bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive inverse control for trajectory tracking with dead‐zone nonlinearity under cyberattacks
Authors: Sabahi Farnaz
Published: December 2024

Control systems rely heavily on the accuracy and reliability of sensor data; however, the integrity of these data can be compromised through spoofing attacks, leading to significant modelling errors that can render control impractical. In addition, centralized control poses a significant threat to system security. To address these issues, a distributed framework is suggested for a discrete‐time nonlinear system that encounters unknown dead‐zones at its input. The framework uses the inherent resilience of a decentralized peer‐to‐peer network to secure information exchange, eliminating the need for prior knowledge of system dynamics or potential attacks. The proposed framework performs two complex tasks: identifying the nonlinear system and dealing with the unknown nonlinearity at the input in the form of a dead‐zone. An adaptive dead‐zone inverse is used to handle the unknown nonlinearity at the input in the form of a dead‐zone and integrate blockchain technology to secure communication between components. The blockchain component ensures tamper‐proof data transmission and resistance to cyberattacks, providing both detection and defence mechanisms without prior knowledge of system dynamics or potential attacks. The actuator and plant components are matched and synchronized using a private network with static nodes, ensuring deterministic and well‐coordinated communication. Simulation results demonstrate that the proposed framework both with and without blockchain integration, maintains stability and outperforms traditional methods in terms of robustness and accuracy, even when all parts of the framework are adjusted in response to attacks.
Study on desorption mechanism and thermal stability of OTS coating as an anti‐relaxation material
Authors: Liu Guodong , He Xinxin , Liu Xiaoya , Ma Donghui , Tang Jun , Ma Zongmin , Li Yanjun , Liu Jun
Published: December 2024

This research explores the desorption mechanism and thermal stability of octadecyltrichlorosilane (OTS, CH3(CH2)17SiCl3) coating on quartz slides and in alkali‐metal vapour cells. The morphological thermal‐changes, energy dissipation diversity, and anti‐relaxation characteristic of OTS coatings before and after exposure to Cs atoms by Fourier transform infrared spectroscopy, water contact angle measurement, atomic force microscopy imaging, collision energy dissipation analysis, and free induction decay of Cs atoms are measured systematically. The results show that the OTS coatings exhibit the best thermal stability under the specific process conditions, and the homogeneous and dense structure makes the adsorption of alkali‐metal atoms more stable, which effectively reduces surface energy dissipation and prolongs the relaxation time of Cs atoms. The study provides certain reference for efficient anti‐relaxation coating fabrication and coated cell application.
Estimer les infections à Eimeria spp. en atelier d’engraissement d’agneaux à l’aide d’analyses coprologiques de mélange et de litière
Authors: Bordes Léa , Grisez Christelle , Droillard Nais , Dumas Elisa , Corbière Fabien , Jacquiet Philippe
Published: December 2024

La coccidiose ovine est une problématique importante dans les systèmes d’engraissement. Son contrôle repose sur l’utilisation d’anticoccidiens, à administrer après diagnostic selon la nouvelle réglementation européenne. Or, les méthodes de diagnostic individuelles sont coûteuses et chronophages. Dans cette étude, nous avons développé l’utilisation d’analyses coprologiques de mélange de 5 prélèvements d’animaux, ainsi que des analyses coprologiques sur litière souillée. L’essai a été réalisé dans un atelier d’engraissement, suivi de manière hebdomadaire durant presque deux mois, sur 2 loges, en prélevant individuellement 50 agneaux par loge et trois échantillons de litière par loge. Les trois méthodes de diagnostic (individuelles, de mélange de 5 échantillons individuels et d’échantillons de litière) ont présenté de fortes corrélations en termes d’intensité d’excrétion des oocystes de coccidies, mais également dans les proportions d’espèces pathogènes. Ces résultats démontrent qu’il est possible de suivre les infections des animaux par les coccidies avec ces deux nouvelles méthodes d’échantillonnage et d’avoir une représentation fiable de la prévalence de l’infection, mais également de son intensité au sein d’un lot d’animaux. Ainsi, ces deux méthodes permettent d’alléger le coût du diagnostic, mais également de réduire le temps passé sur le chantier de prélèvement et au laboratoire.
Les arthrites chez les bovins
Authors: Robcis Rodolphe
Published: December 2024

Les arthrites chez les bovins sont une affection courante en médecine vétérinaire rurale. En première intention, le traitement repose sur une antibiothérapie ciblée et adaptée, combiné à une prise en charge de la douleur au moyen d’anti-inflammatoires, voire d’opioïdes. En cas d’échec, le recours à la chirurgie est souhaitable. Trois options sont possibles (par difficulté croissante) : lavage articulaire, arthrotomie et arthrodèse. Une bonne connaissance de ces trois techniques chirurgicales permet une bonne application sur le terrain avec des bons résultats.
The Rise, Fall, and Readjustment of Telehealth: Effect of COVID-19 on its Use in an Academic Health Clinic
Authors: Shammout Ali , Daneshvari Berry Shamsi , Ziemkowski Peter , Kroth Phillip
Published: December 2024

Background:
The COVID pandemic accelerated the adoption of telehealth. Long-term implications for continued telehealth use on a large scale in primary care are still emerging, and the key to this understanding is how telehealth adoption impacts the delivery of health care.
Objectives:
Our objective was to quantify how telehealth adoption during the pandemic impacted patients’ access to healthcare and the usage patterns of different access modalities (in-office, audio, and video).

