, Zr, Nb, Rh, Ta, Re, Pt, Gd, and Tb. As is customary, ccECPs consist of spin–orbit (SO) averaged relativistic effective potential (AREP) and effective SO terms. For the AREP part, our constructions are carried out within a relativistic coupled-cluster framework while also taking into account objective function one-particle characteristics for improved convergence in optimizations. The transferability is adjusted using binding curves of hydride and oxide molecules. We address the difficulties encountered with f elements, such as the presence of large cores and multiple near-degeneracies of excited levels. For these elements, we construct ccECPs with core–valence partitioning that includes 4f subshell in the valence space. The developed ccECPs achieve an excellent balance between accuracy, size of the valence space, and transferability and are also suitable to be used in plane wave codes with reasonable energy cutoffs.
Multi-objective optimization of a hypersonic airbreathing vehicle
Authors: Araújo Pedro P. B. , Tanaka Roberto Y. , Silva Carlos A. , Passaro Angelo , Toro Paulo G. P.
Published: February 2024

Multi-objective optimization of a hypersonic airbreathing engine (scramjet technology) was carried out with the aim of maximizing thrust and minimizing drag while satisfying a series of design constraints, such as avoiding unstart (blockage of supersonic flow within the combustion chamber) by ensuring that the pressure ratio across the shock waves remains below the adverse pressure gradient given by the Korkegi limit, geometry correction to achieve shock on-lip condition, and temperature and pressure requirements at the inlet exit. Using the relations presented in the literature, pressure and viscous drag are estimated analytically. The analytical approach is verified against computational fluid dynamics data from Ansys Fluent to solve two-dimensional compressible Reynolds-averaged Navier–Stokes flow equations, with transition shear stress transport as the turbulence closure model. Comparing the total drag and the flow properties at the combustion chamber entrance shows the model's feasibility for the optimization approach. Three different approaches were conducted to formulate the multi-objective function to determine the one that can find the highest number of geometries satisfying the Korkegi limit with the highest net thrust. The best approach was the multi-objective function formulated with the uninstalled thrust, total pressure recovery, and pressure drag, concentrating the search in the region with greater uninstalled thrust and lower drag and nearly doubling the value of net thrust compared to the first formulation, which uses the uninstalled thrust, pressure drag, and viscous drag.
Negative flows for several integrable models
Authors: Adler V. E.
Published: February 2024

A construction of negative flows for integrable systems based on the Lax representation and squared eigenfunctions is proposed. Examples considered include the Boussinesq equation and its reduction to the Sawada–Kotera and Kaup–Kupershmidt equations; one of the Drinfeld–Sokolov systems and its reduction to the Krichever–Novikov equation.
The quest for harnessing nuclear effects in graphene-based devices
Authors: Strenzke V. , Prada M. , Lopes J. M. J. , Tiemann L. , Blick R. H.
Published: February 2024

The recent successes of superconducting qubits and the demonstration of quantum supremacy over classical bits herald a new era for information processing. Yet, the field is still in its infancy and there exist viable alternative candidates that can also store quantum information. In this review, we will highlight ideas, attempts, and the experimental progress to address nuclear spins in graphene, a readily available Dirac semimetal that consists of a single layer of carbon atoms. Carbon isotopes with a nuclear spin are rare in natural graphene. However, it is possible to enrich the spin-bearing 13C isotopes to produce large-scale graphene sheets, which constitute the testbed to store, transport, and retrieve spin information, or to engineer nanostructures. Here, the hyperfine interaction between the electron spins and the nuclear spins serves as an experimental control knob and mediator to address nuclear polarization and nuclear spin coherence times through electrical measurements. The exploitation of nuclear spins in graphene is thus an alluring perspective. We will discuss methods to synthesize 13C graphene and show experimental approaches and challenges to exploit the relatively weak hyperfine interaction in two-dimensional 13C graphene devices. The ultimate purpose, i.e., the exploitation of nuclear spins in graphene for information processing, is not within reach, but its potential for future applications merits a revisit of the current state-of-the-art.
Aceh's tsunami wave evolution and its interaction with hybrid protection structure
Authors: Magdalena Ikha , Rif'atin Hany Qoshirotur , Kongko Widjo , Marta Adnan Sandy Dwi , Khoirunnisa Hanah , Nurwijayanti Amalia , Farid Mohammad
Published: February 2024

