bluuebunny/crossref_metadata_2025 huggingface dataset:
Approach for identifying crop seeds with similar appearances using hyperspectral images and improved ResNet 18 based on cloud platform
Authors: Li Hui , Duan Xuliang
Published: December 2024

This study proposes an improved ResNet18 model based on cloud platform and hyperspectral image to identify crop seeds. Hyperspectral images are preprocessed by moving average method (MA) and standard normal variable transformation (SNV) to reduce spectral data interference. The successive projection algorithm (SPA) is used to select characteristic wavelengths and reduce the band dimension. The heterogeneous convolution and channel attention mechanism (CAM) are used to reduce parameters and computation load of ResNet18. Image recognition with improved ResNet18 takes 4.4 s with 4.2 s improvement over the original ResNet18 and saves 2808 KB memory. Accuracy has increased from 93.1% to 96.7%. The improved ResNet18 was deployed on Alibaba Cloud ESC server with uWSGI, Nginx and flask to achieve high concurrency and fast recognition. For single‐variety seed identification, the average time reduced to 0.56 s, with an 87% decrease and accuracy is 96.3%. For mixed seeds of five types, accuracy is 90.22% with a time consumption of 0.88 s. The results demonstrated that the proposed method exhibited high effectiveness and accuracy.
Few‐shot real scenes convolutional anchor clustering twin network for hyperspectral image classification
Authors: Zhou Xiangshan , Tong Xiaoyi , Zhou Xuchuan , Wang Lin , Zhang Lei , Zhou Jie , Qin Su
Published: December 2024

In order to improve the performance of hyperspectral open set recognition processing with insufficient sample size, the authors propose a new supervised contrastive learning (SCL) framework (FSSCL‐OSC) that can achieve open‐set classification of hyperspectral images in scenarios with very few sample sizes, which consists of three steps. First, supervised contrastive learning (SCL) with geometric transformations is designed, which uses rotated labels as supervision to obtain lower‐level characteristics that more accurately capture various orientations and then makes use of a spectral‐spatial characteristic extraction network to maximize the utilization of HSI's spectrum and spatial information. Next, a class anchor open‐set classification module based on a twin clustering network is designed, which uses SCL and FSL to extract more specific personal information by mining the category‐invariant characteristics present in the known versus unknown class data. Finally, multiple convolution and open‐set recognition (OSC) is performed on the feature blocks. Experimental results on three classical HSI datasets show that FSSCL‐OSC provides a significant improvement over existing methods, under a sample size of only 10%, the overall accuracy reached 82.38%, 90.76% and 84.70%, respectively.
The long‐term influence of wind and temperature on performance and degradation within an utility‐scale photovoltaic plant
Authors: Daniel‐Durandt Francisca Muriel , Rix Arnold Johan
Published: December 2024

An inverter‐level analysis of a large photovoltaic (PV) plant is evaluated over four years to investigate the long‐term performance and degradation caused by wind and temperature effects. The multi‐megawatt utility‐scale PV plant is located in a semi‐arid region in South Africa. The degradation rate is determined using the performance ratio as a comparison metric between the different inverters. The degradation from the first year of operation up to the fourth year shows that different areas of the PV plant have varying degradation rates. The spatial degradation analysis indicates that inverter blocks operating at higher ambient temperatures and lower wind frequency measurements show higher rates of degradation compared to inverter groups operating at lower temperatures and higher wind frequency. Notably, the lowest degradation rates correlate positively with wind direction and frequency from the North and North‐East, indicative of a cooling influence on the PV modules. The weather‐corrected performance analysis indicates that the most prominent wind direction (North) has the highest mean performance ratio, further supporting the claims that the cooling effect of wind improves performance and efficiency. The widening gap between the best‐ and worst‐performing inverters annually underscores the premise that specific inverters' PV modules degrade at disparate rates within the PV plant. The results of this work present future designs of PV plants that could potentially be optimised to take advantage of wind as a cooling tool, which may further enhance the longevity and sustainability of large PV installations.
Detection of stellar wakes in the Milky Way: A deep learning approach
Authors: Põder Sven , Pata Joosep , Benito María , Alonso Asensio Isaac , Dalla Vecchia Claudio
Published: December 2024

Context. Due to poor observational constraints on the low-mass end of the subhalo mass function, the detection of dark matter (DM) subhalos on sub-galactic scales would provide valuable information about the nature of DM. Stellar wakes, induced by passing DM subhalos, encode information about the mass (properties) of the inducing perturber and thus serve as an indirect probe for the DM substructure within the Milky Way.

Aims. Our aim is to assess the viability and performance of deep learning searches for stellar wakes in the Galactic stellar halo caused by DM subhalos of varying mass.

Methods. We simulated massive objects (subhalos) moving through a homogeneous medium of DM and star particles with phase-space parameters tailored to replicate the conditions of the Galaxy at a specific distance from the Galactic centre. The simulation data was used to train deep neural networks with the purpose of inferring both the presence and mass of the moving perturber. We then investigated the performance of our deep learning models and identified the limitations of our current approach.