Methods:
This study analyzed two years of de-identified EHR data from the ambulatory clinics at a Midwest medical school from 2020 and 2021. We focused on patient demographics, primary diagnoses, and patient preferences for receiving healthcare throughout the COVID-19 pandemic.
Results:
Of the 105,362 patient visits analyzed across in-office, audio, and video visits, demographic data varied by gender, age, and racial composition. During the early pandemic, telehealth usage peaked in April 2020, with audio and video visits accounting for 45.8% and 18.07% of the total visits, respectively. These rates declined to averages of 12.47% and 3.58%, respectively, over the following months. Primary diagnoses during telehealth visits are often related to COVID-19 exposure or mental health or behavioral issues. Lastly, statistically significant associations exist between the visit modality and primary diagnoses.
Discussion:
The COVID-19 pandemic initially saw a surge in audio telehealth visits; however, as safety measures were established, the mix of visit modalities returned to pre-lockdown levels. Video and audio telehealth maintained increased usage relative to pre-pandemic levels, potentially owing to increased awareness of the technology as a means for accessing healthcare and a learning curve associated with adoption. Patients preferred remote care during high COVID transmission. Video telehealth has shown significant associations with psychiatric, behavioral, and neurodevelopmental diagnoses. Disparities in video telehealth use among racial groups have highlighted potential access issues.
Critical parameters of pure 2H−NbSe2 crystals and those intercalated with TCNQ molecules
Authors: Obolenskii M. A. , Chashka Kh. B. , Beletskii V. I. , Balla D. D. , Starodub V. A.
Published: December 2024

We have studied experimentally the anisotropy of the upper critical field Hc2 as a function of the angle θ between the magnetic field and the plane of the layers, as well as the properties of the transition to the resistive state in a magnetic field for pure 2H−NbSe2 crystals and for ones intercalated with TCNQ molecules. Intercalation leads to a lowering of the critical temperature, an increase in the anisotropy of the upper critical field, and the appearance of a steplike structure of the superconducting transition.
Creep in solid hydrogen at the unsteady stage
Authors: Alekseeva L. A. , Litvin O. V. , Krupskii I. N.
Published: December 2024

A study was made of unsteady creep in normal hydrogen (75% ortho-hydrogen) over a wide temperature range, namely from 1.8 to 12 °K, and also in parahydrogen with the orthohydrogen content reduced to 0.2% at helium temperatures. It has been found that the strain of solid hydrogen varies in time according to two different laws, depending on the temperature of the test specimens and on the concentration of deuterium impurities. In the range of helium temperatures, where creep in n-H2 is logarithmic, no temperature dependence has been found. In pure parahydrogen down to 1.8 °K creep is associated with climbing of dislocations. The role of quantum effects is also considered.
Uhf absorption of electrons above a helium film
Authors: Karamushko V. I. , Kovdrya Yu. Z. , Mende F. F. , Nikolaenko V. A.
Published: December 2024

The uhf absorption of electrons localized above a helium film on a dielectric surface is measured at a frequency of ∼ 10 GHz. Absorption was determined from the change in the Q of a superconductive resonator when a dielectric insert located in the resonator and wetted by the helium film was charged with electrons. Electron mobility above the helium film is determined and it is shown that the value of this mobility is apparently determined by localization of electrons on substrate defects. A new type of bound surface state is recorded – electrons on the helium film, localized above positive ions bound to the dielectric substrate.
Quantum oscillation effects in cylindrical conductors
Authors: Nedorezov S. S. , Avad-Alla M. S.
Published: December 2024

The energy spectrum and the density of electron states in a cylindrical conductor of radius R located in a longitudinal magnetic field H are analyzed. It is assumed that the reflection of the electrons by the sample boundary is specular. It is found that quantum oscillations similar to the Kosevich–Lifshitz oscillations for electrons in a plate occur in fields for which the radius of the Larmor orbit rH>R.
Transverse focusing of electrons in a metal with a superconducting coating
Authors: Kolesnichenko Yu. A.
Published: December 2024

Transverse focusing of electrons (EF) in a normal metal, in which there is a region with a superconducting coating between the emitter and collector, is examined theoretically. It is shown that Andreev reflection of charged carriers leads to the appearance of lines of EF with opposite signs. The amplitude of the focusing peaks carries information on the probability of Andreev reflection of electron and hole excitations at the boundary between the normal and superconducting phases and its temperature dependence.
Temperature dependence of the yield stress of solid hydrogen
Authors: Alekseeva L. A. , Litvin O. V. , Krupskii I. N.
Published: December 2024

The plastic properties of solid normal hydrogen (orthomodification content 75%) were studied over a wide temperature range 2–12 °K using stepped loading of specimens. It was found that when the temperature varies from 8 to 12 K, the yield stress σ0 decreases by almost an order of magnitude. For T < 8 °K, σ0 is practically independent of temperature. The role of quantum effects is discussed.
Adiabatic effects in surface electron scattering: a new boundary condition
Authors: Kaner É. A. , Krokhin A. A. , Makarov N. M. , Yampol’skii V. A.
Published: December 2024

