bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of ferrofluid magnetization on transformer temperature rise
Authors: Rajňák Michal , Franko Marek , Paulovičová Katarína , Karpets Maksym , Parekh Kinnari , Upadhyay Ramesh , Kurimský Juraj , Dolník Bystrík , Cimbala Roman , Havran Peter , Timko Milan , Kopčanský Peter 
Published: May 2022

Abstract
In electrical engineering, the heat transfer can be enhanced by changing the thermophysical properties of insulating oils. In this paper, a single-phase power transformer with a nominal power of 5 kVA is subjected to a temperature rise test with three different transformer liquids. The first test is carried out with a novel gas-to-liquid transformer oil applied as a cooling and insulating medium. The other tests are conducted with ferrofluids based on this oil and MnZn ferrite nanoparticles of a low and a high nanoparticle concentration. The ferrofluids are characterized by magnetization curves, magnetic susceptibility and temperature-dependent magnetization measurements. The nanoparticle size distribution is determined from dynamic light scattering and the magnetization data. From the temperature rise profiles of the transformer at various inner locations, it has been found that the low-concentrated ferrofluid significantly reduces the transformer temperature rise. The enhanced cooling performance is ascribed to the thermomagnetic and natural convection, and increased thermal conductivity. The application of the ferrofluid with the high nanoparticle concentration resulted in a remarkable increase of the transformer temperature rise. The deteriorative cooling effect is attributed to the hindered natural and thermomagnetic convection due to the high ferrofluid magnetization and strong magnetic interaction of the ferrofluid with the magnetic field near the transformer core.
Short-time dynamics in active systems: the Vicsek model
Authors: Rubio Puzzo M Leticia , Loscar Ernesto S , De Virgiliis Andrés , Grigera Tomás S 
Published: May 2022

Abstract
We study the short-time dynamics (STD) of the Vicsek model (VM) with vector noise. The study of STD has proved to be very useful in the determination of the critical point, critical exponents and spinodal points in equilibrium phase transitions. Here we aim is to test its applicability in active systems. We find that, despite the essential non-equilibrium characteristics of the VM (absence of detailed balance, activity), the STD presents qualitatively the same phenomenology as in equilibrium systems. From the STD one can distinguish whether the transition is continuous or discontinuous (which we have checked also computing the Binder cumulant). When the transition is continuous, one can determine the critical point and the critical exponents.
Edge magnetization and thermally induced spin current in nanostructured graphene
Authors: Phung Thu Thi , Nguyen Mai Thi , Pham Lien Thi , Ngo Lan Thi , Nguyen Tung Thanh 
Published: May 2022

Abstract
In this work, the magnetic states and thermally induced spin currents in graphene nanoflake sizes with different sizes and shapes have been investigated using Hubbard model combined with non-equilibrium Green’s function method. In addition to the antiferromagnetic (AFM) state governed by the sizes, shapes, armchair bond densities, and Coulomb energy, our calculations have also pointed out the emergence of ferromagnetic (FM) and complex magnetic states when the gate voltage is invoked in the graphene nanoflakes. More prominently, by exploiting the geometric symmetry of the nanoflakes without external fields, a pure spin current and zero charge current are generated in spin caloritronic device when the graphene nanoflakes are both in the AFM and FM states. The formation of pure spin currents driven by temperature difference depends on the graphene nanoflakes’ size, shape, temperature and gate voltage as well. The study also shows the outstanding advantages of diamond-shaped graphene nanoflakes in both magnetic properties and spin currents. This result paves the way for the possibility of practical applications of graphene materials in spintronics and spin caloritronics.
Evidence of phase stability, topological phonon and temperature-induced topological phase transition in rocksalt SnS and SnSe
Authors: Sihi Antik , Pandey Sudhir K 
Published: May 2022

