bluuebunny/crossref_metadata_2025_split huggingface dataset:
Length-dependent carbon nanotube film structures and mechanical properties
Authors: Zhang Liwen , Ma Xiaolong , Zhang Yongyi , Bradford Philip D , Zhu Yuntian T 
Published: March 2021

Abstract
We investigated the microstructures of carbon nanotube (CNT) films and the effect of CNT length on their mechanical performance. 230 μm-, 300 μm-, and 360 μm- long CNTs were grown and used to fabricate CNT films by a winding process. Opposite from the length effect on CNT fibers, it has been found that the mechanical properties of the CNT films decrease with increasing CNT length. Without fiber twisting, short CNTs tend to bundle together tightly by themselves in the film structure, resulting in an enhanced packing density; meanwhile, they also provide a high degree of CNT alignment, which prominently contributes to high mechanical properties of the CNT films. When CNTs are long, they tend to be bent and entangled, which significantly reduce their packing density, impairing the film mechanical behaviors severely. It has also been unveiled that the determinant effect of the CNT alignment on the film mechanical properties is more significant than that of the film packing density. These findings provide guidance on the optimal CNT length when attempting to fabricate high-performance macroscopic CNT assemblies.
Temperature-dependent electrical resistivity of macroscopic graphene nanoplatelet strips
Authors: Sibilia S , Bertocchi F , Chiodini S , Cristiano F , Ferrigno L , Giovinco G , Maffucci A 
Published: March 2021

Abstract
This paper studies the temperature dependence of the electrical resistivity of low-cost commercial graphene-based strips, made from a mixture of epoxy and graphene nanoplatelets. An equivalent homogenous resistivity model is derived from the joint use of experimental data and simulation results obtained by means of a full three-dimensional (3D) numerical electrothermal model. Three different types of macroscopic strips (with surface dimensions of cm2) are analyzed, differing in their percentage of graphene nanoplatelets. The experimental results show a linear trend of resistivity in a wide temperature range (−60°C to +60°C), and a negative temperature coefficient . The derived analytical model of temperature-dependent resistivity follows the simple law commonly adopted for conventional conducting materials, such us copper. The model is then validated by using the graphene strips as heating elements by exploiting the Joule effect. These results suggest that such materials can be used as thermistors in sensing or heating applications.
Thermal expansion of water in the science lab—advantages and disadvantages of different experimental setups
Authors: Wagner S , Maut C , Priemer B 
Published: March 2021

Abstract
When the thermal expansion of water is discussed in school or university lessons, functional relationships are often inferred without considering measurement uncertainties. Moreover, in some learning materials, the goal of experimentation and the experimental setup do not match. This creates the wrong picture of scientific practice. In this article we compare five experimental setups with different complexity to investigate the relationship between heat and volume change of water. We take different goals of experimentation into account, as well as measurement uncertainties. We compare the different experimental setups, show advantages and limitations, and give advises for their implementation in the classroom. By doing so, we demonstrate that thermal expansion can be very well adopted for applying scientific practice in school. It is shown that the more complex the experimental setup, the more precise the quantitative significance of the functional relationship.
Shedding synchrotron light on teacher training
Authors: Acioly V , Paiva T , Azevedo G , Rocha T , Picoreti R , Santos A C F 
Published: March 2021

Abstract
This paper aims to introduce the initiative Escola Sirius para Professores do Ensino Médio (ESPEM, Sirius School for High School Teachers) hosted by the Centro Nacional de Pesquisa em Energia e Materiais (CNPEM, Brazilian Center for Research in Energy and Materials) and supported by the Sociedade Brasileira de Física (SBF, Brazilian Physical Society). The program covers the principles and applications of synchrotron radiation with expositive lectures, discussions, and visits to the CNPEM facilities. By using semi structured interviews, a remote focal group and surveys to find out the impact of ESPEM, we observed that the teachers shared their experience and disseminate the acquired knowledge with their peers and students.
Physical characterization of 3He ion beams for radiotherapy and comparison with 4He
Authors: Horst Felix , Schardt Dieter , Iwase Hiroshi , Schuy Christoph , Durante Marco , Weber Uli 
Published: March 2021