We obtain a new electron–surface collision integral, taking into account conservation of the adiabatic invariant in a system with periodic motion along one axis. This integral is used to calculate the frequency of surface relaxation and the impedance of a metal with a rough bounary in a parallel magnetic field. We find the dependence of electromagnetic absorption on frequency, on magnetic field, and on the stochastic properties of the boundary in a limiting case of strong correlation between subsequent collisions of grazing electrons. It is shown that at low temperatures the mechanism of surface scattering can compete with the mechanism of bulk scattering.
Superconducting transition and electrical current in a crystal containing a screw dislocation
Authors: Dubrovskii I. M.
Published: December 2024

Development of a superconducting filament near a screw dislocation, transition into the superconducting state of a crystal containing a screw dislocation, and the superconducting current distribution in a crystal containing such a dislocation are considered using the Ginzburg–Landau and London equations. It is shown that conditions for development of the superconducting filament near the screw dislocation depend significantly on the behavior of the order parameter in the dislocation core. It is noted that appearance of the superconducting filament is not a true phase transition, which in fact takes place in a three-dimensional frame of such filaments. It is shown that passage of a current along the screw dislocation leads to the development of a related turbulent filament, which does not disappear when the transport current is switched off.
Electron scattering in metals with a multiply connected Fermi surface in a quantizing magnetic field
Authors: Tarasov Yu. V. , Usatenko O. V.
Published: December 2024

We calculate the intergroup relaxation time νinter −1 of electrons in metals, due to scattering by acoustic phonons in a quantizing magnetic field H. We study the dependence of νinter on temperature, and on the orientation and magnitude of H in two situations: a) For conductors with a low concentration of carriers (semimetals or degenerate semiconductors), b) For typical metals in which the separation between groups is small in comparison with the Fermi momenta. It is shown that the frequency νinter displays quantum oscillations associated with the density of states and also, under certain definite conditions, it is a sharply anisotropic function of the direction of H.
Nuclear quadrupole resonance of 93Nb in the layered compound 2H–NbSe2
Authors: Matukhin V. L. , Shchetkin I. S. , Safin I. A.
Published: December 2024

Nuclear quadrupole interactions and nuclear relaxation in the layered compound 2H–NbSe2 were investigated by using the nuclear quadrupole resonance of 93Nb. The experimental value of the spin–lattice relaxation rate of Nb nuclei was used to estimate the electron density of states at the Fermi level.
Singularities in the magnetoresistance of bismuth thin films in the region of quantum corrections
Authors: Bukhshtab E. I. , Komnik Yu. F. , Butenko A. V. , Andrievskii V. V.
Published: December 2024

The anomalous dependences of the resistance of bismuth thin films (∼ 10‒6 cm) on perpendicular and parallel magnetic fields up to 17 kOe were investigated at 1.5–4.2 °K. The resulting relations were compared with the theory which incorporates quantum corrections to the magnetoresistance related to electron localization and the interference of electron-electron and impurity scattering. The corresponding values of the parameters of the theory are consistent with all the dependences investigated: σ(T), σ(H‖), and σ(H⊥).
Charge trapping by defects arising during cooling of He4 crystals below T
m/2
Authors: Efimov V.B. , Mezhov-Deglin L. P.
Published: December 2024

It is shown that when a radioactive-source diode, frozen into solid helium, is cooled to temperatures two or three times below the melting point Tm of the specimen and is then subsequently warmed up, defects capable of trapping moving charges arise in the hcp crystals of He4. The concentrations of the trapped charges reach values ∼1012 cm−3. Intensive annealing of the defects at temperatures near 0.95 Tm indicates that microdefects, most likely dislocations, serve as trapping centers. Charge trapping on defects is not observed in bcc helium-3 crystals grown in the same apparatus from commercially pure gas (up to 0.2% He4 impurity).
Large-amplitude zero-sound excitations in a Fermi liquid
Authors: Demikhovskii V. Ya. , Maksimova G. Ml.
Published: December 2024

It is shown that, together with ordinary zero sound, strong longitudinal and transverse excitations with velocities smaller than the Fermi velocity can propagate in He3. It is established that the attenuation of such modes is proportional to the small parameter a = (ω0τ)−1≪1 (ω0 is the oscillation frequency of particles captured by the wave, and τ is the relaxation time). The generation of harmonics of a strong zero-sound wave is discussed, and it is shown that the characteristic growth length of the harmonics is of the same order as the attenuation length of the fundamental mode.
Stability of hydrogen impurity atoms in solid H2
Authors: Katunin A. Ya. , Lukashevich I. I. , Orozmamatov S. T. , Sklyarevskii V. V. , Suraev V. V. , Filippov V. V. , Filippov N. I. , Shevtsov V. A.
Published: December 2024

The kinetics of formation of solid mixtures of atomic and molecular hydrogen (concentration 10−4 ≤ NH/NH2 ≤ 10−3) has been studied. It was shown that such a mixture is unstable when the system is heated rapidly and that recombination of hydrogen atoms takes place even at a temperature of 1.5 °K.
Jump-like creep of zirconium at helium temperatures
Authors: Aksenov V. K. , Gindin I. A. , Starodubov Ya. D. , Karaseva E. V.
Published: December 2024

