bluuebunny/crossref_metadata_2025 huggingface dataset:
Dust growth and pebble formation in the initial stages of protoplanetary disk evolution
Authors: Vorobyov Eduard I. , Kulikov Igor , Elbakyan Vardan G. , McKevitt James , Güdel Manuel
Published: January 2024

Aims. The initial stages of planet formation may start concurrently with the formation of a gas-dust protoplanetary disk. This makes the study of the earliest stages of protoplanetary disk formation crucially important. Here we focus on dust growth and pebble formation in a protoplanetary disk that is still accreting from a parental cloud core.

Methods. We have developed an original three-dimensional numerical hydrodynamics code, which computes the collapse of rotating clouds and disk formation on nested meshes using a novel hybrid Coarray Fortran-OpenMP approach for distributed and shared memory parallelization. Dust dynamics and growth are also included in the simulations.

Results. We found that the dust growth from ~1 µm to 1–10 mm already occurs in the initial few thousand years of disk evolution but the Stokes number hardly exceeds 0.1 because of higher disk densities and temperatures compared to the minimum mass Solar nebular. The ratio of the dust-to-gas vertical scale heights remains rather modest, 0.2–0.5, which may be explained by the perturbing action of spiral arms that develop in the disk soon after its formation. The dust-to-gas mass ratio in the disk midplane is highly nonhomogeneous throughout the disk extent and is in general enhanced by a factor of several compared to the fiducial 1:100 value. Low St hinders strong dust accumulation in the spiral arms compared to the rest of the disk and the nonsteady nature of the spirals is also an obstacle. The spatial distribution of pebbles in the disk midplane exhibits a highly nonhomogeneous and patchy character. The total mass of pebbles in the disk increases with time and reaches a few tens of Earth masses after a few tens of thousand years of disk evolution.

Conclusions. We found that protoplanetary disks with an age ≤20 kyr can possess notable amounts of pebbles and feature dust-togas density enhancements in the disk midplane. Hence, these young disks can already be ripe for the planet formation process to start. Multidimensional numerical models of disk formation that consider the coevolution of gas and dust including dust growth are important to improve our understanding of planet formation.
A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere
Authors: Færder Ø. H. , Nóbrega-Siverio D. , Carlsson M.
Published: January 2024

Context. Plasmoid-mediated reconnection plays a fundamental role in different solar atmospheric phenomena. Numerical reproduction of this process is therefore essential for developing robust solar models.

Aims. Our goal is to assess plasmoid-mediated reconnection across various numerical resistivity models in order to investigate how plasmoid numbers and reconnection rates depend on the Lundquist number.

Methods. We used the Bifrost code to drive magnetic reconnection in a 2D coronal fan-spine topology, carrying out a parametric study of several experiments with different numerical resolution and resistivity models. We employed three anomalous resistivity models: (1) the original hyper-diffusion from Bifrost, (2) a resistivity proportional to current density, and (3) a resistivity quadratically proportional to electron drift velocity. For comparisons, experiments with uniform resistivity were also run.

Results. Plasmoid-mediated reconnection is obtained in most of the experiments. With uniform resistivity, increasing the resolution reveals higher plasmoid frequency with weaker scaling to the Lundquist number, obtaining 7.9–12 plasmoids per minute for SL ∈ [1.8 × 104, 2.6 × 105] with a scaling of SL0.210 in the highest-resolution resistivity cases, transcending into Petschek reconnection in the high-SL limit (where the diffusive effects of the resistivity become small compared to the non-uniform viscosity) and Sweet-Parker reconnection in the low-SL limit. Anomalous resistivity leads to similar results even with lower resolution. The drift-velocity-dependent resistivity excellently reproduces Petschek reconnection for any Lundquist number, and similar results are seen with resistivity proportional to current-density though with slightly lower reconnection rates and plasmoid numbers. Among the different resistivity models applied on the given numerical resolution, the hyper-diffusion model reproduced plasmoid characteristics in closest resemblance to those obtained with uniform resistivity at a significantly higher resolution.
Dynamics of the β Pictoris planetary system and its falling evaporating bodies
Authors: Beust H. , Milli J. , Morbidelli A. , Lacour S. , Lagrange A.-M. , Chauvin G. , Bonnefoy M. , Wang J.
Published: January 2024

Context. For decades, the spectral variations of β Pictoris have been modelled as the result of the evaporation of exocomets close to the star, termed falling evaporating bodies (FEBs). Resonant perturbations by a hypothetical giant planet have been proposed to explain the dynamical origin of these stargrazers. The disk is now known to harbour two giant planets, β Pic b and c, orbiting the star at 9.9 and 2.7 au. While the former almost matches the planet formerly suspected, the recent discovery of the latter complicates the picture.

Aims. We first question the stability of the two-planet system. Then we investigate the dynamics of a disk of planetesimals orbiting the star together with both planets to check the validity of the FEB generation mechanism.

