bluuebunny/crossref_metadata_2025 huggingface dataset:
An impact-free mechanism to deliver water to terrestrial planets and exoplanets
Authors: Kral Quentin , Huet Paul , Bergez-Casalou Camille , Thébault Philippe , Charnoz Sébastien , Fornasier Sonia
Published: December 2024

Context. The origin of water, particularly on Earth, is still a matter of heated debate. To date, the most widespread scenario is that the Earth originated without water and that it was brought to the planet mainly as a result of impacts by wet asteroids coming from further out in space. However, many uncertainties remain as to the exact processes that supplied an adequate amount of water to inner terrestrial planets.

Aims. In this article, we explore a new mechanism that would allow water to be efficiently transported to planets without impacts. We propose that primordial asteroids were icy and that when the ice sublimated, it formed a gaseous disk that could then reach planets and deliver water.

Methods. We have developed a new model that follows the sublimation of asteroids on gigayear (Gyr) timescales, taking into account the variable luminosity of the Sun. We then evolved the subsequent gas disk using a viscous diffusion code, which leads to the gas spreading both inwards and outwards in the Solar System. We can then quantify the amount of water that can be accreted onto each planet in a self-consistent manner using our code.

Results. We find that this new disk-delivery mechanism is effective and equipped to explain the water content on Earth (with the correct D/H ratio) as well as on other planets and the Moon. Our model shows most of the water being delivered between 20 and 30 Myr after the birth of the Sun, when the Sun’s luminosity increased sharply. Our scenario implies the presence of a gaseous water disk with substantial mass for hundreds of millions of years, which could be one of the key tracers of this mechanism. We show that such a watery disk could be detected in young exo-asteroid belts with ALMA.

Conclusions. We propose that viscous water transport is inevitable and more generic than the impact scenario. We also suggest it is a universal process that may also occur in extrasolar systems. The conditions required for this scenario to unfold are indeed expected to be present in most planetary systems: an opaque proto-planetary disk that is initially cold enough for ice to form in the exo-asteroid belt region, followed by a natural outward-moving snow line that allows this initial ice to sublimate after the dissipation of the primordial disk, creating a viscous secondary gas disk and leading to the accretion of water onto the exo-planets.
Using Gaia and synthetic photometry for the absolute flux calibration of planetary cameras: The case of BepiColombo/SIMBIO-SYS
Authors: Munaretto G. , Cremonese G. , Bellazzini M. , Montegriffo P. , Sordo R. , La Grassa R. , Re C. , Tullo A. , Messineo M.
Published: December 2024

Context. The absolute flux calibration of a planetary camera is pivotal for a quantitative analysis of the brightness that is reflected by a celestial body to a) characterise its microphysical properties, b) analyse changes caused by exogenic or endogenic activity, and c) produce high-quality image mosaics to understand the geology of the body. This is usually done by observing a few standard stars. We propose an alternative method that relies on the Gaia catalogue and consider the Spectrometer and Imagers for Mpo Bepicolombo Integrated Observatory SYStem (SIMBIO-SYS) suite of imagers on board BepiColombo, which is currently flying towards planet Mercury, as a test case. We discuss the advantages of this method and its implications for the future exploration of Mercury, as well as the applicability to other cameras.

Aims. We evaluate whether Gaia low-resolution spectra (XPSP) are suitable to supply a set of reference stars for an absolute calibration of a planetary camera. We assess the performances of this approach and discuss its advantages with respect to more traditional methods. While this was validated for common astronomical facilities, it has never been used for planetary cameras.

Methods. We used synthetic photometry from Gaia low-resolution (BP/RP) spectra to produce magnitudes in all the passbands of SIMBIO-SYS. We used a set of very reliable spectrophotometric standard stars to correct small residual systematics that affect externally calibrated BP/RP spectra, and we thus defined the SIMBIO-SYS photometric system tied to the flux scale of the CALSPEC spectrophotometric library. We evaluated the uncertainties on the final calibration of this photometric system by assessing the accuracy (average of the residuals) and precision (standard deviation of the residuals) of the reproduced magnitudes of stars in the CALSPEC spectrophotometric library.

Results. We find an accuracy better than 0.1% and a precision ranging from 0.4% to 1.0%, depending on the considered passband, in the magnitude and colour ranges that are relevant for stars that can be used as photometric standards for the SIMBIO-SYS instrument.

Conclusions. Our results imply an improvement in the flux uncertainty through the absolute calibration of a factor 2–12 with respect to pre-existing imaging data of Mercury, and of a factor 2–7 with respect to the Colour and Stereo Surface Imaging System (CaSSIS), which is a similar camera with the same detector that orbits Mars, for which the absolute calibration details are available in the literature. In the context of the future exploration of Mercury, these improvements imply an unprecedented sensitivity of the SIMBIO-SYS instrument that will provide a novel view of the present-day surface activity on Mercury and of the photometric properties of the Hermean surface.
GI 725A b: A potential super-Earth detected with SOPHIE and SPIRou in an M dwarf binary system at 3.5 pc
Authors: Cortés-Zuleta P. , Boisse I. , Ould-Elhkim M. , Wilson T. G. , Larue P. , Carmona A. , Delfosse X. , Donati J.-F. , Forveille T. , Moutou C. , Collier Cameron A. , Artigau É. , Acuña L. , Altinier L. , Astudillo-Defru N. , Baruteau C. , Bonfils X. , Cabrit S. , Cadieux C. , Cook N. J. , Decocq E. , Díaz R. F. , Fouqué P. , Gomes da Silva J. , Grankin K. , Grouffal S. , Hara N. , Hébrard G. , Heidari N. , Martins J. H. C. , Martioli E. , Maurice M. , Scigliuto J. , Serrano Bell J. , Sulis S. , Petit A. C. , Vivien H. G.
Published: December 2024