Jump-like creep of polycrystalline zirconium at helium temperatures has been studied over a wide range of applied stresses. It has been shown that unlike the case in other metals studied, the dependence of the strain and the creep rate of zirconium on the applied stress is nonmonotonic. At stresses exceeding those at which jump-like strain begins (more than 25 kg/mm2) the values of ε and ε decrease as σ grows, and creep is absent when σ ≥ 40 kg/mm2. At stresses above 25 kg/mm2 the strain is observed to undergo jumps which can occur with equal probability at any time during the creep process in the specimen. Characteristic features of the structural state of zirconium have been studied at stresses before and after the onset of jump-like strain. On the basis of the data obtained we conclude that the jump-like strain and the interruption of creep in zirconium are due to mass twinning initiated by large dislocation pile-ups against obstacles. The experimental results are analyzed in terms of present-day ideas as to the nature of the instability of plastic flow in materials at low temperatures.
Phonon spectra in ferroelastic KSc(MoO4)2
Authors: Nesterenko N. M. , Fomin V. I. , Kut’ko V. I.
Published: December 2024

We report Raman scattering and IR reflection spectra of KSc(MoO4)2 and other trigonal molybdates and tungstates over the temperature range 4–300 °K. The changes in the spectra in the asymmetric phases are analyzed. The mechanism for the phase transition to the monoclinic phase is discussed.
Thermodynamics of vortex formation in helium II and temperature dependence of critical velocity
Authors: Kiknadze L. V. , Mamaladze Yu. G.
Published: December 2024

A generalized criterion is proposed for the thermodynamic favorability of vortex formation. The criterion is applied to several concrete situations to determine the temperature dependence of the critical velocity.
Electron–phonon interaction in gold and silver microcontacts
Authors: Naidyuk Yu. G. , Yanson I. K. , Lysykh A. A. , Shklyarevskii O. I.
Published: December 2024

Microcontact spectroscopy (MS) has been used to make a detailed investigation of the Au and Ag spectra, and the MC electron-phonon interaction (EPI) function G(eV)=α˜2(eV)F(eV) has been determined where α˜2(eV) is the mean square matrix element of the EPI and F(eV) is the phonon density of states. The MC spectra of Ag show peaks in the region of the transverse (TA) phonons at 10.6±0.1 mV, 12.8±0.1 mV and for longitudinal (LA) phonons at 20.1±0.2 mV;Au shows these respectively at 9.9±0.1 mV (TA) and 17.8±0.1 mV (LA). It has been found that the initial region in the MC spectrum obeys an (eV)2.5 law for small energies 0 ħωmax maxima are observed which correspond to two-phonon processes (TA + LA). A comparison of the MC spectra of Au and Ag with F(eV) shows that α˜2(eV) is not a monotonically decreasing function with increasing energy, but has minima and maxima. The parameter λ for the EPI has also been calculated for these metals.
Dielectric permittivity and molar volume of helium solutions in liquid hydrogen
Authors: Pashkov V. V. , Lobko M. P. , Marinin V. S.
Published: December 2024

The resonance method is used to measure the dielectric permittivity of solutions of helium in liquid hydrogen over the temperature range 17−27.8 °K at pressures to 150 atm. The molar volumes of the liquid phase are determined, and the experimental results are analyzed using perturbation theory for semiquantum liquids.
Microcontact spectroscopy of the electron-phonon interaction in the intermetallide Cu3Au
Authors: Shklyarevskii O. I. , Naidyuk Yu. G. , Yanson I. K.
Published: December 2024

The electron-phonon interaction in ordered and disordered Cu3Au alloys is studied using the method of microcontact spectroscopy. It is shown that the microcontact spectra obtained agree qualitatively with the well-known ω(q) functions for these alloys. The electron-phonon interaction constants are estimated for the intermetallide Cu3Au.
Dynamics of librational motion in N2-type crystals. III. Comparison with experiment
Authors: Antsygina T. N. , Slyusarev V. A. , Freiman Yu. A. , Érenburg A. I.
Published: December 2024

Based on the theory developed by the present authors in preceding papers, the values of the librational frequencies at the Brillouin zone center and the thermodynamic characteristics of solid N2, CO, N2O, and CO2 in the orientationally ordered phase are determined. The results obtained are compared with experimental data.
Changes in the low temperature lattice dynamics of a layered crystal of lead iodide upon intercalation with organic molecules
Authors: Gurevich A. M. , Sukharevskii B. Ya. , Alapina A. V.
Published: December 2024

We report an experimental study of the low temperature specific heat of samples of the layered crystal Pbl2 intercalated with piperidine, pyridine, aniline, and quinoline. Analysis of the results in terms of the model of Syrkin and Feodos’ev provides an estimate of the nature and the degree of variation in the anisotropy of the interatomic interaction as the various intercalants are introduced. An excess specific heat observed in the systems intercalates with aniline and quinoline is attributed to a possible contribution of the surfaces, caused by the finely divided nature of the samples obtained.
Simulation study on the effect of mesoporous layers architecture regulation on carrier transport characteristics of perovskite solar cells
Authors: Liu Yunlong , Yang Chongqiu , Li Hao , Song Rujun , Yang Xiaohui
Published: December 2024