Abstract
There is increasing interest in using helium ions for radiotherapy, complementary to protons and carbon ions. A large number of patients were treated with 4He ions in the US heavy ion therapy project and novel 4He ion treatment programs are under preparation, for instance in Germany and Japan. 3He ions have been proposed as an alternative to 4He ions because the acceleration of 3He is technically less difficult than 4He. In particular, beam contaminations have been pointed out as a potential safety issue for 4He ion beams. This motivated a series of experiments with 3He ion beams at Gesellschaft für Schwerionenforschung (GSI), Darmstadt. Measured 3He Bragg curves and fragmentation data in water are presented in this work. Those experimental data are compared with FLUKA Monte Carlo simulations. The physical characteristics of 3He ion beams are compared to those of 4He, for which a large set of data became available in recent years from the preparation work at the Heidelberger Ionenstrahl-Therapiezentrum (HIT). The dose distributions (spread out Bragg peaks, lateral profiles) that can be achieved with 3He ions are found to be competitive to 4He dose distributions. The effect of beam contaminations on 4He depth dose distribution is also addressed. It is concluded that 3He ions can be a viable alternative to 4He, especially for future compact therapy accelerator designs and upgrades of existing ion therapy facilities.
A three-dimensional model of streamer discharges in unsteady airflow
Authors: Niknezhad M , Chanrion O , Köhn C , Holbøll J , Neubert T 
Published: March 2021

Abstract
A 3D fluid model has been developed to simulate streamer discharges in unsteady airflow. The model couples the drift–diffusion equation for charged particles, the Navier–Stokes equations for air, the Poisson’s equation for the electric field, and the Helmholtz equation for photoionization. It allows us to study electrical discharges at different timescales defined by light and heavy particles and to investigate the effects of unsteady airflow. The model treats the time integration in an implicit manner to allow longer time steps, which makes the simulation of long-duration discharges feasible. Moreover, the model uses an unstructured mesh allowing the calculation around solid bodies with complex geometries, and uses adaptive mesh refinement to lower the computation time. The validity and accuracy of the model has been verified by comparing its results with published results, which compares simulations in steady air from six different streamer codes. Our results are consistent and among the most accurate in terms of charge conservation. In order to investigate the influence of wind on streamer discharges, we present results from simulation of a long-duration discharge, in which two successive positive streamers are initiated from a positive polarity electrode in presence of a transverse airflow. This simulation shows that the impact of airflow on positive streamers is driven by the ions, and therefore the airflow effects are seen in ions timescale. Interestingly, we observe that the positive streamer channel, while tilting in the direction of the wind, remains attached to the surface of the electrode. The subsequent positive streamer emerges from the charges remaining from the initial streamer, which have been moved over the electrode surface toward the trailing edge. This mechanism shows and explains the clear tilting of the successive positive streamers in the direction of the wind.
Interference traps waves in an open system: bound states in the continuum
Authors: Sadreev Almas F 
Published: March 2021

Abstract
I review the four mechanisms of bound states in the continuum (BICs) in the application of microwave and acoustic cavities open to directional waveguides. The most simple are symmetry-protected BICs, which are localized inside the cavity because of the orthogonality of the eigenmodes to the propagating modes of waveguides. However, the most general and interesting is the Friedrich–Wintgen mechanism, when the BICs are the result of the fully destructive interference of outgoing resonant modes. The third type of BICs, Fabry–Perot BICs, occurs in a double resonator system when each resonator can serve as an ideal mirror. Finally, the accidental BICs can be realized in the open cavities with no symmetry like the open Sinai billiard in which the eigenmode of the resonator can become orthogonal to the continuum of the waveguide accidentally due to a smooth deformation of the eigenmode. We also review the one-dimensional systems in which the BICs occur owing to the fully destructive interference of two waves separated by spin or polarization or by paths in the Aharonov–Bohm rings. We make broad use of the method of effective non-Hermitian Hamiltonian equivalent to the coupled mode theory, which detects BICs by finding zero-width resonances.
Initial investigations into the MOS interface of freestanding 3C-SiC layers for device applications
Authors: Renz A B , Li F , Vavasour O J , Gammon P M , Dai T , Baker G W C , Via F La , Zielinski M , Zhang L , Grant N E , Murphy J D , Mawby P A , Jennings M , Shah V A 
Published: March 2021