We report the discovery of a super-Earth candidate orbiting the nearby mid-M dwarf Gl 725A using the radial velocity (RV) method. The planetary signal has been independently identified using high-precision RVs from the SOPHIE and SPIRou spectrographs, in the optical and near-infrared (NIR) domains, respectively. We modelled the stellar activity signal jointly with the planet using two Gaussian processes, one for each instrument to account for the chromaticity of the stellar activity and instrumental systematics, along with a Keplerian model. The signal was significantly detected with a RV semi-amplitude of 1.67 ± 0.20 m/s. The planet Gl725A b is found to be in an orbit compatible with circular with a period of 11.2201 ± 0.0051 days. We analysed 27 sectors of TESS photometry, for which no transit event was found. We determined a minimum mass of Mp sin i = 2.78 ± 0.35 M⊕, which places the planet in the super-Earth regime. Using mass-radius relationships, we predict the planetary radius to be between 1.2 and 2.0 R⊕. The proximity of Gl 725A (at only 3.5 pc) makes this new exoplanet one of the closest to Earth and joins the group of S-type low-mass planets in short orbits (P < 15 days) around close M dwarfs.
The distribution of the near-solar bound dust grains detected with Parker Solar Probe
Authors: Kočiščák S. , Theodorsen A. , Mann I.
Published: December 2024

Context. Parker Solar Probe (PSP) counts dust impacts in the near-solar region, but modeling effort is needed to understand the dust population’s properties.

Aims. We aim to constrain the dust cloud’s properties based on the flux observed by PSP.

Methods. We developed a forward model for the bound dust detection rates using the formalism of 6D phase space distribution of the dust. We applied the model to the location table of different PSP solar encounter groups. We explain some of the near-perihelion features observed in the data as well as the broader characteristic of the dust flux between 0.15 AU and 0.5 AU. We compare the measurements of PSP to the measurements of Solar Orbiter near 1 AU to expose the differences between the two spacecraft.

Results. We found that the dust flux observed by PSP between 0.15 AU and 0.5 AU in post-perihelia can be explained by dust on bound orbits and is consistent with a broad range of orbital parameters, including dust on circular orbits. However, the dust number density as a function of the heliocentric distance and the scaling of detection efficiency with relative speed are important to explain the observed flux variation. The data suggest that the slope of differential mass distribution, δ, is between 0.14 and 0.49. The near-perihelion observations, however, show the flux maxima, which are inconsistent with the circular dust model, and additional effects may play a role. We found an indication that the sunward side of PSP is less sensitive to the dust impacts than PSP’s other surfaces.

Conclusions. We show that the dust flux on PSP can be explained by noncircular bound dust and the detection capabilities of PSP. The scaling of flux with impact speed is especially important, and shallower than previously assumed.
A sub-Earth-mass planet orbiting Barnard’s star
Authors: Stefanov A. K. , González Hernández J. I. , Suárez Mascareño A. , Nari N. , Rebolo R. , Damasso M. , Castro-González A. , Zapatero Osorio M.-R. , Allende Prieto C. , Silva A. M. , Martins C. J. A. P.
Published: December 2024

A sub-Earth-mass planet orbiting Barnard’s star, designated as Barnard b, has recently been announced. At almost the same time, the first photometric data of Barnard’s star by the Transit Exoplanet Survey Satellite (TESS) was released in Sector 80. We explore the possibility of emergent transits of Barnard b in TESS photometry. The detrended 2 min light curve appears to be flat, with a flux root mean square of 0.411 parts per thousand. Attempts of blind and informed transit curve model inference suggest no evidence of transiting Barnard b, or any other body. This provides a 3σ upper bound of 87.9 degrees for the orbital inclination of Barnard b.
First detection of a deuterated molecule in a starburst environment within NGC 253
Authors: Butterworth J. , Martín S. , Rivilla V. M. , Viti S. , Aladro R. , Colzi L. , Fontani F. , Harada N. , Henkel C. , Jiménez-Serra I.
Published: December 2024

Context. Deuterium was primarily created during the Big Bang nucleosynthesis. This fact, alongside its fractionation reactions resulting in enhanced abundances of deuterated molecules, means that deuterium abundances can be used to better understand many processes within the interstellar medium as well as its history. Previously, observations of deuterated molecules have been limited to the Galaxy, the Magellanic Clouds, and (with respect to HD) to quasar absorption spectra.

Aims. We present the first robust detection of a deuterated molecule in a starburst environment and, apart from HD, the first one detected outside the Local Group. As such, we could constrain the deuterium fractionation as observed by DCN.