Methods. Symplectic N-body simulations are used to first determine which regions of the planetesimal disk are dynamically stable and which are not. Then we focus on regions where disk particles are able to reach high eccentricities, mainly thanks to resonant mechanisms.

Results. The first result is that the system is dynamically stable. Both planets may temporarily fall in 7:1 mean-motion resonance (MMR). Then, simulations with a disk of particles reveal that the whole region extending between ~l.5 au and ~25 au is unstable to planetary perturbations. However, a disk below 1.5 au survives, which appears to constitute an active source of FEBs via high-order MMRs with β Pic c. In this new picture, β Pic b acts as a distant perturber that helps sustain the whole process.

Conclusions. Our new simulations rule out the preceding FEB generation mechanism model, which placed their origin at around 4–5 au. Conversely, FEBs are likely to originate from a region much further in and related to MMRs with β Pic c. That mechanism also appears to last longer, as new planetesimals are able to continuously enter the MMRs and evolve towards the FEB state. Subsequently, the physical nature of the FEBs may differ from that previously thought, and presumably may not be icy.
Exsolution process in white dwarf stars
Authors: Camisassa Maria , Baiko Denis A. , Torres Santiago , Rebassa-Mansergas Alberto
Published: January 2024

Context. White dwarf stars are considered to be suitable cosmic laboratories for studying the physics of dense plasma. Furthermore, the use of white dwarf stars as cosmic clocks to date stellar populations and main sequence companions demands an appropriate understanding of the physics of white dwarfs in order to provide precise ages for these stars.

Aims. We aim to study exsolution in the interior of white dwarf stars, a process in which a crystallized ionic binary mixture separates into two solid solutions with different fractions of the constituents. Depending on the composition of the parent solid mixture, this process can release or absorb heat, thus leading to a delay or a speed-up of white dwarf cooling.

Methods. Relying on accurate phase diagrams for exsolution, we modeled this process in hydrogen(H)-rich white dwarfs with both carbon–oxygen (CO) and oxygen–neon (ONe) core composition, with masses ranging from 0.53 to 1.29 M⊙ and from 1.10 to 1.29 M⊙, respectively.

Results. Exsolution is a slow process that takes place at low luminosities (log(L/L⊙)≲ − 2.75) and effective temperatures (Teff ≲ 18 000 K) in white dwarfs. We find that exsolution begins at brighter luminosities in CO than in ONe white dwarfs of the same mass. Massive white dwarfs undergo exsolution at brighter luminosities than their lower-mass counterparts. The net effect of exsolution on white dwarf cooling times depends on the stellar mass and the exact chemical profile. For standard core chemical profiles and preferred assumptions regarding miscibility gap microphysics, the cooling delay can be as large as ∼0.35 Gyr at log(L/L⊙)∼ − 5. We neglect any chemical redistribution possibly associated with this process, which could lead to a further cooling delay. Although the chemical redistribution is known to accompany exsolution in binary solid mixtures on Earth, given the solid state of the matter, it is hard to model in a reliable way, and its effect may be postponed until very low luminosities.

Conclusions. Exsolution has a marginal effect on white dwarf cooling times and, accordingly, we find no white dwarf branches associated with it on the Gaia color–magnitude diagram. However, exsolution in massive white dwarfs can alter the faint end of the white dwarf luminosity function, thus impacting white dwarf cosmochronology.
Angular momentum transport near convective-core boundaries of Gamma Doradus stars
Authors: Moyano F. D. , Eggenberger P. , Salmon S. J. A. J.
Published: January 2024