Abstract
This letter reports on initial investigation results on the material quality and device suitability of a homo-epitaxial 3C-SiC growth process. Atomic force microscopy surface investigations revealed root-mean square surface roughness levels of 163.21 nm, which was shown to be caused by pits (35 μm width and 450 nm depth) with a density of 1.09 × 105 cm−2 which had formed during material growth. On wider scan areas, the formation of these were seen to be caused by step bunching, revealing the need for further epitaxial process improvement. X-ray diffraction showed good average crystalline qualities with a full width of half-maximum of 160 arcseconds for the 3C-SiC (002) being lower than for the 3C-on-Si material (210 arcseconds). The analysis of C–V curves then revealed similar interface-trapped charge levels for freestanding 3C-SiC, 3C-SiC on Si and 4H-SiC, with forming gas post-deposition annealed freestanding 3C-SiC devices showing D
IT levels of 3.3 × 1011 cm−2 eV−1 at E
C−E
T = 0.2 eV. The homo-epitaxially grown 3C-SiC material’s suitability for MOS applications could also be confirmed by leakage current measurements.
Wide bandgap tunability of N-alloyed ZnGa2O4 thin films
Authors: Wang Wei-Kai , Liu Kuo-Feng , Wang Sung‐Yu , Guo Jian-Cheng , Huang Shih-Yung 
Published: March 2021

Abstract
ZnGa2O4 films with different nitrogen impurity concentrations were deposited using radio frequency magnetron sputtering in an ammonia (NH3)/Ar gas mixture and were post-annealed at different temperatures, ranging from 600 °C to 900 °C, in NH3 atmosphere. The influence of ammonia partial pressure ratio and nitridation temperature on the microstructure, surface morphology, nitrogen doping profile, and optical properties has been investigated. The optical band gap of ZnGa2O4, under in-situ nitrogen-doping, decreases from 4.6 to 4.1 eV but the primitive ZnGa2O4 crystalline structure does not change. On nitridation, the optical band gap gradually decreases from 4.6 to 2.1 eV and the ZnGa2O4 changes into a zinc gallium oxynitride quaternary alloy structure. Secondary ion mass spectrometry analysis revealed that nitrogen atoms were uniformly distributed in the film. The narrowing, by more than 40%, of the optical band gap is attributed to the hybridization of Zn3d and N2p orbits promote p-d repulsion in the top of the valence band, and the formation of hexagonal wurtzite phase.
Effect of jagged field plate structures on DC and RF performance of AlGaN/GaN HEMTs
Authors: Zou Hao , Yang Lin-an , Ma Xiao-hua , Hao Yue 
Published: March 2021

Abstract
Many field plate structures have been applied to improve the breakdown voltage in high electron mobility transistors (HEMTs). In this paper, the effects of various gate field plate structures on DC and RF performance of AlGaN/GaN HEMTs have been compared. The devices were fabricated on a 3 in sapphire substrate with 0.8 µm gate length, 3 µm source–drain distance, and 50 µm gate width. The results show that the discontinuous field plate structures can improve the cut-off frequency characteristics, but the breakdown characteristics will be weakened. And the increase of the field plate length can improve the breakdown characteristics. Thus, the breakdown characteristics and the cut-off frequency characteristic need to be balanced according to the actual applications by adjusting the length and the area of the field plate structure.
Soft flexible conductive CNT nanocomposites for ECG monitoring
Authors: Chu Marco , Naguib Hani E 
Published: March 2021