Abstract
Both SnS and SnSe have been experimentally and theoretically confirmed as topological crystalline insulators in native rocksalt structure. Here, phononic structure, thermodynamic properties and temperature dependent electron–phonon interaction (EPI) have investigated for both the materials in rocksalt phase. Previously performed theoretical studies have predicted the phase instability of SnS in this crystal structure at ambient condition. But, after a detailed study performing on the phonon calculation of SnS, we have predicted the phase stability of SnS with considering the Sn 4p orbitals as valence states in ab-initio calculation. The importance of long range Coulomb forces along with the themodynamical properties are also described in detailed for both materials. The computed value of Debye temperature (

Θ

D

) for SnS (SnSe) is ∼315.0 K (∼201.7 K). The preliminary evidence of topological phonon is found along X–W direction, where the linear band touching is observed as compared to type II Weyl phononic material ZnSe (Liu et al 2021 Phys. Rev. B 103 094306). The topological phase transition is seen for these materials due to EPI, where non-linear temperature dependent bandgap is estimated. The predicted value of transition temperature for SnS (SnSe) is found to be ∼700 K, where after this temperature the non-trivial to trivial topological phase is seen. The strength of EPI shows more stronger impact on the electronic structure of SnS than SnSe material. The reason of non-linear behaviour of bandgap with rise in temperature is discussed with the help of temperature dependent linewidths and lineshifts of conduction band and valence band due to EPI. The present study reveals the phase stability of SnS along with the comparative study of thermal effect on EPI of SnS and SnSe. Further, the possibility of temperature induced topological phase transition provides one of important behaviour to apply these two materials for device making application.
A laser-induced breakdown spectroscopy method to assess the stochasticity of plasma-flame transition in sprays
Authors: de Oliveira Pedro M , Sitte Michael Philip , Kotzagianni Maria , M Allison Patton , Mastorakos Epaminondas 
Published: May 2022

Abstract
An experimental approach is presented to evaluate the impact of plasma composition arising from pulse-to-pulse energy and mixture fluctuations on the non-resonant laser-induced ignition of sprays. This allows for spark events to be conditioned on the successful or failed establishment of a flame kernel, a phase dominated by plasma decomposition and recombination reactions and the on-set of combustion reactions, that is, independent of the subsequent flame growth phase controlled by propagation phenomena only, such as fuel availability and turbulent strain. For that, laser-induced breakdown spectroscopy of the spark-generated plasma is carried out, followed by OH

∗

high-speed imaging of the kernel. Exploratory experiments in spatially uniform and polydisperse kerosene droplet distributions in a jet suggest that the hydrogen concentration in the plasma deriving from the fuel dissociated by the spark is closely related to the generated OH

∗

radicals levels and, in turn, with the success of establishing a flame kernel. This suggests that the ignition process is heavily controlled by mixture fluctuations at the spark, inherent of spray flows. The instantaneous mixture at the spark is estimated with a stochastic model, with the probability density function of the equivalence ratio exhibiting values higher than twice the mean value, while the highest probability occurs at lean conditions between the gaseous equivalence ratio and the overall equivalence ratio. The findings corroborate insights on the early-phase ignition obtained from direct numerical simulations, and the framework paves the way for the development of smart online engine-health tools to assess relight capability in future aeroengines.
Fragmented graphene synthesized on a dielectric substrate for THz applications
Authors: Rehman Hamza , Golubewa Lena , Basharin Alexey , Urbanovic Andzej , Lahderanta Erkki , Soboleva Ekaterina , Matulaitiene Ieva , Jankunec Marija , Svirko Yuri , Kuzhir Polina 
Published: May 2022

Abstract
Fragmented multi-layered graphene films were directly synthesized via chemical vapor deposition (CVD) on dielectric substrates with a pre-deposited copper catalyst. We demonstrate that the thickness of the sacrificial copper film, process temperature, and growth time essentially influence the integrity, quality, and disorder of the synthesized graphene. Atomic force microscopy and Kelvin probe force microscopy measurements revealed the presence of nano-agglomerates and charge puddles. The potential gradients measured over the sample surface confirmed that the deposited graphene film possessed a multilayered structure, which was modelled as an ensemble of randomly oriented conductive prolate ellipsoids. THz time domain spectroscopy measurements gave the ac conductivity of the graphene flakes and homogenized graphitic films as being around 1200 S cm−1 and 1000 S cm−1, respectively. Our approach offers a scalable fabrication of graphene structures composed of graphene flakes, which have effective conductivity sufficient for a wide variety of THz applications.
Improving coronary ultrafast Doppler angiography using fractional moving blood volume and motion-adaptive ensemble length
Authors: Zhang N , Nguyen M B , Mertens L , Barron D J , Villemain O , Baranger J 
Published: May 2022