Methods. We observed the central molecular zone (CMZ) of the nearby starburst galaxy NGC 253 covering multiple giant molecular clouds (GMCs) with cloud scale observations (∼30 pc) using the Atacama Large Millimeter/submillimeter Array. Via the MADCUBA package, we were able to perform local thermodynamic equilibrium analysis in order to obtain deuterium fractionation estimates.

Results. We detected DCN in the nuclear region of the starburst galaxy NGC 253 and estimated the deuterium fractionation (D/H ratio) of DCN within the GMCs of the CMZ of NGC 253. We found a range of 5 × 10−4 to 10 × 10−4, which is relatively similar to the values observed in warm galactic star-forming regions. We also determined an upper limit of D/H of 8 × 10−5 from DCO+ within one region, closer to the cosmic value of D/H.

Conclusions. Our observations of deuterated molecules within NGC 253 appear to be consistent with previous galactic studies of star-forming regions. This implies that warmer gas temperatures increase the abundance of DCN relative to other deuterated species. This study also further expands the regions, particularly in the extragalactic domain, in which deuterated species have been detected.
Stellar halos of bright central galaxies
Authors: Contini Emanuele , Spavone Marilena , Ragusa Rossella , Iodice Enrichetta , Yi Sukyoung K.
Published: December 2024

Aims. We present theoretical predictions and extrapolations from observed data of the stellar halos surrounding central group and cluster galaxies, and the transition radius between them and the intracluster or diffuse light.

Methods. Leveraging the state-of-the-art semi-analytic model of galaxy formation, FEGA (Formation and Evolution of GAlaxies), applied to two dark matter-only cosmological simulations, we derived both the stellar halo mass and its radius. Using theoretical assumptions about the diffuse light distribution and halo concentration, we extrapolated the same information for observed data from the VEGAS survey.

Results. Our model, supported by observational data and independent simulation results, predicts an increasing transition radius with halo mass, a constant stellar halo-to-intracluster light ratio, and a stable stellar halo mass fraction with increasing halo mass. Specifically, we find that the transition radius between the stellar halo and the diffuse light ranges from 20 to 250 kpc, from Milky Way-like halos to large clusters, while the stellar halo mass comprises only a small fraction, between 7% and 18%, of the total stellar mass within the virial radius.

Conclusions. These results support the idea that the stellar halo can be viewed as a transition region between the stars bound to a galaxy and those belonging to the intracluster light and are consistent with recent observations and theoretical predictions.
The role of fisheries and aquaculture products in ensuring sustainable and healthy food consumption in France
Authors: Dewals Jean-François , Daures Fabienne , Le Floc’h Pascal
Published: December 2024

The consumption of Fisheries and Aquaculture Products (FAP) can contribute to the transition of our food system towards greater sustainability. However, in order to implement effective food policies aimed at promoting sustainable FAP consumption, data on individual consumption behavior are lacking. Based on a consumer survey carried out on the French market in 2023, the aim of this article was to gain a deeper understanding of the current consumption patterns in place in France in order to identify potential levers for aligning French FAP consumption with public health and resource conservation objectives. Using an ordered probit model and Welch’s t-tests, our results show that French FAP consumption is currently driven by few people (the elderly, connoisseurs, and high-income households). In line with our findings, actions are proposed to guide French FAP consumers towards more sustainable behavior. In particular, we discuss the need to inform and educate consumers better. The promotion of local “under-utilized” species, the integration of environmental considerations into existing food policies, or even the need to exploit “out-of-home” consumption venues to promote sustainable FAP consumption among occasional consumers are discussed as interesting possibilities.
Propagating parabolic rotational beams, new family of accelerated beams
Authors: Espíndola-Ramos Ernesto , Gómez-Correa Jesús Emmanuel , Hernández-Nolasco José Adán , Chávez-Cerda Sabino
Published: December 2024

A novel class of structured propagating waves with parabolic rotational symmetry is introduced for the first time. These are described by exact solutions of the non-paraxial Helmholtz equation. As a result of the separability of the Helmholtz equation, the intensity of these wavefields remains invariant while propagating along parabolic trajectories, thus exhibiting apparent acceleration. We will show that superposition of the fundamental traveling waves can present parabolic, spherical or even rectilinear propagation.
Umsetzung der DGPPN-S3-Leitlinie zur Prävention von Gewalt und Zwang:
Prä-post-Analyse der randomisierten kontrollierten PreVCo-Studie
Authors: Hirsch Sophie , Baumgardt Johanna , Bechdolf Andreas , Bühling-Schindowski Felix , Cole Celline , Flammer Erich , Jaeger Susanne , Junghanss Julia , Kampmann Marie , Sauter Dorothea , Muche Rainer , Vandamme Angelika , Steinert Tilman , Mahler Lieselotte
Published: December 2024

Ziel der Studie In der vorliegenden Arbeit wird untersucht, inwieweit eine
strukturierte Implementierung der Leitlinie zur Vermeidung von Zwang zu einer
Verbesserung leitlinienkonformen Arbeitens und der Reduktion von Zwang in der
klinischen Arbeit führt.

Methodik Die vorliegende Arbeit ist eine Sekundäranalyse der Daten der
PreVCo-Studie, welche deutschlandweit auf 55 psychiatrischen Stationen
durchgeführt wurde.