Recent asteroseismic studies have revealed that the convective core ofγDoradus stars rotates faster than their radiative interior. We study the development of differential rotation near the convective core to test angular momentum transport processes that are typically adopted in stellar evolution models. Models that only include the advection of angular momentum by meridional circulation and shear instabilities cannot reproduce current rotational constraints, irrespective of the initial conditions. The latest formulation of internal magnetic fields based on the Tayler instability is indeed able to reproduce the internal rotation rate of post-main sequence stars; however, it appears too efficient during the main sequence and has thus been disfavoured. A less efficient version of the same transport process can simultaneously reproduce the rotation rate of the convective core, the rotation rate in radiative regions as probed by gravity-modes, and the surface rotational velocities ofγDoradus stars. Our work suggests that there are additional physical processes apart from internal magnetic fields at work in the stellar interiors of post-main sequence stars.
RETRACTED: Complementary information on the biology of Bactrian camels (Camelus bactrianus) in the Mangistau region of Kazakhstan
Authors: Bazarbayeva Zh. , Ilderbayev O. , Suleimenova A. , Dukenbayeva A. , Nurmukhambetova G. , Kabylbek A.
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Modern domestic solutions and software for Scandinavian logging in Russia under the new economic conditions
Authors: Svoykin F.V. , Zhuk K.D. , Svoykin V.F. , Borozna A.A. , Taraban M.V. , Kretinin V.I. , Uglova L.A.
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Impact of anthropogenic toxic substances on the antioxidant defense of Ceratophyllum demersum and Egeria densa
Authors: Glamazdin Igor , Kropova Yulia , Kartashev Valerii , Zavalishina Svetlana
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Microwave study of the effect of cold argon plasma on functional state of rat’s skin
Authors: Martusevich Andrew K. , Nazarov Vladimir V. , Surovegina Alexandra V. , Trunova Ekaterina A. , Fedotova Alexandra S.
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Automation of primary crushing control
Authors: Smolyaninov Andrey , Pocebneva Irina , Petukhov Yuri , Aleksandrovskiy Maxim
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Prospects for modelling the activities of tourist destinations
Authors: Hamidov Saidjon
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: On the history of the activity of scientific institutions and stations in growing new crop varieties in Uzbekistan
Authors: Haitov Jahongir
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Ecological approach to fish productivity preservation prospects of Rostov region water bodies
Authors: Neidorf Anna , Tkacheva Irina , Kokhanov Yuriy , Khetsuriani Elgudja , Dmitry Podoynitsyn , Hijnyakova Natalia
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Features of the course of compensated, subcompensated and decompensated intestinal dysbiosis in cats
Authors: Tresnitskiy Sergey , Lutsay Vladimir , Ananev Lev , Sysoeva Natalya , Rudenko Andrei , Rudenko Pavel
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Strategy of increasing protein production based on lupin and nano disintegrator technology
Authors: Ivanov Igor , Persiyanova Galina
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Modeling patterns of human well-being in the context of sustainable development and digital transformation
Authors: Makhosheva Salima , Kandrokova Marina , Shakhgiraev Ismail
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Characteristics of clinical course and comorbidity formation of arterial hypotension in farmer population
Authors: Mamasoliev Ne’matjon , Tursunov J.H. , Nazarova Gulchekhra , Suleymanova Nasibakhon , Ergashbaeva Dilrabokhon
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Analysis of mathematical methods for diagnosis of breast diseases
Authors: Sharipova Aziza , Faxriddinov Bekzod
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: ESG approach in the design of auto tourism facilities
Authors: Merenkov Artem , Grishkina Anna
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Ghrelin concentration before and after bariatric surgery
Authors: Galimov Oleg , Khanov Vladislav , Nasirova Kseniya , Galimov Dmitriy , Ibragimov Tel’man , Titova Tatyana , Titova Anastasiya , Ziangirov Robert , Sufiyarov Rinat
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Solving organizational problems using “X-TRIZ” technique: empirical study
Authors: Al-Ali Abdulsattar , Shenshinov Yuri
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Transformation of mechanisms of the university first-year students’ social adaptation: mathematical analysis tools
Authors: Ivashova Valentina , Gulyak Ivan , Nazarenko Anton , Zhukova Victoria , Rodionova Valentina , Mogilevskaya Galina
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Sport orientation and stages of selection in multiyear training in academic rowing in the context of pro-environmental behavior
Authors: Bayer Elena , Arakelyan Samvel , Aivazova Elena
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Digital didactics in the context of Bachelor’s education
Authors: Zakharova Natalya , Lopatchenko Таtiana
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Targeting in management of sustainable innovative development for industrial enterprises
Authors: Zharov Vladimir
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Technical progress and its issues
Authors: Bataeva Patimat , Valeev Sergey , Bagov Artur
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Techniques for the formation of the natural and ecological framework of riverine cities (on the example of Rostov-on-Don)
Authors: Vorob’yova A.M.
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Prospects for utilizing secondary resources in the construction of facilities for various purposes
Authors: Korchagin Alexey , Miller Viktor , Bolgov Vladimir
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Studying the effectiveness of comprehensive wastewater treatment
Authors: Izbullaeva Malika , Amonov Mukhtor , Jalilov Sherali
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: Development of an combined energy complex consisting of a micro-hydroelectric power plant and a solar photoelectric plant for the conditions of Uzbekistan
Authors: Yusupova Feruza , Sultanov Nomomjon
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
RETRACTED: The method of complex biological water treatment in aquaponic recirculation systems
Authors: Fedorova Valeria , Shvydchenko Sergey , Dubovik Irina , Shvydchenko Darina
Published: January 2024

See the retraction notice BIO Web of Conferences 84, 00001 (2024), https://doi.org/10.1051/bioconf/20248400001
Optimisation of Torque Ripples in Permanent Magnet Synchronous Motor using Hysteresis Current Controller
Authors: Pala Prasad Reddy Mule , Siva Prasad Syamala , Venu Gopal Talla , Madhusudhana Rao Gurrala , Sreeramula Reddy Nandyala
Published: January 2024