Abstract
Coronary microperfusion assessment is a key parameter for understanding cardiac function. Currently, coronary ultrafast Doppler angiography is the only non-invasive clinical imaging technique able to assess coronary microcirculation quantitatively in humans. In this study, we propose to use fractional moving blood volume (FMBV), proportional to the red blood cell concentration, as a metric for perfusion. FMBV compares the power Doppler in a region of interest (ROI) inside the myocardium to the power Doppler of a reference area in the heart chamber, fully filled with blood. This normalization gives then relative values of the ROI blood filling. However, due to the impact of ultrasound attenuation and elevation focus on power Doppler values, the reference area and the ROI need to be at the same depth to allow this normalization. This condition is rarely satisfied in vivo due to the cardiac anatomy. Hereby, we propose to locally compensate the attenuation between the ROI and the reference, by measuring the attenuation law on a phantom. We quantified the efficiency of this approach by comparing FMBV with and without compensation on a flow phantom. Compensated FMBV was able to estimate the ground-truth FMBV with less than 5% variation. This method was then adapted to the in vivo case of myocardial perfusion imaging during heart surgery on human neonates. The translation from in vitro to in vivo required an additional clutter filtering step to ensure that blood signals could be correctly identified in the fast-moving myocardium. We applied the singular value decomposition filter on temporal sliding windows whose lengths were a function of myocardium motion. This motion-adaptive temporal sliding window approach was able to improve blood and tissue separation in terms of contrast-to-noise ratio, as compared to well-established constant-length sliding window approaches. Therefore, compensated FMBV and singular value decomposition assisted with motion-adaptive temporal sliding windows improves the quantification of blood volume in coronary ultrafast Doppler angiography.
Linear and nonlinear excitation of TAE modes by external electromagnetic perturbations using ORB5
Authors: Sadr Mohsen , Mishchenko Alexey , Hayward-Schneider Thomas , Koenies Axel , Bottino Alberto , Biancalani Alessandro , Donnel Peter , Lanti Emmanuel , Villard Laurent 
Published: May 2022

Abstract
The excitation of toroidicity-induced Alfvén eigenmodes (TAEs) using prescribed external electromagnetic perturbations (hereafter ‘antenna’) acting on a confined toroidal plasma, as well as its nonlinear couplings to other modes in the system, is studied. The antenna is described by an electrostatic potential resembling the target TAE mode structure along with its corresponding parallel electromagnetic potential computed from Ohm’s law. Numerically stable long-time linear simulations are achieved by integrating the antenna within the framework of a mixed representation and pullback scheme (Mishchenko et al 2019 Comput. Phys. Commun.
238 194). By decomposing the plasma electromagnetic potential into symplectic and Hamiltonian parts and using Ohm’s law, the destabilizing contribution of the potential gradient parallel to the magnetic field is cancelled in the equations of motion. Besides evaluating the frequencies and the growth/damping rates of excited modes compared to referenced TAEs, we study the interaction of antenna-driven modes with fast particles and indicate their margins of instability. Furthermore, we show the first nonlinear simulations in the presence of a TAE-like antenna exciting other TAE modes, as well as global Alfvén eigenmodes with different toroidal wave numbers from that of the antenna.
Relativistic high-order harmonic generation by a femto-second radially polarized laser pulse irradiating a ring plasma grating
Authors: Zhang S J , Zhuo H B , Yin Y , Zou D B , Zhao N , Zhou W M 
Published: May 2022