Results. We present an approach that allows for quantitative assessment of subhalo detectability in varying conditions of the Galactic stellar and DM halos. We find that our binary classifier is able to infer the presence of subhalos in our generated mock datasets, showing non-trivial performance down to a mass of 5 × 107 M⊙. In a multiple-hypothesis case, we are also able to discern between samples containing subhalos of different mass. By simulating datasets describing subhalo orbits at different Galactocentric distances, we tested the robustness of our binary classification model and found that it performs well with data generated from different initial physical conditions. Based on the phase-space observables available to us, we conclude that overdensity and velocity divergence are the most important features for subhalo detection performance.
Interaction between the supernova remnant W44 and the infrared dark cloud G034.77-00.55: Shock induced star formation
Authors: Cosentino G. , Jiménez-Serra I. , Barnes A. T. , Tan J. C. , Fontani F. , Caselli P. , Henshaw J. D. , Law C.-Y. , Viti S. , Fedriani R. , Hsu C.-J. , Gorai P. , Zeng S. , De Simone M.
Published: December 2024

Context. We have studied the dense gas morphology and kinematics towards the infrared dark cloud (IRDC) G034.77-00.55, shock-interacting with the SNR W44, to identify evidence of early-stage star formation induced by the shock.

Aims. We used high angular resolution N2H+(1−0) images across G034.77-00.55, obtained with the Atacama Large Millimeter/sub-Millimeter Array. N2H+ is a well-known tracer of dense and cold material, optimal for identifying gas that has the highest potential to harbour star formation.

Methods. The N2H+ emission is distributed in two elongated structures, one towards the dense ridge at the edge of the source and one towards the inner cloud. Both elongations are spatially associated with well-defined mass-surface density features. The velocities of the gas in the two structures (i.e. 38–41 km s−1 and 41–43 km s−1) are consistent with the lowest velocities of the J- and C-type parts, respectively, of the SNR-driven shock. A third velocity component is present at 43–45.5 km s–1. The dense gas shows a fragmented morphology with core-like fragments at scales consistent with the Jeans lengths, masses of ~1–20 M⊙, densities of (n(H2)≥105 cm–3) sufficient to host star formation in free-fall timescales (a few 104 yr), and with virial parameters that suggest a possible collapse.

Results. The W44 driven shock may have swept up the encountered material, which is now seen as a dense ridge, almost detached from the main cloud, and an elongation within the inner cloud, well constrained in both N2H+ emission and mass surface density. This shock compressed material may have then fragmented into cores that are either in a starless or pre-stellar stage. Additional observations are needed to confirm this scenario and the nature of the cores.
Gaia vbroad: Spectral-line broadening and binarity
Authors: Hadad E. , Mazeh T. , Faigler S. , Brown A. G. A.
Published: December 2024

The Gaia DR3 catalogue includes line-broadening measurements (vbroad) for 3 524 677 stars. We concentrate here on the low-mass main-sequence (MS) sub-sample of the catalogue, with (GBP − GRP)0 in the range of 1–1.6, which includes 81 371 sources. The colour-magnitude diagram of the sample displays two distinct strips, the brighter of which is probably mostly composed of unresolved binaries, with mass ratios close to unity. We show that the suspected binary sub-sample displays a larger vbroad distribution, which we attribute to the unresolved absorption lines of the two components of each binary. A similar effect is seen in the GALAH data.
Stabilization of control systems associated with a strongly continuous group
Authors: Nguyen Hoai-Minh
Published: December 2024

This paper is devoted to the stabilization of a linear control system $y' = A y + B u$  and its suitable non-linear variants where $(A, \cD(A))$ is an infinitesimal generator of a strongly continuous {\it group} in a Hilbert space $\mH$, and $B$ defined in a Hilbert space $\mU$ is an admissible control operator with respect to the semigroup generated by $A$. Let $\lambda  \in \mR$ and assume that, for some {\it positive} symmetric, invertible  $Q = Q(\lambda) \in \cL(\mH)$,  for some {\it non-negative}, symmetric  $R = R(\lambda) \in \cL(\mH)$, and for some {\it non-negative}, symmetric $W = W(\lambda) \in \cL(\mU)$,  it holds 
[[EQUATION]] 
We then present a new approach to study the stabilization of such a system and its suitable nonlinear variants. Both the stabilization using dynamic feedback controls and the stabilization using static feedback controls in a weak sense are investigated. To our knowledge, the nonlinear case is out of reach previously when $B$ is unbounded for both types of stabilization.
Detailed Analysis of Fetal Malformations of the Supratentorial
Structures of the Brain in High-Risk Pregnancies at 12–14 Gestational Weeks by
Transvaginal 3D Ultrasound Examination
Authors: Altmann Reinhard , Scharnreitner Iris , Enengl Sabine , Stelzl Patrick , Oppelt Peter , Reiter Elisabeth
Published: December 2024

Purpose  To detect sonographic abnormalities of the supratentorial
structures of the brain – future cavum septum pellucidum, cavum velum
interpositum, third ventricle, ganglionic eminence and thalamus/hypothalamus –
in fetuses with a crown-rump length of 45–84 mm in high-risk pregnancies.

Materials and Methods  This study presents the retrospective analysis of
transvaginally recorded 3D volumes of the fetal brain of 64 fetuses whose
mothers consulted our ambulatory department for fetomaternal medicine for
organic and/or genetic changes of their fetuses at GW 12–14. For this study we
selected fetuses with 3D volume blocks of the fetal brain at best sonographic
quality enabling detailed analysis and measurement of the supratentorial brain
structures to correlate the results with the results of genetic analysis,
ultrasound controls in later weeks of pregnancy, and fetal outcome.