This paper’s primary goal is to investigate and analyze how a particular PWM technique enhances the performance of PMSM drives. The objective of the analysis is to reduce torque ripples, which are fluctuations or variations in the motor’s torque output. Reducing these torque ripples involves combining the Hysteresis Control and Space Vector Pulse Width Modulation (SVPWM) techniques. Hysteresis Control is a method that compares the actual value of a parameter (in this case, torque) with a reference value and takes appropriate control actions based on the comparison. SVPWM, on the other hand, is a sophisticated technique used for generating pulse width modulation signals that can control the motor precisely and efficiently. The research findings suggest that combining the Hysteresis Control technique with SVPWM in the PMSM motor drive makes the system more effective and efficient. This combination likely reduces torque ripples, leading to a smoother motor operation. Using both techniques together probably enhances the precision and stability of the motor control system.
Review on the Electric Spring Connected to the Renewable Energy System to Minimize Harmonics and Voltage Profile Enhancement
Authors: Rao P. Nageswara , Prakash S. Jaya , Chaitanya S. , Rajeev K.
Published: January 2024

The emerging smart grid technology known as Electric Spring (ES) has been employed previously to maintain voltage and power stability in renewable energy-based grids that are minimally regulated or self-contained. This study thoroughly investigated the foundational theories, modeling approaches, practical uses, and restrictions associated with Electric Springs by analyzing existing Scholarly works in this domain Electric Springs implement a direct power control approach. solution for the next-generation single-phase Systems, addressing the limitations of current ES control methods. This solution aims to improve power management in microgrids, where integrating renewable energy sources (RESs) poses challenges due to the unpredictable power output. The challenge involves managing two aspects: the variable Power consumed by ES and the power fed into the grid. The suggested straightforward and accurate signal manipulation method, namely, ANN-based Electric Spring (ES), is set to be deployed. This technique can adeptly manage these aspects in both stable conditions and during transitions in Renewable Energy Sources (RES).
Flexible output pattern high-power pulse generator
Authors: Radhika G. , Sashidhar K. , Sai Krishna P. Aravinda , Avaneesh C.
Published: January 2024

Day by day, the need for renewable fuel has increased to reduce the usage of non-renewable fuels and also to provide adequate fuel for vehicle use worldwide. Organic fuels that can be derived from different sources are renewable fuels, of which oil extracted from algae cells can also be used as a biofuel. Algae oil extraction can be achieved by applying a Pulsed Electric Field across the algae cell to rupture its membrane and to remove oil. A Pulse Generator, capable of carrying out this operation, although in existence, has some drawbacks including lack of versatility, performance and reliability, etc. Pulse generators can also be used for many other purposes, including cancer cell ablation, water treatment, thunder and lightning safety testing of electrical equipment, lasers, radar systems, military, etc. Hence a Pulse generator capable of generating the necessary Pulse patterns, maintaining a reasonable efficiency and performance, including features such as versatility, simple input voltage stepping, high switching frequency etc. The design of a novel solid-state-based topology with the required features is considered to be the main objective of this work. In this paper, we aim to present the design and simulation of the proposed circuit, along with some results obtained.
Enhancing Sentiment Analysis Accuracy by Optimizing Hyperparameters of SVM and Logistic Regression Models
Authors: Siri Yellu , Afroz Suhail , Usha Rani Rella
Published: January 2024

The Analysis of Sentiments expressed on Twitter is a widely practiced application of Natural Language Processing (NLP) and Artificial Intelligence (AI). This process involves examining tweets to determine the emotional tone conveyed within the message. AI-based approaches are employed in Twitter sentiment analysis, typically following these steps: Data Collection, Data Preprocessing, and Sentiment Analysis, where AI techniques like Support Vector Machines (SVM) and Logistic Regression are utilized to categorize tweets into positive, negative, or neutral sentiments. Twitter data is a valuable source of information, serving diverse purposes such as real-time updates, user feedback, brand monitoring, market research, digital marketing, and political analysis. The Twitter API (Application Programming Interface) provides developers with tools and functionalities to access and interact with Twitter data, including tweets, user profiles, and timelines, enabling a wide range of applications and services. However, Twitter sentiment analysis presents challenges such as handling sarcasm, irony, colloquial language, and coping with the sheer volume and rapid flow of Twitter data. Nevertheless, with effective preprocessing techniques and AI methods, Twitter sentiment analysis can yield valuable insights into public opinion on various topics.
The physics of gain relevant to inertial fusion energy target designs
Authors: Trickey W. , Goncharov V. N. , Betti R. , Campbell E. M. , Collins T. J. B. , Follett R. K.
Published: January 2024