Abstract
With the continuing development and interest in wearable electronics and smart textiles, the need for a flexible conductive electrode for use in portable and wearable electrocardiogram (ECG) for long term monitoring rises. Here, we assess the efficacy and performance of various conductive composite polymers in collecting electrical signals from the heart. Thermoplastic polyurethane (TPU), ethylene-vinyl acetate (EVA), and styrene-butadiene-styrene (SBS) were blended with 1%, 2%, 5%, and 10% carbon nanotube (CNT) content using ultrasonication and compression molding techniques. The elastic modulus of the composites increased dramatically at 5% CNT and higher due to the high tensile modulus of the CNTs. The conductivity of each material also increased due to the formation of the conductive network past the percolation threshold. At 10% CNT, SBS, TPU, and EVA had conductivities of 257.9, 51.5, and 2.41 S m−1 respectively. TPU and SBS composites had better strain response due to their linearity between resistance and strain. On the acquisition of electrical signals from the heart, only 5% and 10% SBS-CNT composites were able to detect the ECG waves from the heart. The performance of the material met and even exceeded that of the commercial electrodes with slightly less high frequency noise.
Investigation of AC loss of superconducting field coils in a double-stator superconducting flux modulation generator by using T-A formulation based finite element method
Authors: Liu Yingzhen , Ou Jing , Cheng Yi , Schreiner Fabian , Zhang Yuanzhi , Vargas-Llanos Carlos , Grilli Francesco , Qu Ronghai , Doppelbauer Martin , Noe Mathias 
Published: March 2021

Abstract
In order to reliably make use of superconductors in wind generators, a double-stator superconducting flux modulation generator is proposed here to avoid rotation of field coils and armature windings. The superconducting field coils are located in the inner stator while the armature windings are placed in the outer stator. In this way, the stationary-rotatory couplings of current and cryogenic coolants for superconducting field coils and/or armature windings are removed. Because of the modulation effect of the reluctance rotor between the two stators and the armature reaction field, moving AC magnetic fields are acted on superconducting coils in the inner stator. These moving AC magnetic fields are called magnetic field harmonics in the flux modulation generators. The frequencies of these harmonics are multiples of rotor mechanical frequency. Compared to synchronous superconducting generators, the amplitudes of the harmonics are higher. Even though methods to reduce the amplitudes of harmonics have been studied, the level of the AC loss in the superconducting field coils is still unknown. In this paper, numerical simulations based on the T–A formulation are used to estimate the AC loss of the superconducting field coils in a 10 MW double-stator superconducting flux modulation generator. It is found that by choosing a suitable working temperature, the AC loss of the superconducting field coils without any harmonic reduction methods is not very high, but eddy current loss of copper thermal shield inside the cryostat is significantly higher.
Non-invasive wearable seizure detection using long–short-term memory networks with transfer learning
Authors: Nasseri Mona , Pal Attia Tal , Joseph Boney , Gregg Nicholas M , Nurse Ewan S , Viana Pedro F , Schulze-Bonhage Andreas , Dümpelmann Matthias , Worrell Gregory , Freestone Dean R , Richardson Mark P , Brinkmann Benjamin H 
Published: March 2021

Abstract

Objective. The detection of seizures using wearable devices would improve epilepsy management, but reliable detection of seizures in an ambulatory environment remains challenging, and current studies lack concurrent validation of seizures using electroencephalography (EEG) data. Approach. An adaptively trained long–short-term memory deep neural network was developed and trained using a modest number of seizure data sets from wrist-worn devices. Transfer learning was used to adapt a classifier that was initially trained on intracranial electroencephalography (iEEG) signals to facilitate classification of non-EEG physiological datasets comprising accelerometry, blood volume pulse, skin electrodermal activity, heart rate, and temperature signals. The algorithm’s performance was assessed with and without pre-training on iEEG signals and transfer learning. To assess the performance of the seizure detection classifier using long-term ambulatory data, wearable devices were used for multiple months with an implanted neurostimulator capable of recording iEEG signals, which provided independent electrographic seizure detections that were reviewed by a board-certified epileptologist. Main results. For 19 motor seizures from 10 in-hospital patients, the algorithm yielded a mean area under curve (AUC), a sensitivity, and an false alarm rate per day (FAR/day) of 0.98, 0.93, and 2.3, respectively. Additionally, for eight seizures with probable motor semiology from two ambulatory patients, the classifier achieved a mean AUC of 0.97 and an FAR of 2.45 events/day at a sensitivity of 0.9. For all seizure types in the ambulatory setting, the classifier had a mean AUC of 0.82 with a sensitivity of 0.47 and an FAR of 7.2 events/day. Significance. The performance of the algorithm was evaluated using motor and non-motor seizures during in-hospital and ambulatory use. The classifier was able to detect multiple types of motor and non-motor seizures, but performed significantly better on motor seizures.
Constrained non-crossing Brownian motions, fermions and the Ferrari–Spohn distribution
Authors: Gautié Tristan , Smith Naftali R 
Published: March 2021