This article proposes to improve the charge carrier transport efficiency in perovskite solar cells (PSCs) by adjusting the pore size of each mesoporous layer, so as to improve the performance of the device. The two-dimensional modeling of PSCs is carried out to clarify the relationship between the pore size of the mesoporous layer and the performance of PSCs. The simulation results show that the control of the pore size of the mesoporous layer can help to form a large potential difference and a deep potential well in the PSC and then improve the carrier transport in the PSC and the carrier collection in the PSC. When the pore size is 20 nm, the effect is the best, and the PSC performance is the best. This study provides theoretical and technical support for the research of mesoporous PSCs and promotes the basic research and commercialization of PSCs, which has important scientific significance and economic value.
Effects of supplementation with 1,25(OH)2D3-glycoside of herbal origin in the diet of nursery piglets
Authors: Gregory Cristine Regina , Bury de Azevedo Liliana , Bickel Amanda Gabriela , Valente Júnior Dante Teixeira , Rodrigues Gustavo de Amorim , Toledo Damares de Castro Fidelis , Carvalho Silvana Teixeira , Nunes Ricardo Vianna , Rennó Luciana Navajas , Artoni Silvana Martinez Baraldi , Sales de Lima Janaína Paolucci , Genova Jansller Luiz , Dalto Danyel Bueno , Carvalho Paulo Levi de Oliveira
Published: December 2024

Context To provide adequate dietary vitamin D in nursery piglets, 1,25(OH)2D3-glycoside could be a potential alternative to supplements currently in use. Aims The effect of this supplement on apparent total tract nutrient digestibility, growth performance, health status, and bone traits was assessed in nursery piglets. Methods Digestibility was assessed in 30 piglets (23.8 ± 3.32 kg), and growth performance in 135 weaned piglets (8.0 ± 0.53 kg). Both trials used randomized complete block designs based on bodyweight, with five treatments: −D3: no vitamin D supplementation; +D3: 100% of the vitamin D requirement supplied as cholecalciferol; and +D3 + 0.5, 1.0, or 1.5 μg of 1,25(OH)2D3-glycoside. Key results From Day 21 to 35, piglets fed D3 + 1.0 diet showed greater average daily gain compared to −D3 or D3 + 1.5, and a greater average daily feed intake was observed in piglets fed +D3, D3 + 0.5, and D3 + 1.0 compared to −D3 or D3 + 1.5. From Day 0 to 7, diarrhoea prevalence was lower in piglets fed D3 + 1.0 compared to −D3, D3 + 0.5, and D3 + 1.5. Across the entire period, animals fed D3 + 1.0 had lower diarrhoea prevalence compared to D3 + 0.5. Serum 25(OH)D3 concentrations was lowest in −D3 piglets. Leukocyte concentrations were greater in piglets on D3 + 1.0 than with D3 + 1.5, whereas eosinophil concentrations were lowest in piglets fed D3 + 0.5. Alkaline phosphatase activity was higher in piglets on +D3 than with D3 + 0.5 or D3 + 1.5. The greatest and lowest bone Ca contents were observed in treatments D3 + 1.5 and D3 + 0.5, respectively. The bone magnesium contents was lowest in piglets fed -D3. Conclusions Adding 1,25(OH)2D3-glycoside to diets containing adequate vitamin D contents as cholecalciferol did not increase serum 25(OH)D3 concentrations, but physiological and metabolic parameters were improved and, in general, 1.0 μg of 1,25(OH)2D3-glycoside showed the best effects on performance, serum vitamin D, health status, and bone traits. Implications This research has provided new information on the effects of 1,25(OH)2D3-glycoside supplementation in diets for nursery piglets and has shown its potential use for bolstering general health.
Exploring the lunar water cycle
Authors: Reiss Philipp
Published: December 2024

The presence of water on the Moon has been indicated by various remote-sensing observations and analyses of returned samples. Several missions are planned to conduct new in situ research on the lunar surface to directly observe and characterize lunar water. A comprehensive characterization of the present forms of water, their abundance, spatial distribution, temporal variation, and possible origin is required to understand the lunar water cycle and the relevance of individual source and sink mechanisms and transformations between the involved volatile species. These processes extend over vastly different scales, and the governing parameters are often insufficiently constrained by experimental and observational data. Here, I present a brief overview of the current state of knowledge on the lunar water cycle, its relevance for lunar science and exploration, and some of the main challenges of modeling and future in situ analyses aiming to substantially advance the understanding of lunar water occurrences.
Oxygen isotope identity of the Earth and Moon with implications for the formation of the Moon and source of volatiles
Authors: Fischer Meike , Peters Stefan T. M. , Herwartz Daniel , Hartogh Paul , Di Rocco Tommaso , Pack Andreas
Published: December 2024

The Moon formed 4.5 Ga ago through a collision between proto-Earth and a planetesimal known as Theia. The compositional similarity of Earth and Moon puts tight limits on the isotopic contrast between Theia and proto-Earth, or it requires intense homogenization of Theia and proto-Earth material during and in the aftermath of the Moon-forming impact, or a combination of both. We conducted precise measurements of oxygen isotope ratios of lunar and terrestrial rocks. The absence of an isotopic difference between the Moon and Earth on the sub-ppm level, as well as the absence of isotope heterogeneity in Earth’s upper mantle and the Moon, is discussed in relation to published Moon formation scenarios and the collisional erosion of Theia’s silicate mantles prior to colliding with proto-Earth. The data provide valuable insights into the origin of volatiles in the Earth and Moon as they suggest that the water on the Earth may not have been delivered by the late veneer. The study also highlights the scientific value of samples returned by space missions, when compared to analyses of meteorite material, which may have interacted with terrestrial water.
Generative AI’s recolonization of EFL classrooms
Authors: Stewart Nicola , Zheng Yangsheng (Danson)
Published: December 2024