Results  Of 44 fetuses with genetic changes and 20 fetuses with syndromic
changes, structural brain changes were found in 27 fetuses, analyzed by
correlating the brain structures with the recently published structures of the
brain at gestational week 12-14 in early pregnancy, presenting new details of
early pathological brain development – migration disorders, milder variants of
holoprosencephaly (lobar, MIH), corpus callosum agenesis, for the first time in
early pregnancy.

Conclusion  Supratentorial defects of the brain can be detected and
analyzed in GW 12–14 in detail by direct analysis of sonopathology and
visualization of pathological measurements using transvaginal 3D sonography in
high quality.
SGLT-2-Inhibitoren – Eine Standortbestimmung in der deutschen oralen Therapielandschaft für Menschen mit Typ-2-Diabetes
Authors: Aberle Jens , Blüher Matthias , Laudes Matthias , Merkel Martin , Sandow Petra
Published: December 2024

Wie aus zahlreichen umfangreichen Studien hervorgeht, haben SGLT-2-Inhibitoren nicht nur positive Effekte auf den Glukosestoffwechsel, sondern darüber hinaus eine ausgeprägte protektive Wirkung auf Herz und Nieren. Damit kommt dieser Wirkstoffklasse eine wichtige Rolle in der Primär- und Sekundärprävention diabetes-assoziierter Komorbiditäten zu. Leitlinien sprechen auf Basis der Evidenz für SGLT-2-Inhibitoren eine Empfehlung für deren frühen Einsatz bei Menschen mit Typ-2-Diabetes und gleichzeitigem hohen Risiko für kardiovaskuläre und/oder renale Ereignisse aus. Verordnungszahlen zeigen jedoch, dass diese Empfehlungen aktuell nicht umgesetzt werden und deutlich mehr Menschen mit Typ-2-Diabetes von einer organprotektiven Therapie profitieren könnten. Daher soll in dieser Übersichtsarbeit der Stellenwert der SGLT-2-Inhibitoren im Vergleich zu anderen oralen Therapieansätzen für die Behandlung des Typ-2-Diabetes dargestellt werden.
Die Wegbereiter Schwerin und Brandenburg-Görden bei der Entwicklung
der Therapie von Alkoholkonsumstörungen in der DDR
Authors: Pontzen Nadja , Steinberg Holger
Published: December 2024

Ziele der Studie Die Studie gewährt Einblicke in die suchttherapeutischen
Konzepte der Kliniken von Hugo von Keyserlingk in Schwerin und Hubertus
Windischmann in Brandenburg und ermöglicht ein Verständnis der spezifischen
Problemlagen in diesem Teilbereich der psychiatrischen Versorgung in der DDR.

Methodik Vornehmlich in der DDR selbst publizierte Arbeiten werden
eruiert, analysiert und kontextualisiert. Die Experteninterviews mit zwei
führenden Suchttherapeuten der DDR, von Keyserlingk und Windischmann, ergänzen
und vertiefen die schriftlichen Quellen.

Ergebnisse Anfänglich noch mangelhafte Ansätze zur Alkoholkrankentherapie
nach dem Zweiten Weltkrieg entwickelten sich allmählich zu komplexeren und auch
verschiedenartigen Strukturen. So entstand ab den 1960er-Jahren unter von
Keyserlingk eine Suchtklinik, während Windischmann ein Suchtkrankendispensaire
mit verschiedenen Therapieoptionen etablierte.

Schlussfolgerungen Die Beiträge von Keyserlingks und Windischmanns spielen
eine bedeutende Rolle bei der Entwicklung von Therapiekonzepten. Es wird durch
die Studie deutlich, dass sie für die Alkoholkrankenfürsorge in der DDR
Pionierfunktion hatten.
Selective Bilateral Posterior Canal Dysfunction: A Case Series Investigation into the Clinical Trends and Associative Factors
Authors: Behr Evalena R. , Honaker Julie A.
Published: December 2024

Background The video head impulse test measures high-frequency vestibulo-ocular function of all six semicircular canals. Isolated semicircular canal dysfunction has been correlated with several peripheral and central vestibular etiologies. Selective bilateral posterior canal dysfunction is a trend seen in the clinical setting but less commonly reported in the medical literature.

Purpose The purpose of this work is to explore the clinical profile of bilateral posterior canal dysfunction along with other presenting factors such as hearing loss, increased age, and associated nystagmus patterns.

Method A case series of three patients (age range: 67–74 years) is presented to illustrate the similarities and clinical associations between vestibular and balance history, medical history, and vestibular test results.

Results All three patient cases presented with below reference range posterior semicircular canal function on video head impulse testing. Two patients also presented with down-beating nystagmus, and two endorsed subjective hearing loss while the third presented with presbycusis.