In inertial confinement fusion, pellets of deuterium tritium fuel are compressed and heated to the conditions where they undergo fusion and release energy. The target gain (ratio of energy released from the fusion reactions to the energy in the drive source) is a key parameter in determining the power flow and economics of an inertial fusion energy (IFE) power plant. In this study, the physics of gain is explored for laser-direct-drive targets with driver energy at the megajoule scale. This analysis is performed with the assumption of next-generation laser technologies that are expected to increase convergent drive pressures to over 200 Mbar. This is possible with the addition of bandwidth to the laser spectrum and by employing focal-spot zooming. Simple physics arguments are used to derive scaling laws that describe target gain as a function of laser energy, adiabat, ablation pressure, and implosion velocity. Scaling laws are found for the unablated mass, ablation pressure, areal density, implosion velocity, and in-flight aspect ratio. Those scaling laws are then used to explore the design space for IFE targets.
Voltage-controlled cryogenic Boolean logic gates based on ferroelectric SQUID and heater cryotron
Authors: Alam Shamiul , Hossain Md Shafayat , Ni Kai , Narayanan Vijaykrishnan , Aziz Ahmedullah
Published: January 2024

The recent progress in quantum computing and space exploration led to a surge in interest in cryogenic electronics. Superconducting devices such as Josephson junction, Josephson field effect transistor, cryotron, and superconducting quantum interference device (SQUID) are traditionally used to build cryogenic logic gates. However, due to the superconducting nature, gate-voltage-based control of these devices is extremely difficult. Even more challenging is to cascade the logic gates because most of these devices require current bias for their operation. Therefore, these devices are not as convenient as the semiconducting transistors to design logic gates. Here, to overcome these challenges, we propose a ferroelectric SQUID (FeSQUID) based voltage-controlled logic gates. FeSQUID exhibits two different critical current levels for two different voltage-switchable polarization states of the ferroelectric. We utilize the polarization-dependent (hence, voltage-controllable) superconducting to resistive switching of FeSQUID to design Boolean logic gates such as Copy, NOT, AND, and OR gates. The operations of these gates are verified using a Verilog-A-based compact model of FeSQUID. Finally, to demonstrate the fanning out capability of FeSQUID-based logic family, we simulate a two-input XOR gate using FeSQUID-based NOT, AND, and OR gates. Together with the ongoing progress on FeSQUID-based non-volatile memory, our designed FeSQUID-based logic family will enable all FeSQUID-based cryogenic computer, ensuring minimum mismatch between logic and memory blocks in terms of speed, power consumption, and fabrication process.
Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X
Authors: Ponomarenko S. , Moseev D. , Stange T. , Krier L. , Stordiau P. , Braune H. , Gantenbein G. , Jelonnek J. , Kuleshov A. , Laqua H. P. , Lechte C. , Marsen S. , Nielsen S. K. , Oosterbeek J. W. , Plaum B. , Ragona R. , Rasmussen J. , Ruess T. , Salewski M. , Thumm M. , Zimmermann J. ,   W7-X Team
Published: January 2024

In this paper, we present the design and commissioning results of the upgraded collective Thomson scattering diagnostic at the Wendelstein 7-X stellarator. The diagnostic has a new radiometer designed to operate between the second and third harmonics of the electron cyclotron emission from the plasma at 171–177 GHz, where the emission background has a minimum and is of order 10–100 eV. It allows us to receive the scattered electromagnetic field with a significantly improved signal-to-noise ratio and extends the set of possible scattering geometries compared to the case of the original instrument operated at 140 GHz. The elements of the diagnostic are a narrowband notch filter and a frequency stabilized probing gyrotron that will allow measuring scattered radiation spectra very close to the probing frequency. Here, we characterize the microwave components applied to the radiometer and demonstrate the performance of the complete system that was achieved during the latest experimental campaign, OP2.1.
Impact of tracer particles on the electrolytic growth of hydrogen bubbles
Authors: Han Yifan , Bashkatov Aleksandr , Huang Mengyuan , Eckert Kerstin , Mutschke Gerd
Published: January 2024

The thermocapillary effect at gas bubbles growing at micro-electrodes seems well understood. However, the interfacial flow measured in the upper bubble part decays faster than found in first simulations by Massing et al. [“Thermocapillary convection during hydrogen evolution at microelectrodes,” Electrochim. Acta 297, 929 (2019)]. Recently, Meulenbroek et al. attributed the origin of the difference to the influence of surfactants being present in the electrolyte [“Competing Marangoni effects from a stagnant cap on the interface of a hydrogen bubble attached to a microelectrode,” Electrochim. Acta 385, 138298 (2021)]. Surprisingly, the presence of tracer particles added to the electrolyte for measuring its flow was not yet considered. Our recent experiments reveal that varying the small amount of tracer particles added influences the bubble shape, its dynamics, and also the electrolyte flow nearby. We therefore present a model to describe the particle attraction to and the particle dynamics at the bubble interface, which allows us to quantify the impact. Corresponding simulations are validated against measurements for different bulk particle concentrations and show a good agreement of the tangential velocity profile at the bubble interface caused by thermo- and solutocapillary effects. Depending on the particle concentration, parts of the upper bubble interface are found to become stagnant. The results allow a deeper insight into the complex phenomena of electrolytic gas evolution and further put attention to a careful application of particle-based measurement techniques in gas–liquid systems.
Mid-infrared spectroscopic thermotransmittance measurements in dielectric materials for thermal imaging
Authors: Bourges C. , Chevalier S. , Maire J. , Sommier A. , Pradere C. , Dilhaire S.
Published: January 2024