The 2004 Aceh tsunami tragedy was one of the most catastrophic occurrences, resulting in damage and severe casualties in multiple countries. This study proposes a hybrid coastal protection system made up of mangroves, a sea dike, a trench, or a combination of the three structures to prevent similar devastation in the future. This system is expected to reduce the tsunami wave height, thus lowering their potential damage. The tsunami wave propagation is reproduced using a nonlinear shallow water equation model. To construct a numerical scheme, a staggered grid finite volume method is implemented. This scheme is then validated using several benchmark tests. Once validated, the computational results are compared to experimental data collected at the Laboratory of Coastal Dynamics in Yogyakarta, Indonesia. Both the physical and numerical models use the downscaled Aceh tsunami waves and real bathymetry. Several scenarios of structures combination are presented with the aim to determine the most effective combination. A sensitivity analysis is also conducted to support the results.
Exact solutions for the probability density of various conditioned processes with an entrance boundary
Authors: Mazzolo Alain
Published: February 2024

The probability density is a fundamental quantity for characterizing diffusion processes. However, it is seldom known except in a few renowned cases, including Brownian motion and the Ornstein–Uhlenbeck process and their bridges, geometric Brownian motion, Brownian excursion, or Bessel processes. In this paper, we utilize Girsanov’s theorem, along with a variation of the method of images, to derive the exact expression of the probability density for diffusions that have one entrance boundary. Our analysis encompasses numerous families of conditioned diffusions, including the Taboo process and Brownian motion conditioned on its growth behavior, as well as the drifted Brownian meander and generalized Brownian excursion.
A user-centered smart inhaler algorithm for targeted drug delivery in juvenile onset recurrent respiratory papillomatosis treatment integrating computational fluid particle dynamics and machine learning
Authors: Islam Mohammad Rashedul , Liu Chenang , Cai Changjie , Shah Jindal , Feng Yu
Published: February 2024

Recurrent respiratory papillomatosis (RRP) is a chronic condition primarily affecting children, known as juvenile onset RRP (JORRP), caused by a viral infection. Antiviral medications have been used to reduce the need for frequent surgeries, slow the growth of papillomata, and prevent disease spread. Effective treatment of JORRP necessitates targeted drug delivery (TDD) to ensure that inhaled aerosolized drugs reach specific sites, such as the larynx and glottis, without harming healthy tissues. Using computational fluid particle dynamics (CFPD) and machine learning (ML), this study (1) investigated how drug properties and individual factors influence TDD efficiency for JORRP treatment and (2) developed personalized inhalation therapy using an ML-empowered smart inhaler control algorithm for precise medication release. This algorithm optimizes the inhaler nozzle position and diameter based on drug and patient-specific data, enhancing drug delivery to the larynx and glottis. CFPD simulations show that particle size significantly affects deposition fractions in the upper airway, emphasizing the importance of particle size selection. Additionally, optimal nozzle diameter and delivery efficiency depend on particle size, inhalation flow rate, and release time. The ML-based TDD strategy, employing a classification and regression tree model, outperforms conventional inhalation therapy by achieving a higher delivery efficiency to the larynx and glottis. This innovative concept of an ML-empowered smart inhaler represents a promising step toward personalized and precise pulmonary healthcare through inhalation therapy. It demonstrates the potential of AI-driven smart inhalers for improving the treatment outcomes of lung diseases that require TDD at designated lung sites.
Pool boiling heat transfer performance of micro-embossing molds for the fabrication of polymer wicks
Authors: Tang Heng , You Jixing , Tang Yong , Guo Bin , Sun Yalong
Published: February 2024