Conclusion Selective bilateral posterior canal dysfunction in association with advanced age, presbycusis, and signs of down-beating nystagmus may be associated with vestibulocochlear degenerative processes. Yet, central disorders, technical and patient factors may present clinical challenges to elucidate the cause.
School-Based Professionals' Knowledge of Autistic Speech and Augmentative and Alternative Communication Decision Making
Authors: Zisk Alyssa Hillary , Eddy Brandon , Donaldson Amy L. , Cannalonga Sara , Strickland Olivia , corbin endever , schall jorja harper t
Published: December 2024

Autistic adults report communication access barriers related to the prioritization of speech over all other forms of communication. Our participatory research team, including autistic adults who use augmentative and alternative communication (AAC) both part- and full-time, designed and administered a 35-question online survey to examine school-based professionals' knowledge, training, and practices related to AAC and autism. The current study reports a portion of the larger data set specific to participants' definitions of speech terms related to autistic speech. A total of 567 participants completed the survey. Thematic analysis of participants' responses to speech definitions revealed multiple themes, including a focus on speech without implying or suggesting other forms of communication, speech production (mechanics), communication functions (intentionality), deficits, and definitions that were exclusionary in nature (e.g., identifying what the term did not define). Quantitative analysis of definitions of autistic speech revealed the need for increased exposure to these internal speech states for professionals working with autistic children. Increasing school-based professionals' knowledge, including community-sourced knowledge, related to autism and AAC, can improve access to AAC for speaking autistic students who may benefit from AAC.
Enigma of Gastric Teratoma in Infants: A Case Series
Authors: Saha Soumitra , Tripathi Mayank , Vineet Kumar , Kale Ajinkya , Pande Pooja , Chowdhury Zachariah , Ranjan Raghwesh
Published: December 2024

Gastric teratomas are an extremely rare variety of teratomas in children. The aim of our series is to present the natural history and progression of the disease. Retrospective analysis of prospectively maintained data of all the gastric teratoma patients treated at our center was done from their electronic medical records. A total of four cases of gastric teratoma were found to have been treated, all of them being less than 1 year old with three-fourths being male. Typical imaging features of teratoma along with normal germ cell tumor markers helped in making a diagnosis. Surgery is the main form of treatment. In final histopathology, there was equal distribution of mature and immature teratomas. On long-term follow-up, there has been no incidence of recurrence. There needs to be reporting of more cases to verify its natural history.
Phase equilibrium curve of an antiferromagnet with strong crystal field anisotropy
Authors: Prystasz V.
Published: December 2024

The equilibrium curve is found for the ferromagnetic and tilted phases for the case of high values of the crystal field anisotropy constants of a two-sublattice antiferromagnet (metamagnet).
Impact of laser energy density on engineering resistive switching dynamics in self-rectifying analog memristors based on BiFeO3 thin films
Authors: Zhao Xianyue , Li Kefeng , Chen Ziang , Dellith Jan , Dellith Andrea , Diegel Marco , Blaschke Daniel , Menzel Stephan , Polian Ilia , Schmidt Heidemarie , Du Nan
Published: December 2024

This study explores the feasibility of precisely tuning the resistive switching behavior of Au/BiFeO3/Pt/Ti/SiO2/Si memristors through controlled modulation of laser energy density during pulsed laser deposition (PLD). By systematically reducing the laser energy density within the fabrication process, notable alterations in the properties of the BiFeO3 (BFO) thin film are observed. As the laser energy density decreases, the grain size in the BFO film and the thickness of the film decrease. Furthermore, we obtain the minute structural variations in response to the diverse laser energy densities employed during the deposition process. Energy-dispersive x-ray spectroscopy analysis is employed to investigate the distribution of Ti4+ ions within the BFO thin film. The reduction in the grain size and film thickness, along with the prominent nucleation of specifically oriented grains, and the diffusion of Ti4+ ions, lead to the BFO memristor fabricated with a lower laser energy density having more grain boundaries and a shortened conduction path (grain boundary) in the thickness direction. Consequently, the enhanced movement of oxygen vacancies facilitates their preferential accumulation along the grain boundaries within the BFO layer, resulting in an augmented on/off ratio, rectification factor, and set current in the devices. Overall, our findings explain the significant influence of laser energy density in PLD on the microstructure and electrical properties of BFO thin films. Particularly, the lower energy densities are employed to improve electrical characteristics. This research not only enhances our fundamental understanding but also provides valuable insights into optimizing BFO memristors for reliable, robust, and practical applications.
Phase transitions in the Co-doped Heusler alloy Ni2Mn1−xCoxGa
Authors: Chen Jing-Han , Poudel Chhetri Tej , Wrobel Nathaniel , Bai Xiaojian , Young David P. , Dubenko Igor , Talapatra Saikat , Ali Naushad , Stadler Shane
Published: December 2024

The phase transitions of a series of Co-doped Heusler alloys, Ni2Mn1−xCoxGa (0⩽x⩽0.2), were investigated experimentally using the magnetization measurements, x-ray diffraction, and calorimetric measurements up to their respective melting points. With increasing Co concentration, the structural transition temperatures, Curie temperatures, and melting points, were observed to increase, while the order–disorder transition temperatures decreased. Temperature-dependent x-ray diffraction experiments revealed two different crystal structures in the low-temperature martensite phase for different Co concentrations. However, above their respective structural transitions, both low-temperature crystal structures transformed into the L21 cubic structure. These findings enabled the construction of a complete magnetic and structural phase diagram for Ni2Mn1−xCoxGa, spanning from cryogenic temperatures to the melting points. The temperature-dependent XRD results revealed the abrupt changes in interatomic Mn–Mn distances, which validates the crucial role of Mn–Mn interatomic distance and the effect of the magnetic coupling competition in the structural stability between the martensite phase and austenite phase.
A coaxial solid state nonlinear pulse forming line with an exponentially tapered ferrite composite core
Authors: Crawford Travis D. , Evers Sophia I. , Sapoff Bradley H. , Garner Allen L.
Published: December 2024