Continuation writing was recently introduced as a new element of China’s English as a Foreign Language (EFL)
assessment. The assessment task requires students to complete the story within a set word limit. Preparing students for this task
is challenging for Chinese EFL teachers, as little pedagogical guidance is supplied. Given the recent trend of incorporating
Digital Multimodal Composing (DMC) in Chinese EFL classrooms, using generative AI to provide sample writings presents a potential
option.. This process could be viewed as students creating mentor texts to inform their writing development. We argue that
AI-generated continuation writing samples are predominantly built with complex but culturally hollow sentences. Particularly,
AI-generated samples may prioritize “native-speakerism” in which local cultures are under-represented. Integrating AI-generated
continuation writing samples without cultural awareness risks unintended recolonization of EFL classrooms. We illustrate our
argument with data generated via AI chatbots. We mobilize Hallidayan systemic functional linguistics (SFL) to identify patterns in
complex AI-generated sample texts. This study highlights potential risks when the dominant power reproduced by the language
patterns in AI-generated texts is not critically considered.
Minority language rights at a deadlock
Authors: Climent-Ferrando Vicent
Published: December 2024

This article analyses the European Union’s (EU) approach to the protection of regional or minority languages (RMLs) over the decade 2013 to 2023. It starts by providing a succinct overview of minority language rights in the international arena and focuses its analysis on the European Union, more specifically on the European Commission, the European Parliament and the Council of the EU. The article notes the downward trend in minority language promotion in Europe and highlights the mismatch between the bottom-up, societal demands claiming more support for RMLs and the top-down approach, which shows increasing reluctance to intervene in minority language protection at EU level, on the grounds that languages remain a competence of Member States.
Finite element study on temperature stress of medium strength aluminum alloy wire in high cold area
Authors: E Wenqi , Liu Haodong , Zeng Cong , Wang Dehong , Li Yuebing , Lin Yangkai
Published: December 2024

The extreme climatic conditions in cold regions place higher demands on power transmission, making it urgent to adopt transmission conductors with higher efficiency and minimal environmental impact. This paper conducts a finite element simulation analysis of a new energy-efficient conductor, the JLHA3-275 medium-strength aluminum alloy conductor, under load conditions in the harsh climate of Heilongjiang. A solid finite element model of the medium-strength aluminum alloy conductor was established, and its internal structure was meticulously simulated. The study analyzed the radial temperature distribution and stress distribution of the conductor under cold conditions and yielded the following results: when the temperature ranged from -40°C to -20°C, the overall temperature of the conductor increased by 58°C, and the conductor stress decreased by 40.1 MPa. As the current-carrying capacity increased, the radial temperature difference of the conductor increased from 3.43°C to 10.42°C, and the conductor stress increased with the radial temperature difference. Additionally, the conductor stress decreased as the number of layers increased.
Simulation study of injection rate optimization in hybrid insulator injection molding process based on finite element analysis
Authors: Liu Lin , You Jingfang , Peng Xiangyang , Wang Zheng , Lin Guohai , Zhou Riwen
Published: December 2024

To optimize the injection rate of hybrid insulators during the injection molding process, this paper constructs a common hybrid insulator injection simulation model based on Moldflow software and analyzes the distribution of stresses during the injection molding process of hybrid insulators under three injection rates of 40/50/60 (cm3/s). The results show that the filling effect is uniform at the injection rate of 50 cm3/s and the maximum filling pressure and clamping force peaks are the smallest, which are 54.53 MPa and 601.2 T, respectively.
Comparative analysis of silicone rubber coating process and interface characteristics for porcelain insulators
Authors: Xi Rongjun , Liu Jizhao , Hao Wang , Wang Liuhuo , Lin Junming , Zhang Zhongwen , Huang Zhen , Peng Xiangyang
Published: December 2024

Coating silicone rubber on the surface of porcelain insulators not only retains the stable and reliable mechanical properties of porcelain insulators but also gives them excellent resistance to pollution flashover. However, the interface between the glaze layer and the silicone rubber layer of porcelain insulators may become their electrical weak point. This paper analyzes the difference between the production process of hybrid insulators and factory compounding insulators and carries out interface tests before and after boiling on bar samples. The interface bonding strength of hybrid insulators before and after boiling has no decrease, while the factory composite insulators are easily penetrated by dyes after boiling. Dense small blisters appear at the interface, and the leakage current of the factory compounding insulators is much larger than that of the hybrid insulators after boiling for 100 h. The results of the interface test show that the interface characteristics of the hybrid insulators are better than the factory composite insulators in resisting the aging of water boiling.
Influence of labyrinth clearance on the hydrodynamic performance of a high head Francis turbine
Authors: Kamal M M , Devinar L , Abbas A
Published: December 2024