Abstract
A novel scheme for generating relativistic high-order harmonics by a relativistic radially polarized laser interacting with a plasma annular grating is proposed. The particle-in-cell results show that the radial laser field can drive the relativistic electron bunches to oscillate radially in all azimuth directions, resulting in the emission of strong harmonics. Firstly, the interference of the laser field on the plasma grating structure significantly enhances the radiated harmonics which match the phase conditions. Secondly, due to the common ring symmetry of the grating structure and laser polarization, the transverse distribution of harmonics presents a Bessel form, and there is a sharp bright spot in the center with relativistic intensity. Such high-intensity short-wave structured harmonics have broad applications in areas such as plasma diagnostics, high resolution imaging and detection.
Laser-generated supersonic plasma jets and shocks in a transverse magnetic field
Authors: Bohlin H , Brack F-E , Cervenak M , Chodukowski T , Cikhardt J , Dostál J , Dudžák R , Hubner J , Huo W , Jelinek S , Klír D , Kroll F , Krupka M , Krůs M , Pisarczyk T , Rusiniak Z , Schramm U , Nguyen-Bui T-H , Weber S , Zaraś-Szydłowska A , Zeil K , Kumar D , Schlegel T , Tikhonchuk V 
Published: May 2022

Abstract
The influence of a transverse magnetic field on the formation and evolution of supersonic plasma jets and shocks was studied experimentally, and compared with 3D numerical simulations. An improved jet collimation was seen due to the change in the magnetic field topology restricting the radial expansion of the ablated plasma. The magnetic field was also shown to strongly affect the shock structures, both indirectly through the modified jet geometry, as well as due to a compression of the field lines in the shock region. The interaction characteristics were found to depend on the relative contribution of the magnetic and plasma pressure in balancing the ram pressure of the jet.
Experimental investigations of plasma dynamics in the hysteresis regime of reactive RF sputter processes
Authors: Roggendorf J , Berger B , Eremin D , Oberberg M , Engel D , Wölfel C , Zhang Quan-Zhi , Awakowicz P , Lunze J , Schulze J 
Published: May 2022

Abstract
Reactive radio frequency (RF) sputter processes are highly relevant for thin film deposition, but there is no complete understanding of the fundamentals of their operation. While the Berg model describes the hysteresis regime considering the oxygen coverage of the boundary surfaces, a complete fundamental understanding of the plasma–surface interactions and their effects on the discharge is still missing. In this work, we provide such fundamental insights based on an extensive experimental analysis of the physics in the hysteresis regime of magnetized reactive sputter processes, where the same reactive gas admixture can lead to different discharge characteristics depending on the previous state of the plasma. A variety of plasma and surface diagnostics is used to reveal these insights. A low pressure capacitively coupled RF discharge (CCP, 13.56 MHz) with a magnetron-like magnetic field topology adjacent to the target is operated in argon gas with a variable admixture of O2. The applied RF power, the gas flows/pumping speed, as well as the neutral gas pressure are changed systematically to understand the effects of these external control parameters on the hysteresis regime. The magnetic asymmetry effect is found to play an important role, since an axially non-uniform magnetic field is used to realize a local electron confinement at the target. Similar to process control in applications, the DC self-bias is measured to stabilize the surface composition using a feedback controller with the oxygen gas flow as the manipulated variable.
Electron impact studies on the imidogen (NH+) molecular ion
Authors: Ghosh R , Chakrabarti K , Choudhury B S 
Published: May 2022

Abstract
Low energy electron collision calculations have been performed on the imidogen molecular ion NH+ at its equilibrium geometry using the R-matrix method. A suitable model is first built to represent the NH+ target ion. With this target model we have performed scattering calculations to obtain cross sections for electronic excitation from the X2Π ground state of NH+ to few of its excited states. The excitation cross sections are then used to approximately obtain the cross section for dissociation for the production of N+ ions. We also report the cross sections for rotational excitation of NH+ in its ground state within the Coulomb–Born approximation.
A flexure hinged piezoelectric stick–slip actuator with high velocity and linearity for long-stroke nano-positioning
Authors: Qiao Guangda , Ning Peng , Gao Qi , Yu Yang , Lu Xiaohui , Yang Shitong , Cheng Tinghai 
Published: May 2022