The need to optimize size, weight, and power of high-power microwave (HPM) systems has motivated the development of solid-state HPM sources, such as nonlinear transmission lines (NLTLs), which utilize gyromagnetic precession or dispersion to generate RF. One recent development implemented the NLTL as a pulse forming line (PFL) to form a nonlinear pulse forming line (NPFL) system that substantially reduced the system’s size by eliminating the need for a separate PFL; however, matching standard loads can be challenging. This paper describes the development of a tapered NPFL using an exponentially tapered composite based ferrite core containing 60% nickel zinc ferrite (by volume) encased in polydimethylsiloxane (PDMS) and encapsulated in a 5% barium strontium titanate shell. The tapers exponentially change the line’s impedance from a 50 Ω standard HN connection to 25 Ω before tapering back to 50 Ω. We characterized the core behavior by obtaining magnetization curves and ferromagnetic resonance measurements. The rise time (10%–90%) of the pulse decreased from ∼6 ns for 5 kV charging voltage to 1.8 ns for 15 kV charging voltage. Under unbiased conditions, the system generated HPM with a center frequency of ∼850 MHz with a 3 dB bandwidth of 125 MHz. Magnetic biases of 15 and 25 kA/m increased the modulation depth and decreased the center frequency to ∼500 MHz for 15 kV charging voltage.
Nature of the carrier dynamics and contrast formation on the photoactive material surfaces: Insight from ultrafast imaging to DFT calculations
Authors: Nematulloev Sarvarkhodzha , Nughays Razan O. , Nematulloev Saidkhodzha , Thomas Simil , Naphade Dipti R. , Anthopoulos Thomas , Bakr Osman M. , Alshareef Husam N. , Mohammed Omar F.
Published: December 2024

Precise material design and surface engineering play a crucial role in enhancing the performance of optoelectronic devices. These efforts are undertaken to particularly control the optoelectronic properties and regulate charge carrier dynamics at the surface and interface. In this study, we used ultrafast scanning electron microscopy (USEM), which is a powerful and highly sensitive surface tool that provides unique information about the photoactive charge dynamics of material surfaces selectively and spontaneously in real time and space in high spatial and temporal resolution. Here, time-resolved images of CdTe (110), CdSe (100), GaAs (110), and other semiconductors revealed that the presence of oxide layers on the surface of materials leads to an increase in the work function (WF) and trap state densities upon optical excitation, leading to the formation of dark image contrast in USEM experiments. These findings were further supported by ab initio calculations, which confirmed the reliability of the observed changes in the excited surface WFs. Besides enhancing our understanding of surface charge dynamics, it also offers valuable insights into manipulating these properties. This study paves the way for precise control and the potential to design highly efficient light-harvesting devices.
Predicting viscosities and thermal conductivities from dilute gas to dense liquid: Deriving fundamental transfer lengths for momentum and energy exchange in revised Enskog theory
Authors: Jervell Vegard G. , Wilhelmsen Øivind
Published: December 2024

Chapman–Enskog theory has long provided an accurate description of the transport properties of dilute gas mixtures. At elevated densities, revised Enskog theory (RET) provides a framework for describing the departure of the transport properties from their dilute-gas values. Various methods of adapting RET for the description of real fluids have been proposed in the literature. The methods have in common that they incorporate one or more length scales to describe molecular interactions. With few exceptions, the required length scales have been estimated from experimental transport property data. In this work, we introduce two transfer lengths that describe the residual transport of momentum and energy. We derive a model called the exchange-weighted closest approach (EWCA), which links the transfer lengths to the intermolecular potential. Combining the EWCA model with Mie potentials fitted to experimental equilibrium properties yields accurate predictions for several real fluids, including a binary mixture. At higher temperatures, the theory is accurate at surprisingly high densities, even up to the liquid–solid transition of argon. We demonstrate how the transfer lengths can be computed from experimental data or correlations for the transport properties. The transfer lengths obtained in this manner are in good agreement with those obtained from the EWCA model paired with an accurate ab initio potential for argon. The results suggest that kinetic theory, after further developments, can become a predictive theory also for liquids.
Beyond the Debye–Hückel limit: Toward a general theory for concentrated electrolytes
Authors: Dinpajooh Mohammadhasan , Intan Nadia N. , Duignan Timothy T. , Biasin Elisa , Fulton John L. , Kathmann Shawn M. , Schenter Gregory K. , Mundy Christopher J.
Published: December 2024