Ergebnisse Die Anzahl der Zwangsmaßnahmen ging im Beobachtungszeitraum
signifikant zurück. Der Grad der Umsetzung der Leitlinien stieg signifikant an.
Dies konnte ohne Zunahme von aggressiven Übergriffen erreicht werden.

Schlussfolgerung Die strukturierte Implementierung leitliniengerechten
Arbeitens ist im Routinebetrieb auf psychiatrischen Stationen möglich.
Indium-Catalyzed Tandem Cyanomethylation/Cyclization of α-Alkynyl α,β-unsaturated Ketones with 3-Azido-2-methylbut-3-en-2-ol toward Trisubstituted Furans
Authors: Zhang Zhihao , Zhang Xudong , Xu Minghui , Wang Bi-Qin , He Rui , Chen Bin , Hu Ping , Cao Peng
Published: December 2024

An indium-catalyzed cyanomethylation of α-alkynyl α,β-unsaturated ketones with 3-azido-2-methylbut-3-en-2-ol is presented. Furan-substituted propanenitriles were produced in yields of 29–97%. The reaction involves a nucleophile addition/cycloisomerization process.
Insurtech strategies: a comparison of incumbent insurance firms with new entrants
Authors: Holland Christopher P. , Kavuri Anil S.
Published: December 2024

Insurtech is closely associated with digital transformation by new entrants that seek to disrupt insurance markets. However, the insurtech concept also includes its use by incumbent insurance companies, which are actively deploying a wide variety of insurtech applications to protect their market positions through innovation of their existing business models, e.g. through improved business processes or new insurance services. A theoretical insurtech business innovation model is developed that captures the effects of digital technology in insurance markets by considering innovation as a multi-dimensional concept that encompasses business processes, novel insurance products and changes to the insurance value chain. This framework is applied to an empirical sample of digital leaders: three incumbents and four new entrants. The results illustrate a variety of insurtech applications that include the transformation of business processes, products and new types of value chain configuration, as well as relatively minor enhancements to existing systems and business practices. It is shown that all the new entrants exploit artificial intelligence, big data and digital technology to build brand-new insurance services that emphasise innovative product features, high customer value and a delightful customer experience. In contrast, the legacy insurance firms tend to use digital technology in a defensive manner, e.g. the enhancement of existing insurance services, distribution channels and market positions. The exception is the launch of a telematics insurance service by an incumbent firm, where the telematics insurance effectively operates as a standalone business within a legacy insurance firm. The theory model is effective at analysing and evaluating both the type and magnitude of innovation. The case studies make an empirical contribution by illustrating state-of-the-art innovation by insurance disruptors and contrasts this with the defensive and sometimes novel digital strategies of incumbent firms. Future trends and research opportunities are outlined.
The Russian invasion of Ukraine and changes in MEPs’ conceptions of security
Authors: Kakhishvili Levan , Felder Alina
Published: December 2024

Options of organizing security are often determined by how it is conceived. The paper focuses on how European security has been discussed in the European Parliament in response to the Russian annexation of Crimea in 2014 and the Russian invasion of Ukraine in 2022. Drawing on parliamentary debates and meaning-making of security, we construct a threefold argument. Firstly, when MEPs discuss whose security needs to be addressed, we observe no significant changes between 2014 and 2022, but a decrease in the imagined distance between the EU and Ukraine and increase in the animosity toward Russia. Secondly, we show that security is continuously defined more broadly and extends to issues such as food, cyber, and civilian security. Finally, organizing security is increasingly viewed in competitive terms as opposed to a cooperative approach with Russia and has a strong focus on the EU’s independent agency in 2022.
Enhancing short-term power forecasting of PV clusters: A statistical upscaling and CBAM-BiLSTM approach
Authors: Ouyang Jing , Zuo Zongxu , Wang Qin , Duan Qiaoning , Qin Long
Published: December 2024

Traditional short-term solar power forecasting primarily focuses on individual photovoltaic (PV) plants. Recently, there has been increasing demand for power forecasting of PV clusters. In this paper, a distributed PV cluster power prediction model based on statistical upscaling and convolutional block attention module (CBAM)–bi-directional long short term memory (BiLSTM) is proposed to strike a balance between prediction accuracy and model training time. To address the issue of inaccurate cluster partitioning caused by variations in distributed PV output curves, a K-shape based cluster partitioning method is proposed. This method effectively reduces the number of prediction scenarios. Furthermore, a soft-dynamic time warping based representative power plants selection method is introduced to accurately identify representative power plants from sub-clusters. This selection method takes into account the horizontal and vertical stretching of the output curves, ensuring a comprehensive reflection of curve similarity. To minimize the conversion error during cluster transformation, a real-time statistical upscale conversion method is proposed. This method considers multiple similar output days, resulting in more accurate sub-cluster output predictions. The hybrid model, which employs CBAM for initial feature extraction and BiLSTM for output forecasting, is introduced to predict the output of representative power stations. Finally, the effectiveness of the proposed model is verified through evaluation indices, with the mean absolute percentage error value of the representative power station being less than 5%. The accuracy of the results is further supported by the confidence interval analysis.
Neutron-induced backgrounds in coaxial cables on the South Pole neutron time-of-flight detector at the National Ignition Facility
Authors: Kerr S. , Jeet J. , Mariscal E. , Hahn K. D. , Eckart M. J. , Khater H. , Bionta R. M. , Casey D. , Carrera J. , Delora-Ellefson J. , Hartouni E. P. , Schlossberg D. J.
Published: December 2024