Thermal considerations affect the performance of most microsystems. Although surface techniques can give information on the thermal properties within the material or about buried heat sources and defects, mapping temperature and thermal properties in three dimension (3D) is critical and has not been addressed yet. Infrared thermography, commonly used for opaque materials, is not adapted to semi-transparent samples such as microfluidic chips or semiconductor materials in the infrared range. This work aims at answering these needs by using the variations of transmittance with temperature to obtain information on the temperature within the thickness of the sample. We use a tunable mid-infrared light source combined with an infrared camera to measure these variations of transmittance in a glass wafer. We couple this technique with a thermal model to extract the thermotransmittance coefficient—the coefficient of temperature variation of the transmittance. We then introduce a semiempirical model based on Lorentz oscillators to estimate the temperature-dependent optical properties of our sample in the mid-IR spectral range. Combined with the measurement, this paper reports the spectroscopic behavior of the thermotransmittance coefficient in the mid-IR range and a way to predict it.
Effect of kerosene injection states on mixing and combustion characteristics in supersonic combustor at high equivalent ratio
Authors: Liu Xu , Li Peibo , Li Fei , Wang Chao , Yang Xiaolong , Wang Hongbo , Sun Mingbo , Yang Yixin , Xiong Dapeng , Wang Yanan
Published: January 2024

Previous studies have found that the difference in combustion characteristics of gaseous and liquid kerosene injection in supersonic combustor is sensitive to the equivalent ratio. In this paper, the previous work is extended to a high equivalent ratio to gain a deeper understanding of the effect of injection states on combustion performance via numerical computation. The simulation results match well with the experiments and demonstrate that due to the different jet structures, the cavity shear layer of liquid injection penetrates deeply into the cavity, forming two recirculation zones therein. As a result, the majority of droplets enter the cavity and exist at a low streamwise velocity, which is favorable to droplet vaporization and combustion. Therefore, when the liquid fuel is injected at a high equivalent ratio, the fuel residence time increases, the droplet evaporation distance decreases, and the fuel vapor accumulates in the cavity. Compared to the gaseous injection with the same equivalent ratio, the liquid injection exhibits similar mixing efficiency in the cavity but slightly higher mixing efficiency in downstream divergent sections. This unique fuel distribution causes the liquid injection to have a higher combustion efficiency than that of the gaseous injection. The weak advantage in mixing and combustion makes the liquid injection capable of compensating for the effects of the fuel atomization and evaporation on combustion performance. As a result, the combustion structure and static pressure distribution of liquid injection with the high equivalent ratio is similar to those of the gaseous injection.
A comparison of QTP functionals against coupled-cluster methods for EAs of small organic molecules
Authors: Pavlicek Abigail , Windom Zachary W. , Perera Ajith , Bartlett Rodney J.
Published: January 2024

EA-EOM-CCSD electron affinities and LUMO energies of various Kohn–Sham density functional theory (DFT) methods are calculated for an a priori IP benchmark set of 64 small, closed-shell molecules. The purpose of these calculations was to investigate whether the QTP KS-DFT functionals can emulate EA-EOM-CC with only a mean-field approximation. We show that the accuracy of DFT—relative to CCSD—improves significantly when elements of correlated orbital theory are introduced into the parameterization to define the QTP family of functionals. In particular, QTP(02), which has only a single range separation parameter, provides results accurate to a MAD of <0.15 eV for the whole set of 64 molecules compared to EA-EOM-CCSD, far exceeding the results from the non-QTP family of density functionals.
A study on dynamics of shock-accelerated forward-facing triangular bubbles at different Atwood numbers
Authors: Kundu Abhishek , Thangadurai Murugan , Biswas Gautam
Published: January 2024

The complexity of flow physics and the associated hydrodynamic instability arising out of interactions of a shock wave with forward and backward-facing triangular interfaces drew the attention of researchers around the globe. In earlier studies, many researchers focused on the formation of different wave patterns, the development of instabilities at the interface, and the flow morphology during the initial phase of shock wave interacting with light and heavier bubbles. However, limited studies are available in the literature on the interaction of shock with a polygonal interface. Furthermore, it is difficult to capture the complex flow physics of a polygonal interface accelerated by shock waves at later time instants. In the present study, the dynamics of shock-accelerated forward-facing triangular interface containing various gases, namely, sulfur hexafluoride, refrigerant-22, argon, neon, and helium, are examined numerically for a longer time duration for a shock Mach number of 1.21. The simulations were performed by solving two-dimensional Euler equations using a low-dissipative advection upstream splitting method algorithm coupled with a derived ninth-order upwind scheme and a four-stage third-order Runge–Kutta scheme. The numerical results demonstrated the influence of the Atwood number on vorticity generation, bubble deformation, mixing, and the development of Kelvin Helmholtz instabilities on the bubble interface up to long instants, which are not available in the literature. The Fourier spectra of the streamwise kinetic energy showed the distribution of energy in the larger and smaller scale vortical structures.
Magnetic nanoparticle interaction with a hydrogel in an oscillating magnetic field
Authors: Ahmadinejad Mehrdad , Marshall Jeffrey S.
Published: January 2024