As flexible heat dissipation devices are urgently needed for flexible electronics, polymers with the advantages of good flexibility, insulation, and low density have attracted wide attention. It would be interesting to fabricate thermal functional structures on polymers to overcome their low thermal conductivity. This study aims to design and fabricate a micro-embossing mold to process polymer three-dimensional microgroove wicks (3D-MWs), which are applied in flexible heat pipes and achieve high thermal conductivity. Three kinds of tungsten steel molds were processed by using two wire electrical discharge machining processes (WEDM), two electrical discharge shaping machining processes (EDSM), and a combination of WEDM and EDSM. The 3D-MWs of the tungsten steel mold were reprinted onto the polymer films by a two-step embossing process. To investigate the effects of microstructures on boiling heat transfer performances, tungsten steel molds fabricated by different methods were tested to reflect the heat dissipation potential of the polymer 3D-MWs. The results showed that the 3D-MWs fabricated by the combination of WEDM and EDSM exhibit good boiling heat transfer performance and high processing efficiency, with a critical heat flux of 1040.1 kW/m2 and a maximum heat transfer coefficient of 38.4 kW/m2·°C. These values are 46% and 611% higher than those of the smooth tungsten steel surface, respectively, making it a superior choice for micro-embossing molds.
Three-component volume of fluid method coupling with interface compression method and Eulerian–Lagrangian spray atomization surface density model for prediction of cavitating sprays
Authors: McGinn P. , Tretola G. , Vogiatzaki K.
Published: February 2024

In this work, a new three phase cavitation model with Eulerian–Lagrangian Spray Atomization (ELSA) and Interface Capturing Method (ICM) coupling is presented to allow for, in a unified approach, physical insight of the surface evolution of cavitating sprays at the Sub-Grid Scale (SGS). Phase change is accounted for in the framework via mass transfer across a liquid and corresponding vapor phase. The surface density model was validated against direct numerical simulation data of an atomizing jet with a systematic variation of mesh resolutions. The sensitivity of the adjustable parameters such as the critical Weber number was also demonstrated. Then, experimental comparisons were made with a more realistic orthogonal spray geometry within a cavitating and turbulent non-cavitating system. These comparisons include both large scale visualizations and small scale SGS quantities such as the Sauter mean diameter. To our knowledge, this is the first study that presents the performance of a three phase cavitating framework with SGS ELSA-ICM coupling.
Multi-scale modeling of shock initiation of a pressed energetic material III: Effect of Arrhenius chemical kinetic rates on macro-scale shock sensitivity
Authors: Parepalli P. , Nguyen Yen T. , Sen O. , Hardin D. B. , Molek C. D. , Welle E. J. , Udaykumar H. S.
Published: February 2024

Multi-scale predictive models for the shock sensitivity of energetic materials connect energy localization (“hotspots”) in the microstructure to macro-scale detonation phenomena. Calculations of hotspot ignition and growth rely on models for chemical reaction rates expressed in Arrhenius forms; these chemical kinetic models, therefore, are foundational to the construction of physics-based, simulation-derived meso-informed closure (reactive burn) models. However, even for commonly used energetic materials (e.g., HMX in this paper) there are a wide variety of reaction rate models available. These available reaction rate models produce reaction time scales that vary by several orders of magnitude. From a multi-scale modeling standpoint, it is important to determine which model best represents the reactive response of the material. In this paper, we examine three global Arrhenius-form rate models that span the range of reaction time scales, namely, the Tarver 3-equation, the Henson 1-equation, and the Menikoff 1-equation models. They are employed in a meso-informed ignition and growth model which allows for connecting meso-scale hotspot dynamics to macro-scale shock-to-detonation transition. The ability of the three reaction models to reproduce experimentally observed sensitivity is assessed by comparing the predicted criticality envelope (Walker–Wasley curve) with experimental data for pressed HMX Class V microstructures. The results provide a guideline for model developers on the plausible range of time-to-ignition that are produced by physically correct Arrhenius rate models for HMX.
Fully discrete model of kinetic ion-induced electron emission from metal surfaces
Authors: Fernandez-Coppel Jorge , Wirz Richard , Marian Jaime
Published: February 2024