As neutron yields increase at fusion facilities, a universal symptom the community must deal with is MeV neutron-induced backgrounds in cables running to diagnostics. On the first Gain >1 plasmas in the world, the National Ignition Facility (NIF) neutron time-of-flight (nToF) diagnostic registered significant cable backgrounds that compromised key performance measurements. The South Pole nToF is uniquely located inside the NIF Target Bay shield walls, ∼18 m from the fusion source, and consequently has long coaxial cable runs (>20 m) that see significant neutron fluence. The resulting neutron-driven current in the cable is comparable to the downscattered neutron signal, compromising the downscattered ratio (DSR) measurement. We have characterized this background with a series of on-shot tests and developed a background subtraction technique to mitigate these effects. The background subtracted DSR results are validated against zirconium activation measurements, indicating that we have successfully reclaimed high-quality data output. The ion temperature measurement is found to not be affected by this background. Alternative approaches to addressing neutron-induced cable backgrounds are presented for potential future hardware upgrades.
Geometric preprocessing for measurements of comet 67P acquired by Rosetta’s Visible and InfraRed Thermal Imaging Spectrometer, Mapping channel (VIRTIS-M)
Authors: Kappel D. , Arnold G. , Filacchione G. , Capaccioni F. , Tosi F. , Erard S. , Ciarniello M. , D’Aversa E. , Raponi A. , Leyrat C. , Moroz L. V.
Published: December 2024

Comet 67P/Churyumov–Gerasimenko (hereafter 67P) was the primary target of ESA’s Rosetta mission. Hyperspectral images acquired by the Mapping channel of the Visible and InfraRed Thermal Imaging Spectrometer aboard Rosetta can be used to derive physical and compositional surface properties by detailed spectrophotometric analyses. This calls for a precise spatial co-registration between measurements and geometry information. In this work, we improve the wavelength-dependent co-registration and also the spatial consistency of the radiometric calibration. This is accomplished by applying a feature-based image matching method comparing measured 67P nucleus images from the entire mission to corresponding photometric simulations. The derived geometric distortions suggest previously unaccounted optical aberrations of the instrument, in conjunction with non-systematic spacecraft pointing and perspective errors, and discrepancies between the true nucleus shape at data acquisition time and the used digital shape model.
Development of an atmospheric boundary layer detection system based on a rotary-wing unmanned aerial vehicle
Authors: You Guang , Yang Jie , Wang Xiaotian , Liu Qingquan , Ding Renhui
Published: December 2024

To enhance meteorological detection methods, an atmospheric boundary layer detection system based on a rotary-wing unmanned aerial vehicle (UAV) was proposed. Computational fluid dynamics (CFD) was employed to model the surrounding airflow distribution during UAV hovering, thereby determining the optimal positions for sensor installation. A novel radiation shield was designed for the temperature sensor, offering both excellent radiation shielding and superior ventilation. To further improve temperature measurement accuracy, an error correction model based on CFD and neural network algorithms was designed. CFD was used to quantify the temperature measurement errors of the sensor under different environmental conditions. Subsequently, random forest and multilayer perceptron algorithms were employed to train and learn from the simulated temperature errors, resulting in the development of the error correction model. To validate the accuracy of the detection system, comparative experiments were conducted using the measurement values from the 076B temperature observation instrument as a reference. The experimental results indicate that the mean absolute error, root mean square error, and correlation coefficient between the experimental temperature errors and the algorithm-predicted errors are 0.055, 0.066, and 0.971 °C, respectively. The average error of the corrected temperature data is 0.05 °C, which shows substantial agreement with the reference temperature data. During UAV hovering, the average discrepancies between the temperature, humidity, and air pressure data of the detection system and the ground-based reference data are 0.6 °C, 1.6% RH, and 0.77 hPa, respectively.
Insight into gain and transient response characteristics of AlGaN/GaN hetero-junction based UV photodetectors: Case study on the role of incident light intensity
Authors: Li Wenxin , Wang Yifu , Gu Guangyang , Ren Fangfang , Zhou Dong , Xu Weizong , Zhou Feng , Chen Dunjun , Zhang Rong , Zheng Youdou , Lu Hai
Published: December 2024

Gain and response speed are two key performance parameters for high sensitivity photodetectors (PDs). However, the effect of incident light intensity on gain and transient response properties of AlGaN/GaN hetero-junction based PDs are still not fully understood. Here, we design and fabricate an AlGaN/GaN hetero-junction based ultraviolet (UV) PD with interdigitated electrodes formed by a conductive two-dimensional electron gas (2DEG) channel, which exhibits a low dark current of 2.92 × 10−11 A and a high responsivity of 3060 A/W at 10 V bias. The high-gain AlGaN/GaN 2DEG PD has a similar working mechanism to those of traditional phototransistors, but its device architecture is evidently simplified. By investigating the variation of gain and transient response characteristics of the 2DEG PD as a function of incident UV light intensity, it has been concluded that the gain of the PD in a low-light intensity region is dominated by hole accumulation-induced electron escape from the 2DEG, while in a high-light intensity region, the gain is dominated by photoconductivity effect and limited by carrier recombination. This study provides guidance for future practical applications of AlGaN/GaN-based PDs in complex UV illumination environments.
Structural, dielectric, impedance, and ferroelectric studies of LiNbO3-doped K0.5Na0.5NbO3 ceramics
Authors: Kumar Raju , Singh Satyendra
Published: December 2024