The phenomenon of underscreening in concentrated electrolyte solutions leads to a larger decay length of the charge–charge correlation than the prediction of Debye–Hückel (DH) theory and has found a resurgence of both theoretical and experimental interest in the chemical physics community. To systematically understand and investigate this phenomenon in electrolytes requires a theory of concentrated electrolytes to describe charge–charge correlations beyond the DH theory. We review the theories of electrolytes that can transition from the DH limit to concentrations where charge correlations dominate, giving rise to underscreening and the associated Kirkwood Transitions (KTs). In this perspective, we provide a conceptual approach to a theoretical formulation of electrolyte solutions that exploits the competition between molecular-informed short-range (SR) and long-range interactions. We demonstrate that all deviations from the DH limit for real electrolyte solutions can be expressed through a single function ΣQ that can be determined both theoretically and numerically. Importantly, ΣQ can be directly related to the details of SR interactions and, therefore, can be used as a tool to understand how differences in representations of interaction can influence collective effects. The precise function form of ΣQ can be inferred through a Gaussian field theory of both the number and charge densities. The resulting formulation is validated by experiment and can accurately describe the collective phenomenon of screening in concentrated bulk electrolytes. Importantly, the Gaussian field theory predictions of the screening lengths appear to be less than ∼1 nm at concentrations above KTs.
Flexible and broadband microwave-absorbing metastructure with wide-angle stability
Authors: Lin Feihong , Bai Yu , Chen Jiawei , Yan Zhongming , Zhou Hongcheng , Wang Yu
Published: December 2024

Flexible and broadband microwave-absorbing structures have attracted significant attention in electromagnetic (EM) science. Although previous studies have demonstrated the potential of flexible microwave-absorbing structures using thin dielectric substrates or flexible materials, the need for broadband and flexible microwave-absorbing structures remains largely unmet, especially those that can be stretched to adapt to complex surfaces. In this article, a novel design concept of a stretchable meta-substrate comprising rigid pyramidal substrates and soft hinges is proposed, which operates as a dielectric substrate and a structural support for the metastructure. The proposed flexible and broadband microwave-absorbing metastructure is composed of a pyramidal microwave-absorbing unit and a stretchable meta-substrate, which exhibits a reflection coefficient lower than −20 dB from 2.2 to 20 GHz under normal incidence. By overcoming the mechanical and electromagnetic limitations of previous efforts with a soft material-based microwave-absorbing structure, the proposed metastructure can be stretched under 40% strain, while the −10 dB reflection coefficient spectrum only shifts by 1.1 GHz. Furthermore, the proposed metastructure exhibits stable absorption properties for EM wave irradiation with both transverse electric and transverse magnetic polarizations, even at an oblique incident angle of up to 70°. As a proof of concept, the proposed metastructure is conformally pasted on the unmanned aerial vehicle surface, and the maximum radar cross section reduction of the proposed metastructure is 30.5 dB larger than that of a conventional device. The fabricated sample can be readily applied for carrying and deployment, with potential applications in the fields of EM stealth as well as EM anti-interference.
Systematic ab initio calculation of spectroscopic constants for A-reduced rotational effective Hamiltonians of asymmetric top molecules using normal ordering of cylindrical angular momentum operators
Authors: Krasnoshchekov Sergey V. , Efremov Ilya M. , Polyakov Igor V. , Millionshchikov Dmitry V.
Published: December 2024

This research paper presents a new fundamental approach for evaluating accurate ab initio quartic, sextic, and octic centrifugal distortion parameters of A-reduced rotational effective Hamiltonians of asymmetric top molecules. In this framework, the original Watson Hamiltonian, expanded up to sextic terms of kinetic and potential energies, is subjected to a series of vibrational and rotational operator unitary transformations, leading to reduced Watson effective Hamiltonians for the equilibrium configuration, ground state, and weakly perturbed vibrationally excited states. The proposed scheme is based on a numerical-analytic implementation of the sixth-order Van Vleck operator perturbation theory with the systematic normal ordering of vibrational rising and lowering operators (a†, a) and cylindrical angular momentum operators (Jz, J+, J−). The efficiency of the developed theoretical model is demonstrated by the juxtaposition of predicted centrifugal distortion parameters for several three to eight atomic molecules, including H2S, CH2O, C2H4, CH2D2, CH2F2, CH2Cl2, and B2H6, using the coupled-cluster single double triple/quadruple-ζ level of quantum chemistry. In comparison with the values derived using the customary analytic expressions, the calculated quartic and sextic parameters may improve by an order of magnitude in the fourth and sixth orders, respectively, reaching an accuracy of about 1%. Predicted octic constants can serve as an excellent starting point for fitting to experimental spectra.
Water permeation through single sub-micron pores in single layer graphene measured by a micro-particle image velocimetry technique
Authors: Gómez Samuel F. D. J. , Boutilier Michael S. H.
Published: December 2024

Graphene holds potential as a high permeance membrane material for separation applications owing to its single atom thickness. Transport rates through graphene pores ultimately determine membrane performance and are an area of focus of design efforts. In this regard, single pore flow rate measurements are desirable because they are not influenced by material defects present in large-area samples and are unaffected by modeling assumptions used in simulations. However, measuring liquid flow rates through single graphene pores is challenging. In this paper, we establish a micro-particle image velocimetry technique to measure flow rates through single pores or small permeable areas by comparing the velocity decay rate downstream of the pore to analytical predictions for the flow field. The method is validated on silicon nitride micropores by comparison with microfluidic sensor measurements and then applied to measure water permeation rates through single sub-micron graphene pores, below the detection limit of the sensor. A 200 nm diameter pore is measured to have a pore permeation coefficient of 1.5×10−19 m3 s−1 Pa−1, and 500 nm pores are measured to have pore permeation coefficients of 7.0×10−19 and 14×10−19 m3 s−1 Pa−1. These values are less than half those predicted by continuum theory, but of the same order of magnitude. The results provide measured permeances of experimentally realized flows through single sub-micron graphene pores and a reliable technique for measuring the liquid permeance of micrometer-scale membrane areas.
Viscous dissipation impacts on a developing thermal field in a saturated porous medium: An effective thermal management
Authors: Gupta Nitish , Bhargavi D. , Vajravelu Kuppalapalle
Published: December 2024