A study was conducted of the effect of superparamagnetic nanoparticles on a hydrogel in the presence of an oscillating magnetic field directed tangent to the hydrogel surface. The oscillating magnetic field causes the particles to oscillate laterally in the hydrogel, with some of the particles adhering to the hydrogel matrix and other particles moving freely through the hydrogel pore spaces. The analysis was performed for a three-phase matrix-water-particles model, in which the solvent (water) and hydrogel matrix are interacting continua and the particles are a discrete phase. The study examined the effect of fluid elasticity on wave propagation due to the no-slip boundary condition acting under the transversely oscillating magnetic field. A memory effect within the fluid results in a deviation of the minimum and maximum shear rates observed in one half of the oscillation period from those observed in the other half of the oscillation period. The behavior of the hydrogel with different values of the governing dimensionless parameters was assessed. The matrix Reynolds number, the Deborah number, and the ratio of matrix relaxation to retardation times were all observed to have significant influence on the hydrogel viscoelastic response and on the wave propagation within the hydrogel. The phase difference between the water and matrix oscillations is strongly influenced by the phase interaction force coefficient, the Deborah number, and the ratio of free to captured particles. The system is found to approach an asymptotic state at a high Deborah number, which is independent of the value of the Deborah number.
Experimental study of viscous effects on long-duration sloshing characteristics under surge excitations
Authors: He Wei , Tang Lian , Lin Pengzhi
Published: January 2024

This study aims to investigate the initial transient effects and the final steady-state sloshing characteristics under long-duration surge excitations experimentally. Liquids with different viscosity are applied in the sloshing experiments. The image recognition method is innovatively employed to accurately capture the free surface elevation in these experiments. The viscous effects are found to play a crucial role in altering the damping of the transient mode associated with its natural frequencies and the establishment of the steady-state mode related to the excitation frequency. The mechanism of viscous effects on energy dissipation and transferring is further revealed by Fast Fourier transform and wavelet transform. Then, the damping rates of liquid sloshing with different viscosities are quantitatively measured and analyzed, with reference to the early theories. It is found that with the use of the damping coefficient derived from the experimental data, we are able to describe the long-term evolution of sloshing using the potential flow theory corrected by a damping term, representing the viscous effects of a particular viscous liquid. The accuracy and applicability of this approach is further discussed in this paper.
Characterization of a LaB6 tip as a thermionically enhanced photoemitter
Authors: Guo Xuefei , Chaudhuri Dipanjan , Bielinski Nina , Chen Jin , Kim Soyeun , Chiang Tai C. , Mahmood Fahad , Soares Julio A. N. T. , Karkare Siddharth , Abbamonte Peter
Published: January 2024

There is a widespread interest in time-resolved electron spectroscopies such as ultrafast electron diffraction, ultrafast electron microscopy, and ultrafast electron energy loss spectroscopy. These techniques require pulsed electron beams with both high current and brightness. LaB6 is commonly used as a thermionic emitter because of its low work function and high electron yield. However, its use as a pulsed photocathode has not been widely explored. Here, we present measurements of the electron yield from a LaB6 filament exposed to 392 nm UV ultrafast laser pulses under a wide range of filament temperatures. We find that sample heating strongly enhances photoelectron yield, an effect known as thermionically enhanced photoemission. However, it also creates potentially undesirable, continuous thermionic background. We conclude that the ideal optimal operating conditions strongly depend on the type of measurement and require defining and quantifying an appropriate figure of merit.
Determining internal coordinate sets for optimal representation of molecular vibration
Authors: Oenen Kemal , Dinu Dennis F. , Liedl Klaus R.
Published: January 2024