Abstract
A conditioned stochastic process can display a very different behavior from the unconditioned process. In particular, a conditioned process can exhibit non-Gaussian fluctuations even if the unconditioned process is Gaussian. In this work, we revisit the Ferrari–Spohn model of a Brownian bridge conditioned to avoid a moving wall, which pushes the system into a large-deviation regime. We extend this model to an arbitrary number N of non-crossing Brownian bridges. We obtain the joint distribution of the distances of the Brownian particles from the wall at an intermediate time in the form of the determinant of an N × N matrix whose entries are given in terms of the Airy function. We show that this distribution coincides with that of the positions of N spinless noninteracting fermions trapped by a linear potential with a hard wall. We then explore the N ≫ 1 behavior of the system. For simplicity we focus on the case where the wall’s position is given by a semicircle as a function of time, but we expect our results to be valid for any concave wall function.
Synthesis and Biological evaluation of Novel Nicotinonitrile derivatives derived from N-Substituted Coumarinyl Chalcones
Authors: Mohammed Mariam M. , Ibraheem Hiba H. , Hussein Amal A. 
Published: March 2021

Abstract
This work included synthesis of several new pyridine derivatives (3a-c) by cyclization of Coumarinyl Chalcones (2a-c) with malononitrile in presence of ammonium acetate. Prepared compounds were diagnosed using Melting point, TLC, FT-IR spectroscopy and 1H-NMR. The synthesized pyridines (3a-c) were screnned for their antibacterial and antifungal activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Klebsiella sp., and Candida albicans. Respectively by diffusion method compounds 3a, 3b and 3c showed good antibacterial activity and by comparison with the medicine Ampicillin. Compounds 3a, 3b and 3c showed moderate antifungal activity compared to the standard drug fluconazole.
Explicit Numerical Model of Solar Cells to Determine Current and Voltage
Authors: Rasheed M. , Mohammed O. Y. , Shihab S. , Al-Adili Aqeel 
Published: March 2021

Abstract
This paper deals with the extraction of the physical parameters of solar cells (a single diode model) from the equivalent circuit of the cell. The extraction is carried out by three different numerical methods with a comparison between them. The first and second methods are a difference of the Newton Raphson algorithm (NRM) and Aitken’s extrapolation algorithm (AEM), respectively. The roots of the nonlinear equation of this cell have been described and solved using the three methods. The proposed method is tested to solve the output voltage; current and power of this cell from the roots of this equation with the various values of load resistance RL.
Investigation of structural, morphology, optical properties and electrical transport conduction of Li0.25Na0.75CdVO4 compound
Authors: Enneffatia M. , Rasheed M. , Louatia B. , Guidaraa K. , Shihab S. , Barillé R. 
Published: March 2021

Abstract
Polycrystalline Li0.25Na0.75CdVO4 was synthesized via a solid-state technique under air atmosphere. It is found that X-ray diffraction peaks are listed as orthorhombic Na2CrO4 structure belonging to the space group Cmcm. Composition of elements was examined by energy dispersive X-ray analysis (EDX or EDS). Grains size and morphology of the present material were investigated by scanning electron microscopy (MEB) and atomic force microscopy (AFM). Electrical measurements were performed using complex impedance spectroscopy. Impedance curves confirm the presence of two contributions and an equivalent circuit was suggested. An electrical transport in the material as a thermally activated process has been achieved using DC conductivity. While; AC conductivity is analyzed by the non-overlapping small polar on tunneling (NSPT) conduction mechanism. Refractive index, extinction coefficient, and band gap energy were determined from ellipsometric measurements.