In this study, we investigate the impacts of two viscous dissipation models—the form drag (FD) model and the clear fluid compatible (CFC) model—on the thermal behavior of fluid flow within a porous medium in a parallel plate channel. We analyze temperature distributions under constant heat flux conditions by employing the local thermal non-equilibrium model and assuming unidirectional flow governed by the Darcy–Brinkman model. Our results indicate that an increase in the Brinkman number, Biot number, and thermal conductivity ratio enhances the temperature distribution. Notably, the CFC model demonstrates a higher local Nusselt number compared to that in the FD model, highlighting its potential for applications in heat exchanger design where efficient heat transfer is crucial. Our analysis aids in predicting thermal performance and efficiency, emphasizing the importance of selecting appropriate viscous dissipation models to achieve optimal thermal outcomes. The findings have significant applications in thermal management technologies. A comparative analysis with experimental and computational studies further strengthens these insights, making them applicable to a wide range of thermal systems (see Sec. V B). This study can assist engineers in accounting for viscous dissipation when designing systems that involve fluid flow through porous media, such as heat exchanger devices, particularly in the entrance region of ducts, where the thermal field begins to develop.
Cavity-enhanced dual-comb spectroscopy stabilized by molecular absorption line locking
Authors: Sun Haojia , Hu Mai , Nie Qinxue , Wang Zhen , Wei Chao , Ren Wei
Published: December 2024

We demonstrate an actively stabilized cavity-enhanced dual-comb spectroscopy to improve comb transmission through a high-finesse optical cavity. In this dual-comb spectroscopic method, one comb is phase-locked to a 34 cm cavity with a finesse of about 15 700, which is stabilized to the molecular absorption line. With this actively stabilized scheme, all comb lines can be locked to the center of the corresponding cavity mode. Comparison experiments are conducted to demonstrate the necessity of the proposed actively stabilized scheme for robust comb-cavity coupling under external disturbances. We achieved a signal-to-noise ratio of 114.5 with an averaging time of 9 ms for a spectral range of 4.5 cm−1, contributing to the intensity absorption coefficient of 5.14 × 10−8 cm−1 and the noise-equivalent absorption per spectral element of 3.08 × 10−10 cm−1Hz−1/2.
Coupled zone-adaptive turbulence and combustion modeling of turbulent swirling premixed flames
Authors: Chen Yuxuan , Yang Tianwei , Zhou Hua , Mo Yi , Chen Fan , Ren Zhuyin
Published: December 2024

Adaptivity has emerged as a crucial element for capturing the multi-scale dynamics and, therefore, effective turbulent flame simulations. This study explores the theoretical framework of the coupled adaptive turbulence and combustion modeling, in which self-adaptive turbulence eddy simulation (SATES) has been coupled with the zone-adaptive combustion model, the latter one dynamically assigns the laminar finite rate (LFR) model, and the particle-based transported probability density function (TPDF) method. A new length scale, LHybrid, was introduced for the Damköhler (Da) number calculation to ensure consistency between Reynolds-averaged Navier–Stokes and large eddy simulation modes within the SATES framework. The model performance is validated in the swirling burner technical flames (TECFLAM), which produces turbulent premixed flames with intense unsteadiness. The results show that the coupled adaptive simulation accurately reproduces the weak “M” shape flame, demonstrating reliable estimates of turbulence–chemistry interactions in the outer mixing layer. In contrast, the LFR simulation yields a strong M shape flame due to overestimated reaction rates. Quantitatively, both adaptive combustion model and TPDF methods yield a weak bimodal temperature profile and a constant equivalence ratio in the inner recirculation zone, aligning well with experimental data, while LFR overpredicts temperatures, leading to discrepancies in equivalence ratio and species mass fraction. The adaptive combustion model uses only 4.24% of the computational particles needed for TPDF, covering just 0.86% of the total domain, significantly reducing computational cost. Additionally, the new Da-number partitioning criteria based on LHybrid accurately identify regions of strong turbulence–chemistry interaction. It is shown that the adaptive method can converge to the corresponding LFR or TPDF model by adjusting the partitioning criterion parameter, illustrating its potential in balancing computational cost and prediction accuracy in turbulent flames.
Transformer based deep learning accelerated numerical simulation for incompressible flow
Authors: Cui Qingjie , Zhang Meina , Xiao Min , Ni Guoxi
Published: December 2024