Ion-induced electron emission (IIEE) is an important process whereby ions impinging on a material surface lead to net emission of electrons into the vacuum. While relevant for multiple applications, IIEE is a critical process of electric thruster (ET) operation and testing for space propulsion, and, as such, it must be carefully quantified for safe and reliable ET performance. IIEE is a complex physical phenomenon, which involves a number of ion-material and ion-electron processes, and is a complex function of ion mass, energy, and angle, as well as host material properties, such as mass and electronic structure. In this paper, we develop a discrete model of kinetic IIEE to gain a more accurate picture of the electric thruster chamber and facility material degradation processes. The model is based on three main developments: (i) the use of modern electronic and nuclear stopping databases, (ii) the use of the stopping and range of ions in matter to track all ion and recoil trajectories inside the target material, and (iii) the use of a scattering Monte Carlo approach to track the trajectories of all mobilized electrons from the point of first energy transfer until full thermalization or escape. This represents a substantial advantage in terms of physical accuracy over existing semi-analytical models commonly used to calculate kinetic IIEE. We apply the model to Ar, Kr, and Xe irradiation of W and Fe surfaces and calculate excitation spectra as a function of ion depth, energy, and angle of incidence. We also obtain minimum threshold ion energies for net nonzero yield for each ion species in both Fe and W and calculate full IIEE yields as a function of ion energy and incidence angle. Our results can be used to assess the effect of kinetic electron emission in models of full ET facility testing and operation.
Hydraulic conveying characteristics of particles in bend based on numerical simulation and explainable stacking machine learning model
Authors: Xiao Shengpeng , Wan Chuyi , Zhou Dai , Zhu Hongbo , Bao Yan , Ji Xinran , Muwanguzi Kyazze Stephen , Han Zhaolong
Published: February 2024

As a hydraulic lifting pipeline structure widely used in deep-sea oil, gas transportation, and sediment dredging projects, the pipeline configuration is related to the improvement of transportation efficiency and pipeline safety. Particularly, the bending section consumes the most energy and withstands severe erosion. Understanding and predicting the conveying characteristics of two-phase flow in bends is therefore crucial. In this study, CFD-DEM (computational fluid dynamics-discrete element method) simulation method is employed to calculate various cases, considering five parameters: pipeline bending radius and angle, conveying velocity, particle diameter, and concentration, to explore the influence of these parameters on pressure drop and erosion rate of pipeline and result in a data set of hundreds of cases. Based on this data set, seven machine learning models are trained to predict pressure drop and erosion rate, respectively. To enhance model accuracy, the stacking method in ensemble learning is employed to combine multiple models with good performance. Additionally, the Optuna and SHAP (SHapley Additive exPlanation) methods are utilized to optimize hyperparameters and explain the degree to which parameters impact the predictions. The result demonstrates that pressure drop is almost unaffected by bending radius, while erosion rate initially decreases and then increases with bending angle, and both increase with other parameters. Among the evaluated models, artificial neural network, XGBoost, and random forest all demonstrate high prediction accuracy. The stacking model further improves the accuracy, with mean absolute error improving by 21.7% and 32.2%, and the SHAP method demonstrated good interpretability, which is basically consistent with CFD-DEM results.
Electronic excitation of high-order spoof surface plasmons on metallic grating at terahertz frequencies
Authors: Liu Yong-Qiang , Wang Yan , Sun Jinhai , Zhu Yong , Yin Hongcheng
Published: February 2024

High-order spoof surface plasmon (SSP) mode on corrugated metallic surfaces can find many interesting applications, such as in imaging, sensing, transmission and enhanced radiation source, etc. In this paper, an efficient excitation method of the high-order SSP mode by using an injected electron beam on the uniform rectangular metallic grating is proposed and investigated numerically. Based on the matched wave momentum between the SSP mode and the electron beam, both the fundamental and high-order SSP modes can be excited on the structure by using a single injected electron beam. Numerical simulation results indicate that the maximum electric field intensity of the generated high-order SSP mode is about two orders higher than that of the fundamental SSP mode. In addition, the peak power of the excited high-order SSP mode is almost two times that of the fundamental SSP mode power by the same energy electron beam, which demonstrates the obvious advantage of the high-order SSP electronic excitation approach compared to the previous fundamental SSP mode excitation on the structure. The central working frequency of high-order SSP power spectrum is about three times that of the fundamental SSP power spectrum. Moreover, the influences of the injected electron beam energy on the excited SSP power spectrum are analyzed specifically. It is shown that the generated SSP power spectrum demonstrates a blue shift with the decreased working voltage of the electron beam simultaneously, with its peak power increasing. However, the working bandwidth is narrowed with decreased beam voltage, which further reveals its working mechanism of presented electronic excitation of the SSP mode. The presented studies provide a new method to excite a high-order SSP mode on the metallic grating, which can find some potential applications in high-sensitivity sensing, deep sub-wavelength waveguide, and many others in terahertz spectra.
Three-dimensional numerical investigation of a suspension flow in an eccentric Couette flow geometry
Authors: Badia A. , D'Ambrosio E. , D'Angelo Y. , Peters F. , Lobry L.
Published: February 2024