Francis turbines have a leakage loss from the corresponding labyrinth seals i.e., crown side and a skirt side labyrinth clearance. Therefore, the labyrinth clearance between the runner and turbine cover plays an important role in the hydrodynamic characteristics of the hydro turbine. Generally, the geometrical details of labyrinth clearance are not considered in the numerical model due to complexity involved in modelling and requirement of high computational power that may lead inaccurate prediction of performance of the turbine. In the present investigation, steady-state numerical simulations have been performed on a high head Francis turbine, under different operating conditions, ranging from part load to overload condition, to assess the influence of labyrinth clearance on the hydrodynamic performance of the turbine. FVM method (as discretization method) along with SST k-omega turbulence model has been adopted for computational modelling. The simulation results such as hydraulic efficiency and power output are validated with model test results which was done as per IEC 60193 standard and found satisfactory agreement. Further, the axial thrust force is also computed for different operating conditions and compared with model test results. Based on the simulation results, it has been found that the hydraulic efficiency of turbine with labyrinth clearance was found 0.4% - 1.1% lower than the turbine without labyrinth clearance. The influence of labyrinth clearance on the turbine performance is higher at part-load condition compared to other operating conditions. It is observed that the leakage loss is almost same for all loading conditions at a particular head and fall in the range of 0.61% - 0.81%. Further, the value of axial thrust increases with the increases in discharge value and value of maximum axial thrust was found as 203 kN at overload condition.
On the effect of flow rate on pressure fluctuations and cavitation characteristics in a novel bulb turbine
Authors: Shandilya S , Das S P , Chatterjee D
Published: December 2024

Bulb turbines, having low excavation cost, are promising solutions for harnessing energy from low/ultra-low head run-of-the-river hydropower sources. A novel bulb turbine with no guide vanes, having a uniform efficiency over a range of discharges, is tested. Unsteady numerical simulations are carried out for this bulb turbine over a range of ± 30% of the design flow rate (Q
d) of 0.25 m3/s. Using a normalised Q-criterion to quantify the intensity of swirling flow inside the draft tube, the strong presence of hub and tip vortices is detected. The strength of these vortices increases with an increase in the flow rate. The amplitude and pattern of pressure fluctuations, monitored at different planes along the longitudinal direction, confirm the presence of vortex structures. Frequency analysis of pressure fluctuations shows that the blade passage frequency of the runner is the dominant frequency. With a flow field exhibiting significant fluctuations, a cavitation study is required to characterise the turbine. A turbine operating at various flow rate conditions is susceptible to encountering cavitation, especially at off-design conditions. The current study reports the effect of partial cavitation on the turbine performance at different discharges and assesses the suitability of the novel design from a cavitation perspective.
Design and Development of Guide Vane Cascade Test Rig
Authors: Sahu Rohit , Kumar Sandeep , Gandhi Bhupendra K
Published: December 2024

Flow instabilities around guide vanes of the Francis turbine directly contribute to the pressure pulsation, which is caused by rotor-stator interaction at the inlet of the runner. An experimental guide vane cascade rig is being developed at the Indian Institute of Technology Roorkee, whose flow field is set up to match the actual turbine’s. The test rig is designed for a maximum discharge of 0.06 m3/s in the closed loop, and provisions are made for particle image velocimetry to investigate the flow field around the clear plexi guide vane. Periodic walls of the flow channel between guide vanes are identified as the starting profile for the boundary of the cascade. The cascade will be made of a transparent acrylic sheet with a PIV window size of 230 mm X 59 mm to use a laser system. A 6 mm diameter pressure sensor measures pressure at the suction and non-suction sides of the guide vane. This paper presents the design and arrangements of the test rig components according to the discharge condition. Scale-down design calculations for the turbine are done using IEC 60193. The numerical model of guide vane cascade is prepared using ANSYS CFX. The numerical flow field investigation of the cascade is carried out to find the pressure and velocity distribution at the mid-span location and around the pressure and suction side of the guide vane at best efficiency point. The cascade’s inlet and outlet flow conduits have been optimized through computational fluid dynamics to check the pressure drop across the cascade and match the flow field to the actual turbine. Based on CFD results, the final layout of the test setup will be designed and manufactured.
Experimental and Numerical Investigation of Hydraulic Axial Thrust Fluctuation due to Draft Tube Vortex at partial load on Francis turbine
Authors: Tamura Yuta , Chugun Atsushi , Obuchi Ryomei , Ishihara Tomoaki
Published: December 2024

Operation range extension of Francis turbine is beneficial for effective use of hydraulic energy. However, the swirl flow in the draft tube of Francis turbine becomes large at the operating point far from the design point. As a result, the draft tube vortex occurs and this unsteady behaviour causes various problems such as pressure fluctuation, vibration and noise. Regarding the vibration, the correlation between the draft tube vortex and axial thrust fluctuation was revealed by the model test and CFD analysis in this research.