Arising from the harmonic approximation in solving the vibrational Schrödinger equation, normal modes dissect molecular vibrations into distinct degrees of freedom. Normal modes are widely used as they give rise to descriptive vibrational notations and are convenient for expanding anharmonic potential energy surfaces as an alternative to higher-order Taylor series representations. Usually, normal modes are expressed in Cartesian coordinates, which bears drawbacks that can be overcome by switching to internal coordinates. Considering vibrational notations, normal modes with delocalized characters are difficult to denote, but internal coordinates offer a route to clearer notations. Based on the Hessian, normal mode decomposition schemes for a given set of internal coordinates can describe a normal mode by its contributions from internal coordinates. However, choosing a set of internal coordinates is not straightforward. While the Hessian provides unique sets of normal modes, various internal coordinate sets are possible for a given system. In the present work, we employ a normal mode decomposition scheme to choose an optimal set. Therefore, we screen reasonable sets based on topology and symmetry considerations and rely on a metric that minimizes coupling between internal coordinates. Ultimately, the Nomodeco toolkit presented here generates internal coordinate sets to find an optimal set for representing molecular vibrations. The resulting contribution tables can be used to clarify vibrational notations. We test our scheme on small to mid-sized molecules, showing how the space of definable internal coordinate sets can significantly be reduced.
The influence of thermal dispersion on the initiation of convective instability in Prats flow through a low permeability porous medium
Authors: Dubey Rashmi , Chetteti Ramreddy
Published: January 2024

This study investigates the effect of thermal dispersion on the onset of convective thermal instability in a fluid-saturated porous medium. A horizontal throughflow is considered along the layer, which is bounded by two uniformly heated horizontal rigid impermeable walls from above and below. The two walls are maintained at a constant temperature gradient, which is responsible for the buoyancy to occur and thus making the convection happen. Considering thermal dispersion, we have examined how it affects the natural convective instability occurring due to the thermal buoyancy. This paper proposes an entirely new perspective on the accountability of thermal dispersion in the convective instability. The consideration of Prats flow causes the instability in monotonic and oscillatory modes, where in some of the cases, the convection initiates in the oscillatory modes.
Pixel-dependent laser-induced fluorescence method for determining thin liquid film thickness distribution
Authors: Chen Hongbai , Wang Wenzhong , Ge Xiangyu , Liang He
Published: January 2024

Thin liquid films on free surfaces or inside restricted spaces are widely encountered and can have significant effects in heat transfer, coating, biofilm growth, and lubrication. The thickness and distribution of these thin liquid films are important determinants of performance, but cannot easily be measured accurately. This paper presents a methodological study on determining the thickness of thin liquid films by means of laser-induced fluorescence. A model of fluorescence imaging and measurement is established based on the fluorescence energy transmission. A novel pixel-dependent laser-induced fluorescence method is then proposed and compared with commonly used methods using experimental test results. The accuracy and precision of the measurements are discussed in detail. It is found that the measurement performance is greatly influenced by the nonlinearity, heterogeneity, and random noise of the optical system and imaging technique. The proposed pixel-dependent laser-induced fluorescence method effectively eliminates or ameliorates the effects of these factors and enhances the measuring accuracy.
Silicon implantation and annealing in β-Ga2O3: Role of ambient, temperature, and time
Authors: Gann Katie R. , Pieczulewski Naomi , Gorsak Cameron A. , Heinselman Karen , Asel Thaddeus J. , Noesges Brenton A. , Smith Kathleen T. , Dryden Daniel M. , Xing Huili Grace , Nair Hari P. , Muller David A. , Thompson Michael O.
Published: January 2024

Optimizing thermal anneals of Si-implanted β-Ga2O3 is critical for low resistance contacts and selective area doping. We report the impact of annealing ambient, temperature, and time on the activation of room temperature ion-implanted Si in β-Ga2O3 at concentrations from 5 × 1018 to 1 × 1020 cm−3, demonstrating full activation (>80% activation, mobilities >70 cm2/V s) with contact resistances below 0.29 Ω mm. Homoepitaxial β-Ga2O3 films, grown by plasma-assisted molecular beam epitaxy on Fe-doped (010) substrates, were implanted at multiple energies to yield 100 nm box profiles of 5 × 1018, 5 × 1019, and 1 × 1020 cm−3. Anneals were performed in an ultra-high vacuum-compatible quartz furnace at 1 bar with well-controlled gas compositions. To maintain β-Ga2O3 stability, pO2 must be greater than 10−9 bar. Anneals up to pO2 = 1 bar achieve full activation at 5 × 1018 cm−3, while 5 × 1019 cm−3 must be annealed with pO2 ≤ 10−4 bar, and 1 × 1020 cm−3 requires pO2 < 10−6 bar. Water vapor prevents activation and must be maintained below 10−8 bar. Activation is achieved for anneal temperatures as low as 850 °C with mobility increasing with anneal temperatures up to 1050 °C, though Si diffusion has been reported above 950 °C. At 950 °C, activation is maximized between 5 and 20 min with longer times resulting in decreased carrier activation (over-annealing). This over-annealing is significant for concentrations above 5 × 1019 cm−3 and occurs rapidly at 1 × 1020 cm−3. Rutherford backscattering spectrometry (channeling) suggests that damage recovery is seeded from remnant aligned β-Ga2O3 that remains after implantation; this conclusion is also supported by scanning transmission electron microscopy showing retention of the β-phase with inclusions that resemble the γ-phase.