Abstract
It is difficult to simultaneously achieve high linearity, high velocity, and high resolution for long-stroke piezoelectric actuators due to their discontinuity. To improve the velocity and linearity, a linear piezoelectric stick–slip actuator is proposed inspired by the fast response characteristics of piezoelectrics, which can achieve dynamic adjustment of the normal pressure by the design of flexure hinge structure. Additionally, a new dynamic model of piezoelectric stick–slip is proposed, and the step characteristics of the backward motion to displacement surge are simulated by the proposed model. The dynamic adjustment of the normal pressure can be increased by adding the inertia block to the end of the driving arm. Compared with the performance of the actuator without an inertia block, the velocity is increased, the backward motion is suppressed, and the linearity is improved. Moreover, the linear fitting correlation coefficients R
2 of displacement curve is used to evaluate the linearity of the actuator, which can reach 0.9999 at both low (10 Hz) and high (1300 Hz) frequencies, the maximum velocity is 101.76 mm s−1, the stroke is 75 mm, and the resolution is 25 nm.
Tunable laser spectroscopy for carbon dioxide capnography and water vapor sensing inside a breathing mask: application to pilot life support
Authors: Christensen Lance E , Mansour Kamjou , Pleil Joachim D , Troy Robert F 
Published: May 2022

Abstract
Tunable laser spectroscopy (TLS) near 2683 nm was used to measure carbon dioxide and water vapor inside a pilot mask during jet fighter flights. Measurement frequency was 100 Hz in order to capture breathing profiles and other gas flow dynamics. Analysis of the full inhalation and exhalation breathing cycle allowed precise monitoring of breathing performance and interaction of the pilot with the life-support system. Measurements revealed dynamic phenomena pertaining to mechanical gas flow and pilot respiration that may be used to understand gas delivery stresses imposed upon the pilot and pilot physiology during flight. Typically, such measurements are made with non-dispersive infrared instrumentation for only carbon dioxide with intrinsic challenges regarding time and optical resolution. The TLS approach is a major advance because the sensor is placed directly into the mask improving its time response and enabling use of water vapor measurements that are less impacted from memory effects. This article presents the implementation of TLS and shows highly time-resolved pilot breathing data for high-performance aircraft tests.
A comparative environmental study of aqueous extracts of ginger and grapes to protect hepatocytes in Albino rabbits and a comparison of extracts in preserving Awassi lamb meat from oxidation
Authors: khaleel Zinah Ibrahim , Abdulqader Abeer T. , Al-Sammarie Aseel Muthana Yousif , Mustafa Mohammed Ahmed 
Published: May 2022

Abstract
The present study was conducted on white rabbits of Swiss origin demonstrate the effect of hydrogen peroxide on showing tissue (damage to body parts) of organs, and treatment with water-based ginger extract and water-based grape extract.
Histological signs appeared in hydrogen peroxide of liver tissues the occurrence of tissue changes in hepatic cell represented by of some cases of infiltration in lymphocytes, necrosis of the cytoplasm of cells, and degeneration of the nucleus. The results of the histological examination showed the group treated with aqueous ginger extract and a group of the aqueous grape extract showed the natural shape closest to the histological sections of the control group.
The study included a statement of the effect of adding an aqueous extract of ginger and grape seed extract on thigh meat taken from a calf immediately after slaughter.
That the meat of the Awassi lambs had the highest percentage of influence on the chemical characteristic (fat) at the degree of freezing (-18 m) of the cotton thigh piece in a group that would extract grapes and that the meat of the Awassi lambs showed that there was no significant difference in the chemical characteristic (ash) at the degree of freezing (-18m) for the thigh piece at (p≤ 0.05) compared with the control treatment and the treatments of grape extract and ginger.
The highest fat percentage was in the group of grape extract, while the ash percentage was not significant, in the thigh meat.
And that this study has demonstrated stability in the composition of meat, which was reflected in the improvement of meat’s ability to bind water, and it showed efficiency as an antioxidant in hindering fat oxidation and protecting meat pigment from oxidation after 90 days of frozen storage.