In the model test, the pressure fluctuations were measured on the upper draft tube and the back chamber of runner crown. The axial thrust fluctuation of runner was measured by thrust meter on the rotational shaft. The unsteady behaviour of the draft tube vortex was captured through photos using high-speed cameras from side of upper draft tube and bottom of the bent draft tube. For the CFD simulation, the assembly of guide vane, runner, draft tube, back chamber of runner crown and the side chamber of runner band were modelled. Both study and unsteady simulation was carried out. From the CFD simulation results the pressure fluctuation at each measuring point and unsteady behaviour of draft tube vortex were obtained and compared with the model test data. Besides, the axial thrust force exerted on runner with respect to time was compared with the thrust fluctuation measured during model test. As the behaviour of draft tube vortex depends on operating point, the pressure fluctuation and thrust fluctuation were also measured from no load to full load condition during the model test. Furthermore, additional unsteady simulations were carried out at the operation point, where the increased thrust fluctuation was observed. As the result, the multiple (3~5 in number) short draft swirls formed with similar circumference as the balance holes at that flow rate. When the low-pressure regions were far from the balance holes, the pressure on the back chamber of the runner was high, and then the axial force on the runner back surface increased. On the other hand, when the low-pressure regions were closer to the balance holes, the pressure on the back chamber decreased, and then thrust on the back surface decreased. This cycle was repeated, causing the hydraulic thrust fluctuation.
Numerical analysis and runner shape optimization of a high head pump-turbine
Authors: Chirkov D , Ustimenko A , Rigin V , Semenova A , Skorospelov V , Turuk P , Seleznev V
Published: December 2024

A set of numerical approaches ranging from the time-consuming unsteady full turbine RANS approach to a very fast periodic steady-stage approach were considered for CFD simulation of flow in Francis pump-turbines. Their computational efforts and accuracy of efficiency prediction were assessed through comparison with experimental data in both pump and turbine modes. It was shown that the unsteady full turbine approach is needed for accurate simulation of low discharge regimes in pump mode. From the other hand, near the optimum and in the high discharge zone, periodic steady-stage approach can be utilized. Next, an approach for multi-objective runner shape optimization of pump-turbine runners was proposed. Thirty free design parameters allowed flexible variation of runner blade shape, hub and band curves, as well as the height of the distributor, linked to the guide vane opening angle. Two or three reference operating points, indicating the turbine performance and head in both turbine and pump modes, were taken for optimization. Cavitation characteristics were accounted for through special constraints. The approach was tested for a 500 m head pump-turbine. It was shown that the optimized runners significantly outperform the initial one in terms of efficiency with comparable cavitation performance.
Analysis of mode-switching of a contra-rotating pump-turbine based on load gradient limiting shutdown and startup sequences
Authors: Fahlbeck J , Nilsson H , Salehi S
Published: December 2024

The contra-rotating pump-turbine (CRPT) is investigated as a runner configuration enabling more efficient low-head pumped hydro storage (PHS). To enhance the flexibility of low-head PHS with a CRPT, it is important to examine mode-switching. This study examines two mode-switching sequences for the CRPT, one turbine-to-pump and one pump-to-turbine. The mode-switching sequences are made as a combination of shutdown and startup sequences of each mode. The goal is to avoid pump and turbine brake modes while maintaining smooth load gradients. The turbine shutdown of the turbine-to-pump mode-switching involves a multi-stage valve closure to reduce the rotational speed of the runners, followed by the pump startup based on a previously optimised sequence. The pump shutdown of the pump-to-turbine mode-switching involves a gradual valve closure and rapid speed down of the runners at the end of the sequence. This is followed by the turbine startup, where a valve opens to generate sufficient flow over the runners before increasing the rotational speed of the runners simultaneously. Both mode-switching sequences require approximately 5 s each, and the largest loads are experienced during the pump mode parts of the sequences. The analysis is carried out using transient computational fluid dynamics with the OpenFOAM open-source software.
An innovative approach to PID governor upgrade for reaching SFC regulation stability
Authors: Dolenc D. , Pekolj J. , Ješe U.
Published: December 2024

Due to the growing number of renewable power sources in electrical grids, there is a need for expanding the number of generating units capable of providing power-frequency ancillary services. Hydropower is emerging as a viable provider of secondary frequency control (SFC) however, many units, esp. those with complex waterway systems, cannot achieve the stability requirements for SFC using conventional PID governors. In the paper, an innovative approach to a PID governor upgrade for a hydropower plant Alpaslan-2 in Turkey is presented. The modelling of the hydraulic system and turbine governor was implemented and tested in the computer software SIMSEN. An upgraded PID governor includes a wicket gate manoeuvring compensation loop, surge tank level oscillation compensation loop, and a feed forward loop. With the improved model, we achieved (in a simulation and on site) a load fluctuation inside the ±1% load range during small and large load reference changes. This allowed the Alpaslan-2 HPP to conform to the Turkish grid SFC and primary frequency control (PFC) requirements.
Large eddy simulation analysis of Francis turbine: A comparison with experimental data and investigation of vortex rope dynamics in the draft tube
Authors: Ramdani Soufiane , Shingai Kenji , Kobayashi Katsutoshi , Sato Koma , Tamura Yuta
Published: December 2024

The rapid deployment of renewable energy is pushing for an increased use of hydro turbines operating at part load conditions. This is done to enable a quick response to shifts in demand and to compensate for fluctuations in supply from other electricity sources. In these conditions, pressure pulsations in the draft tube are generated which affects the structural behaviour of the machine as well as the hydraulic circuit. This research aims to improve the prediction accuracy of pressure pulsations of Francis turbines in the partial load operation using computational fluid dynamics (CFD) simulations. The obtained numerical approach will contribute the decrease of the pressure pulsations in the hydraulic power stations. In this study, the unsteady LES using the FrontFlow/Blue (FFB) solver is adopted and validated. Results for the case with guide vane openings (GVO) set at 50% reveal the presence of a vortex rope in the draft tube, validated by experimental imagery. Fast Fourier transform analysis highlights a frequency corresponding to the vortex rope’s precession speed.