Currently, sophisticated advanced electronics require ferroelectric materials with high dielectric response. Lead-free (1−x)K0.5Na0.5NbO3-xLiNbO3 (KNN-xLiN) ceramics with x = 0.01, 0.03, and 0.05 were produced using a solid-state method, resulting in a greater dielectric constant, a lower impedance, and an increased conductivity. Compared to conventional ferroelectrics, KNN-0.01LiN ceramics have a greater activation energy (Erel) of 1.33 eV and a large σac value of 10−3− 10−2 S/m in the frequency range of 20 Hz–1 MHz. The peak that corresponds to the orthogonal–tetragonal (TO−T) phase shifts toward the lower temperature side and the peak that corresponds to TT−C shifts toward the higher temperature side as dopant percentage increases in the KNN-xLiN ceramics. The observed data may provide light on a key member of the team involved in the creation of upgraded ferroelectrics with improved performance. This result sheds light on the process underlying the improved characteristics of K0.5Na0.5NbO3-based ceramics and may lead to the development of high performance ferroelectrics that will benefit a variety of functional materials.
Effects of oscillation frequency, phase difference, and arrangement of two triangular cylinders on the hydrothermal performance of a channel
Authors: Abbasinezhad Fallah Davoud , Rezazadeh Sajad , Dadvand Abdolrahman , Sadeghi Haleh
Published: December 2024

This study aims to numerically explore the effects of two cylinders with triangular cross sections, undergoing transverse oscillation on the heat and fluid flow within a channel. The governing equations along with the pertinent initial and boundary conditions are solved using the finite element method. The results are validated against the available data in the literature, demonstrating admissible agreement. Different oscillation frequencies, phase differences, and arrangement of the cylinders are considered. The results are presented in terms of temperature, pressure, and vorticity contours, alongside the Nusselt (Nu) number and thermal performance index (TPI). The Reynolds number based on the triangle's side length (Reb=200) is deliberately chosen to induce the vortex shedding phenomenon in the wake of the cylinders. For a single oscillatory cylinder, an optimal oscillation frequency fr=0.5 was found resulting in a remarkable increase in 22.3% and 33.1% in the Nu number and TPI, respectively, when compared to the fixed single cylinder. Using the obtained optimal oscillation frequency fr=0.5, the side-by-side arrangement of two cylinders gives rise to a higher TPI than the tandem one. The maximum TPI in side-by-side arrangement corresponds to the oscillation phase of φ=π/6, which is about 1.69. In tandem arrangement, it corresponds to φ=π/3, which is approximately 1.3. Furthermore, the oscillation phase φ=π exhibits the lowest TPI for both arrangements.
Soft x-ray tomography using L1 regularization for MHD modes with limited sight lines in JT-60SA
Authors: Bando T. , Takechi M. , Ohdachi S.
Published: December 2024

Soft x-ray (SX) tomography is a useful diagnostic in fusion research, and a multi-channel SX diagnostic will be installed in JT-60SA, the largest elongated tokamak in the world. However, in the SX diagnostic of JT-60SA, plasmas will be only viewed from the low field side and the upper side of plasmas; the sight lines are limited, which would be common in future devices as well as JT-60SA. This kind of limited sight lines is not preferred for SX tomography to investigate the spatial structure of magnetohydrodynamics (MHD) modes because inadequate information of plasmas makes artifacts in the reconstructed SX profiles. One of the solutions to reduce the artifacts is to employ L1 regularization, which gives the essential and sparse contributions [Kaptanoglu et al., Phys. Plasmas 30, 033906 (2023)]. In this study, as a first topic, the applicability of L1 regularization to reduce the artifacts in SX tomography with limited sight lines is investigated with traditional L2 regularization for a high beta scenario of JT-60SA where MHD modes would occur. Here, as a series of basis functions, the Fourier–Bessel series (FBS) is employed because FBS has the poloidal Fourier modes explicitly. A disadvantage of FBS is that the accurate equilibrium inside the last closed flux surface (LCFS) is needed; interior measurement such as the motional Stark effect measurement is required, which is not always available during a whole discharge. The second topic of this study is to investigate other appropriate basis functions to study the spatial structure of MHD modes in elongated tokamak plasmas. Here, we introduce Saito’s Laplacian eigenfunction (LEF). Saito’s LEF can be calculated if LCFS is given and the LEF is expected to show the explicit poloidal Fourier mode. Because the calculation of LCFS with magnetic measurements is a basic task of plasma operations, Saito’s LEF may be used anytime. Our investigation showed that L1 regularization can strongly improve the SX tomography with the traditional L2 regularization having FBS/LEF and would be effective against other tomographic problems in fusion devices.
Effect of depth ratio on frozen wave instability in immiscible liquids
Authors: Choudhary K. P. , Das S. P. , Tiwari Shaligram
Published: December 2024