This paper investigates the influence of eccentricity on flow characteristics and particle migration in Couette geometries. The study involves numerical simulations using the recent frame-invariant model developed by Badia et al. [J. Non-Newtonian Fluid Mech. 309, 104904 (2022)]. The study begins with a two-dimensional analysis, focusing first on the Newtonian fluid in order to thoroughly characterize the specific properties of this flow configuration. Next, the impact of eccentricity on particle migration in an isodense suspension is examined by numerical simulations based on the experiments conducted by Subia et al. [J. Fluid Mech. 373, 193–219 (1998)]. Furthermore, the study is extended to include a full three-dimensional analysis of a dense suspension flow in an eccentric Couette geometry based on resuspension experiments conducted by Saint-Michel et al. [Phys. Fluids 31, 103301 (2019)] and D'Ambrosio et al.[J. Fluid Mech. 911, A22 (2021)]. The main objective of the latter study is to investigate the influence of eccentricity on the resuspension height and on the calculation of the particle normal stress in the vertical direction through the volume fraction profile analysis. Our results show that even minimal eccentricity can lead to significant changes compared to the centered case.
Electron energy gain due to a laser frequency modulation experienced by electron during betatron motion
Authors: Arefiev A. , Yeh I.-L. , Tangtartharakul K. , Willingale L.
Published: February 2024

Direct laser acceleration of electrons is an important energy deposition mechanism for laser-irradiated plasmas that is particularly effective at relativistic laser intensities in the presence of quasi-static laser-driven plasma electric and magnetic fields. These radial electric and azimuthal magnetic fields provide transverse electron confinement by inducing betatron oscillations of forward-moving electrons undergoing laser acceleration. Electrons are said to experience a betatron resonance when the frequency of betatron oscillations matches the average frequency of the laser field oscillations at the electron position. In this paper, we show that the modulation of the laser frequency as seen by an electron performing betatron oscillations can be another important mechanism for net energy gain that is qualitatively different from the betatron resonance. Specifically, we show that the frequency modulation experienced by the electron can lead to net energy gain in the regime where the laser field performs three oscillations per betatron oscillation. There is no net energy gain in this regime without the modulation because the energy gain is fully compensated by the energy loss. The modulation slows down the laser oscillation near transverse stopping points, increasing the time interval during which the electron gains energy and making it possible to achieve net energy gain.
Synthetic Mirnov diagnostic for the validation of experimental observations
Authors: Büschel C. , Kleiber R. , Könies A. , Drevlak M. , Borchardt M. , Rahbarnia K. , Thomsen H. , Vaz Mendes S. , Brandt C. , Knauer J. , Brunner K. J. ,   Wendelstein 7-X Team
Published: February 2024

A synthetic Mirnov diagnostic has been developed to investigate the capabilities and limitations of an arrangement of Mirnov coils in terms of a mode analysis. Eight test cases have been developed, with different coil arrangements and magnetic field configurations. Three of those cases are experimental configurations of the stellarator Wendelstein 7-X. It is observed that, for a high triangularity of the flux surfaces, the arrangement of the coils plays a significant role in the exact determination of the poloidal mode number. For the mode analysis, torus and magnetic coordinates have been used. In most cases, the reconstruction of the poloidal mode number of a prescribed mode was found to be more accurate in magnetic coordinates. As an application, the signal of an Alfvén eigenmode, which has been calculated with a three-dimensional magnetohydrodynamics code, is compared to experimental observations at Wendelstein 7-X. For the chosen example, the calculated and measured mode spectra agree very well and additional information on the toroidal mode number and localization of the mode has been inferred.
Numerical investigation of the effects of intake pipe deflection angles on the in-cylinder flow and vortex structures of a cycloidal rotary engine
Authors: Zhu Hongzhang , Deng Xiwen , Xie Guangyi , Lin Xianyan , Lei Jilin , Jia Dewen
Published: February 2024