Numerical simulation of fluid plays an important role in the research of engineering, weather, and climate; the classical methods solve incompressible Navier–Stokes equations, providing the most detailed flow information in many cases. However, an increase in the number of grids causes the computing cost to increase significantly. In this paper, we propose a deep learning-based numerical solver for incompressible flow to improve the accuracy of numerical simulation on coarse-resolution grids. The solver uses the Swin Transformer—a hierarchical vision transformer using shifted windows—to build independent subnetworks and learn the interpolating coefficients for the variable values on the cell edge and, thus, to obtain fluxes in different directions. Numerical experiments show that our proposed solver can perform better than the traditional numerical scheme, predicting the solution well and maintaining long-term computational stability.
Large-eddy simulation of an ejector integrated in a rotating detonation engine cycle
Authors: Uhl G. , Taileb S. , Odier N. , Poinsot T. , Bellenoue M.
Published: December 2024

To facilitate the integration of a rotating detonation combustor (RDC) in a turbomachine, adding an ejector downstream of the combustor may be a viable option. The present work examines the performance of an ejector configuration under unsteady inflow conditions representative of an RDC exhaust, using a Large-Eddy Simulation. The RDC exhaust gas is generated at the nozzle exit of the ejector by an adequate choice of inlet axial fluctuation amplitude and frequency. The results along the jet centerline showed that the ejector flow remains in the low supersonic regime before passing through a secondary shock located at the constant-area mixing chamber exit. Mixing between the two flows begins immediately at the confluence and terminates slightly upstream of the secondary shock. The consideration of a theoretical thermodynamic cycle with the calculated ejector revealed that the ejector presence increases specific fuel consumption with respect to a reference cycle without an ejector installed. Entropy generation analysis showed that losses associated with thermal conduction have the most significant impact, followed by viscous dissipation losses. Both originate primarily in the shear layer between the RDC exhaust and the secondary flow. The flow characteristics at the ejector outlet and turbine inlet underline the potential of the ejector to couple the RDC with an axial turbine. Total pressure fluctuations are dampened by 65%, whereas the Mach number and the total temperature distortion are reduced to acceptable levels.
Development of a filtered reaction rate model for the non-equimolar reaction
Authors: Wang Lingxue , Zhang Yu , Yu Yaxiong , Huang Zheqing , Zhou Qiang
Published: December 2024

In many applications, the chemical reaction changes the number of moles of the gas phase and hence affects the gas–solid flow structures and the reaction behavior. This study analyzes the effect of such non-equimolar reaction on the meso-scale reaction rate model. Based on the filter technique and the fine-grid simulation data, a meso-scale reaction rate model is proposed by correcting the model established by Huang et al. (AIChE, 2021, 67 (5)) in which only equimolar reaction is involved. The Reynolds number calculated by the filtered gas–solid slip velocity is found to be an important marker in the correction factor. The effectiveness of the new model is demonstrated by prior tests and also posteriori tests in fluidized beds.
Shear flow at openings and hydrophobic sliding at gaps: A method for fabricating deformable microlenses by extracting cavities from a liquid bath
Authors: Gu Tongkai , Peng Niming , Cai Anjiang , Wang Lanlan , Yin Lei , Liu Hongzhong
Published: December 2024

A novel approach for fabricating deformable microlens arrays using template-induced self-assembly technology is introduced. By utilizing shear flow at cavity openings and hydrophobic sliding at interstitial gaps, this method achieves precise liquid microlens formation without the need for complex mechanical systems. The process employs a template immersed in a glycerol bath, where interfacial forces enable the pinning of liquid droplets within specific microcavities. A combination of theoretical modeling and finite element simulations was used to investigate the effects of cavity radius, pulling speed, and static contact angle on microlens liquid height. Findings reveal that larger cavity radii and higher static contact angles enhance liquid height. However, increased pulling speeds initially raise the liquid level before a subsequent decrease. Experimentally, uniform microlens arrays were successfully fabricated, demonstrating consistent surface shapes with the liquid level height of 43 μm and remarkable imaging tunability under thermal stimuli, achieving a 2.22-fold focal length expansion. This work advances the understanding of droplet manipulation and offers promising applications in microfluidics, optical systems, and surface engineering.
Long short-term memory (LSTM) neural networks for in situ particle velocity determination in material strength experiments under ramp wave compression
Authors: Li Guoquan , Pan XinTong , Chen Xuemiao , Shui Rongjie , Xu Chao , Luo Binqiang , Wang Guiji , Tan Fuli , Zhao Jianheng , Sun Chengwei
Published: December 2024

In the experiments of measuring the strength of materials under ramp compression, accurately determining in situ particle velocity is crucial for calculating material sound speed during loading–unloading path and materials strength under high pressure. This paper proposes a machine learning approach that utilizes Long Short-Term Memory (LSTM) neural networks and Bayesian optimization algorithms to enhance the analysis of data from ramp compression strength measurement experiments. This method leverages LSTM neural networks to uncover the complex relationship between the rear interface velocity of the sample and the in situ particle velocity in numerical simulations. By using a well-trained network model, it enables direct interpretation of experimental data, leading to accurate predictions of key physical quantities along the loading and unloading paths in ramp compression experiments. A comparative analysis between theoretical curves from numerical simulations and LSTM neural network predictions shows a high degree of consistency. This approach is applied to ramp compression experiments on Ta and CuCrZr materials, demonstrating superior accuracy over the free-surface approximation and incremental impedance matching methods. Additionally, this method relies solely on the equation of state during numerical computations, eliminating the need for the complex constitutive equations required by the transfer function method, thus enhancing data processing efficiency and practicality.