In the present experimental work, a two-liquid system with comparable densities (density ratio = 0.543) undergoing lateral sinusoidal oscillation [along the length (L) of the container] has been considered. Under high forcing frequency condition (ω≫ν/L2), frozen waves appear at the interface of two-liquid system. Different depth ratios (hr) (or filling levels of liquid-1 and liquid-2) have been used to investigate the variations in the instability thresholds, wave amplitudes, wavelengths, and wave profiles of the frozen waves. Instability threshold of frozen waves shows unidirectional nature with varying depth ratios. A coefficient of relative velocity (c1) has been used to non-dimesionalize the variation of threshold amplitude (Aoc) and wave amplitude (Ar) with respect to depth ratios. Variation of normalized wave amplitude with modified Froude number shows existence of two regimes viz. gravity and surface tension dominated beyond which waves become three dimensional. A significant variation in wave profiles has been observed at high amplitude of forcing and reported in terms of radius of curvature. The three-dimensional frozen waves with temporally and spatially periodic doubling have been discussed.
Novel mechanical-dynamical aspects with native Nepalese complex granular slides
Authors: Pudasaini Shiva P. , Dangol Bekha R. , Tiwari Chet N. , Kattel Parameshwari , Pokhrel Puskar R. , Kafle Jeevan
Published: December 2024

We perform chute-flow experiments with native Nepalese fruit seed Champati with epitomic physical properties. Considering supergrain Champatis as a primary material, we add food-grains Gahat and Silam, forming Champati-Gahat and Champati-Silam mixtures with different properties. We study their interactions with structures. Dynamical and depositional characteristics of Gahat and Silam are predictable; however, Champatis exhibit unpredictable hypermobility and superspreading. Mixture mobility is reduced as compared with Champati. Astonishingly, mixtures result in tremendously reduced spreading of Champati but enhanced spreading of Gahat and Silam because Champati provides them with thrust, experiencing anti-thrust in return. We present first demonstration of rapidly intensifying strong phase-separation as mixtures slide down unconstrained slope. Separation-length is enormous for Champati–Silam mixture with Champati-dominant front and strong Silam-dominant rear. Outright spectacular separation evolves between them. Eye-catching phenomenon is that front speeds of Champati-Gahat and Champati-Silam are similar: Gahat applies strong resistance against Champati; Champati incredibly propels Silam. Mixture deposition profiles are in-between their constituents. Fascinating is the substantially higher relative acceleration of Champati in Champati-Silam than in Champati-Gahat flow. Propagation rate of Silam at rear of Champati-Silam is very low with much delayed incipient motion of its rear. After flow-tetrahedral structure interactions, dissipated kinetic energy alters flow dynamics and deposition-pattern. Rearward-facing tetrahedron causes more mass-arrest, increased deposition-depth, backward propagating shocks, and crosswise runout extents but decreased longitudinal extent than forward-facing tetrahedron. Process and civil engineering can substantially benefit from our novel findings. Results contribute to better understanding of hypermobility, superspreading, and phase-separation of some geological flows, including fragmented rock avalanches, and assist in addressing some relevant standing challenges.
Aerodynamic design optimization of the hypersonic inward turning inlet in wide-speed range
Authors: Qu Feng , Wang Xiaofeng , Zhong Jiaxiang , Qu Haoyang
Published: December 2024

A multipoint optimization based on the discrete adjoint optimization method in a wide-speed range is carried out to improve the performance of the hypersonic inlet with a rectangular to elliptical shape transition. The optimization framework is established based on the discrete adjoint method and combined with the free form deformation method, the mesh deformation method, and the high-accuracy Reynolds averaged Navier–Stokes solver. A total of 3180 design variables are employed during the optimization, and the optimum result is obtained after 67 iterations of adjoint optimization. The results indicate that the performance of the optimized inlet is significantly improved under both design and off-design conditions, while better improvements are obtained under off-design conditions. Thereafter, the mechanism of the performance enhancement is investigated by comparing the flow patterns of the original inlet with the optimized inlet under different operating conditions. Furthermore, the optimization results demonstrate that requirements for the localized deformation to enhance the inlet performance at each Mach number may be contradictory because of the different flow patterns under various operating conditions. As a result, the optimized result can be only a tradeoff between the constraints in wide-speed ranges.
Time-dependent quantum/continuum modeling of plasmon-enhanced electronic circular dichroism
Authors: Biancorosso L. , D’Antoni P. , Corni S. , Stener M. , Coccia E.
Published: December 2024

In this work, we present a multiscale real-time approach to study the plasmonic effects of a metal nanoparticle (NP) on the electronic circular-dichroism (ECD) spectrum of a chiral molecule interacting with it. The method is based on the time-evolution of the molecule’s time-dependent wavefunction, expanded in the eigenstates of a perturbed Hamiltonian. A quantum description of the molecular system is coupled to a classical representation of the NP via a continuum model. The method is applied to methyloxirane and peridinin at various distances (1, 3, and 5 nm) with respect to a gold NP surface. While no remarkable effect is observed for methyloxirane at any studied distance, an enhancement appears when the peridinin lies at 1 nm and the pulse is linearly polarized perpendicularly to the molecular axis, with the ECD signal centered at 4.1 eV increased by a factor of around 20. These results are rationalized looking at the gap between the plasmonic peak of the NP at around 2.5 eV and the molecular excitations: the smaller the gap between molecular and plasmonic excitations, the larger the plasmonic enhancement of the ECD signal. Moreover, ECD peaks are selectively enhanced due to the favorable coupling between the pulse polarization and the combined effect of electric and magnetic dipole moments. This approach allows one to go through the electronic structure and dynamics of chiral molecules for obtaining a realistic description of plasmon-mediated ECD spectra, e.g., paving the way to applications to molecules of biological relevance interacting with nanostructures of experimental interest.
Flow characteristics induced by a multiform windbreak in complex terrains with and without a train: A simplified method for calculating aerodynamic loads
Authors: Gao Hongrui , Liu Tanghong , Chen Xiaodong , Zeng Haoyang , Chen Guang , Chen Zhengwei , Zhang Jie , Khoo Boo Cheong
Published: December 2024