Intake pipe structure has a pivotal impact on the distribution of vortices within the combustion chamber in a cycloidal rotary engine (CRE). Therefore, studying the influence of the intake pipe deflection angle (IPDA) on the in-cylinder airflow motion has significant importance for enhancing CRE performance. This study utilized computational fluid dynamics and chemical reaction kinetics methods to establish a numerical simulation model for the in-cylinder flow and combustion in the CRE. Subsequently, the Omega vortex identification method was employed to investigate the influence of IPDA on the vortex structures within the cylinder and to explore the relationship between CRE performance and the vortices. The research findings indicate that although the IPDA did not significantly alter the fuel mass injected into the cylinder, it increased the airflow velocity by 14.6% during the main intake stage and increased the mass fraction of the burned fuel at the compression top dead center by 19.1%. Additionally, the increased airflow velocity within the cylinder led to improvements in both the mean tumble ratio by 186.5% and the turbulent kinetic energy by 25.5%. Furthermore, the IPDA significantly changed the distribution of vortices within the cylinder, which is a key factor contributing to the combustion variation of the CRE. The case of IPDA = 16° provided the largest volume of the strong vortices and the highest mean in-cylinder pressure. Compared to the original design, the volume of strong vortices was 1323.6% greater, and the mean in-cylinder pressure was higher by 5.3%.
Optical properties and exciton transfer between N-heterocyclic carbene iridium(III) complexes for blue light-emitting diode applications from first principles
Authors: Lebedeva Irina V. , Jornet-Somoza Joaquim
Published: February 2024

N-heterocyclic carbene (NHC) iridium(III) complexes are considered as promising candidates for blue emitters in organic light-emitting diodes. They can play the roles of the emitter as well as of electron and hole transporters in the same emission layer. We investigate optical transitions in such complexes with account of geometry and electronic structure changes upon excitation or charging and exciton transfer between the complexes from first principles. It is shown that excitation of NHC iridium complexes is accompanied by a large reorganization energy ∼0.7 eV and a significant loss in the oscillator strength, which should lead to low exciton diffusion. Calculations with account of spin–orbit coupling reveal a small singlet–triplet splitting ∼0.1 eV, whereas the oscillator strength for triplet excitations is found to be an order of magnitude smaller than for the singlet ones. The contributions of the Förster and Dexter mechanisms are analyzed via the explicit integration of transition densities. It is shown that for typical distances between emitter complexes in the emission layer, the contribution of the Dexter mechanism should be negligible compared to the Förster mechanism. At the same time, the ideal dipole approximation, although giving the correct order of the exciton coupling, fails to reproduce the result taking into account spatial distribution of the transition density. For charged NHC complexes, we find a number of optical transitions close to the emission peak of the blue emitter with high exciton transfer rates that can be responsible for exciton–polaron quenching. The nature of these transitions is analyzed.
Granular roll waves on a
μ
(J) rheology model: A dynamical systems perspective
Authors: Kanellopoulos Giorgos
Published: February 2024

This paper focuses on the formation and the unique characteristics of granular roll waves generated by utilizing the depth-averaged dynamic model recently introduced by Fei et al. [Appl. Math. Modell. 119, 763–781 (2023)], which employs μ(J) rheology. Notably, the symmetrical shape of the generated roll waves deviates from the typical pattern observed in both dry granular and water roll waves, which demonstrate a gradually rising flank followed by a sudden drop. Through a dynamical systems analysis and the associated phase space diagrams, which provide a comprehensive geometrical overview, we reveal the mathematical properties associated with the stable-uniform flow and the emergence of the granular roll waves. We then delve into the correlation between the shape of these roll waves and the nullclines of the dynamical system, whose analytical expression is presented. Additionally, we highlight the qualitative similarities and differences between the aforementioned model for liquid-immersed flowing granular matter and its well-established counterpart for dry granular flows based on the μ(I) rheology.