This study aims to investigate common multiform windbreaks, aligned parallel to railway tracks and perpendicular to incoming wind, in complex terrains. Using unsteady simulations, the study analyzes airflow downstream of these windbreaks and the aerodynamic characteristics during train passage. It evaluates the wind-protection performance of various windbreak types and transitions and identifies factors that influence performance. Results indicate that the vertical surface walls offer stronger wind protection compared to slope walls or viaduct barriers. Flow patterns near transitions reveal that upstream airflow shifts longitudinally from high-performance windbreaks to lower-performance ones, reentering the railway line space from the latter. This suggests a design approach in which neighboring windbreaks exhibit similar performance to optimize protection. On aerodynamic characteristics of the train, the maximum side force on the leading vehicle is found proportional to wind speed and train speed to the powers of 1.6 and 0.5, respectively; train speed affects the pressure on the streamlined head and the vortices around the leeward side. A simplified calculation for aerodynamic loads on a vehicle is proposed and explored with a consideration of wind speed above the railway line. An error margin of the maximum side force by this simplified method is 8.4%, and the saving is at least 88.2% of the computational resources when assessing the crosswind stability of a vehicle. The proposed design for the multiform windbreak, along with the simplified calculation method, can improve the performance of a multiform windbreak and increase the efficiency of assessing crosswind safety for railway operations downstream of the windbreak.
Ultra-broadband detection by photovoltaic and thermoelectric coupling based on large-scale single-crystalline SnSe thin film
Authors: Zhang Xianjing , Liu Fengliang , Wan Yu , Guo Bowen , Wang Qisheng
Published: December 2024

Recently, the layered tin selenide (SnSe) has attracted intense attention from the researchers due to its distinguished thermoelectric properties, thus giving this compound quite a promising potential application for photothermoelectric detectors. However, the low-cost epitaxial growth method toward a millimeter scale single phase SnSe thin film is still rarely reported, thus limiting its fabrications in arraying photoelectric sensors. Here, we synthesized a large-scale SnSe thin film on the SrTiO3 substrate by using the crack of PbS thin film-assisted nucleation in the chemical vapor deposition, achieving a homogeneous single-crystal SnSe thin film with a centimeter scale, as revealed by the x-ray diffraction and scanning electron microscope measurement. In addition, a two-terminal device is fabricated to study the photoelectric properties of this film. Surprisingly, this SnSe detector shows a synergetic photovoltaic and thermoelectric effect, achieving an ultrabroad band detection ranging from visible (405 nm) to mid-infrared (10.0 μm) at room temperature. Significantly, this detector also shows an impressive performance with an optimized response time of 2.81 ms (at 4.0 μm), a responsivity of 290.9 V W−1 (at 4.0 μm), and a detectivity of 5.5×108 Jones (at 4.0 μm). The above results addressed the bottleneck in SnSe film synthesis, and accelerated its applications in future high-performance photoelectronic devices.
Dynamic simulation of ion evaporation from a conductive meniscus, fluid-fluid model of plume and meniscus interactions
Authors: Huang Chengjin , Zhang Hongping , Chen Shi , Lin Jianhui , Qu Xi , Zhou Cangtao , Li Mu
Published: December 2024

Ion evaporation from a conductive meniscus has been of significant interest in the theoretical investigation of electro-hydrodynamics and application exploration across various fields. This study focuses on developing a fluid-fluid methodology for the dynamical simulation of a conductive meniscus undergoing ion evaporation and uncovering the interaction between the plume and meniscus using the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as a case study. In the fluid-fluid model, we propose a simplified fluid plume model to acquire the charge distribution in free space, and validate it against a particle plume model and a full fluid plume model. The meniscus evolution is described by expanding the leaky dielectric model to account for charge conservation in the liquid as well as self-heating and inhomogeneous physical properties. The arbitrary Lagrangian–Eulerian method is used to track the sharp liquid–vacuum interface. Dynamic simulation with the simplified fluid plume model is more than 150 times faster than that with the full fluid plume model. The electrohydrodynamic process of the meniscus evolving to form a droplet is analyzed, with a detailed discussion on the space charge effect caused by evaporated ions. Results indicate that neglecting the space charge effect during conical meniscus formation leads to a singular meniscus tip. Instead, the reverse electric field induced by the space charge suppresses this singularity, assisting the conical meniscus to produce a jet. Additionally, the high-throughput ion evaporation significantly enlarges the diameter of droplet formed on the conical meniscus due to the reverse electric field of space charge.