bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of sp–d exchange constants revisited
Authors: Andriotis Antonis N , Menon Madhu 
Published: January 2021

Abstract
We present a new computational method for estimating the sp–d exchange constant,

J

eff

s
p
−
d

, applicable to transition metal doped diluted magnetic semiconductors, transition metal oxides, and 2D- and 3D- dichalcogenides. The proposed method is based on results describing the variation of the magnetic features of a doped system with the variation of its magnetization density (M). The results for

J

eff

s
p
−
d

(

M

)

obtained with the proposed method are compared with the corresponding results,

J

eff

s
p
−
d

(

Δ

E

VBM

)

, obtained from estimations of the spin electron orbital splitting, ΔE
VBM, at the valence band maximum (VBM). The latter is estimated in two ways; either directly from plots of the band structure calculations or by calculating the energy difference between the band-centers of the spin-up and spin-down electron density of states of the doped systems. Despite the inherent drawbacks in these two estimation methods for ΔE
VBM, they lead to equivalent results and the corresponding

J

eff

s
p
−
d

(

Δ

E

VBM

)

are in good agreement with the

J

eff

s
p
−
d

(

M

)

ones. Ab initio results obtained for the 2D-MoS2 doped with 3d-series transition metals are presented to demonstrate the validity and applicability of the proposed computational schemes for obtaining

J

eff

s
p
−
d

. The proposed methods can be utilized as useful tools in the search of new materials for spintronics and valleytronics applications.
Atomic structure, tensile property, and dislocation behavior of Fe–W interfaces from molecular dynamics simulation
Authors: Mi S T , Wu C Y , Liu L C , Fan J L , Gong H R 
Published: January 2021

Abstract
Molecular dynamic simulations based on a recently constructed potential reveal that quasi-repeating patterns could appear in both Fe(110)/W(110) and W(110)/Fe(110) interfaces, and that three kinds of atomic displacements of Fe atoms because of the Fe–W interaction intrinsically bring about the interesting quasi-repeating patterns of the Fe–W interfaces. It is also found that the Fe–W interface becomes more brittle with less critical strains under tensile loading than pure Fe or W, which is fundamentally attributed to the movement of the interface dislocations as a result of the lattice mismatch between Fe and W. Interestingly, the dislocation loops could be formed in the Fe–W interface under tensile loading due to the pinning of the

100

edge dislocations by the edge dislocations of

1
/
2

111

, whereas no dislocation loop would be generated in pure Fe or W.
Hysteresis in centrosymmetric CuPbI3 perovskite halide: apolar dielectric or orientable dielectric?
Authors: Bharti Prem C , Jha Pardeep K , Jha Priyanka A , Singh Prabhakar 
Published: January 2021

Abstract
We demonstrated the change in polarization behaviour at the surface/interface before and after light through Havriliak–Negami equation of lesser known CuPbI3. We have synthesized CuPbI3 through cold sintering technique and the polarization mechanisms are altered by increasing (cold) sintering temperature. The structure of CuPbI3 was not known and we predicted it to be hexagonal (R

3

̄

m) with 21R prototype representation. The hysteresis is reported to be affected by ferroelectricity (reorientable dipoles with non-centrosymmetry), to inspect this a centrosymmetric CuPbI3 is taken. In spite of centrosymmetry, we observed that the hysteresis area and shape of IV curve in AM 1.5 G sunlight shows the drastic variation with the change in polarization behaviour. Our experimental results suggest that apolar dielectric behaviour is the cause of I–V hysteresis rather than robust ferroelectric polarization (which was absent in the present case).
Surface temperature condition monitoring methods for aerospace turbomachinery: exploring the use of ultrasonic guided waves
Authors: Yule Lawrence , Zaghari Bahareh , Harris Nicholas , Hill Martyn 
Published: January 2021

Abstract
Turbine blades and nozzle guide vanes (NGVs) are operated at extreme temperatures in order to maximise thermal efficiency and power output of an engine. In this paper the suitability of existing temperature monitoring systems for turbine blades and nozzle guide vanes are reviewed. Both offline and online methods are presented and their advantages and disadvantages are examined. The use of offline systems is well established but their online equivalents are difficult to implement because of the limited access to components. There is the need for an improved sensor that is capable of measuring temperature in real time with minimum interference to the operating conditions of the engine, allowing operating temperatures to be increased to the limits of the components and maximising efficiency. Acoustic monitoring techniques are already used for a large number of structural health monitoring applications and have the potential to be adapted for use in temperature monitoring for turbine blades and NGVs. High temperatures severely affect the response of ultrasonic transducers. However, waveguides and buffer rods can be used to distance transducers from extreme conditions, while piezoelectric materials such as Yttrium Calcium Oxyborate single crystals and Aluminum Nitride have been developed for use at high temperatures. A new monitoring approach based on ultrasonic guided waves is introduced in this paper. The geometry of turbine blades and NGVs allows Lamb waves to propagate through their structure, and the presence of numerous cooling holes will produce acoustic reflections that can be utilised for monitoring temperature at a number of locations. The dispersive nature of Lamb waves makes their analysis difficult; however, wave velocity in dispersive regions is particularly sensitive to changes in temperature and could be utilised for monitoring purposes. The proposed method has the potential to provide high resolution and accuracy, fast response times, and the ability to place sensors outside of the gas path. Further research is required to develop a monitoring system based on the use of guided waves in extreme environments.
Bearing fault diagnosis method based on similarity measure and ensemble learning
Authors: Wang Zhijian , Wang Chen , Li Naipeng 
Published: January 2021

Abstract
Ensemble learning aggregates the predictions of diverse predictors. Most existing ensemble learning methods gather the base classifiers based on the weight of accuracy. However, if the weight is adjusted only according to the correct rate of the base classifiers, it ignores the different types of errors caused by different working principles of the base classifiers. Blindly taking the correct rate of the basis classifier as the weight will increase the probability of the classifier making the same mistake and thus reduce the correct rate. To address this problem, this paper proposes a multi-round voting method based on similarity measurement. In the proposed method, the characteristic parameters of the data are extracted and PCA dimensionality reduction is used to train several base classifiers, which achieved high accuracy of about 90% at first. Then, we extract the confusion matrix of these base classifiers to facilitate the calculation of the similarity measurement matrix and the obtainment of the similarity matrix between base classifiers. Later, on the basis of the number of base classifiers and the values of the similarity matrix, we set a certain number of similar thresholds. Finally, according to the comparison of similarity value and similarity thresholds, a multi-round voting classifier is trained. By comparing the hard voting classifier, multi-round voting classifier and their base classifiers, the experimental results verify that the multi-round voting classifier has higher accuracy than other methods.
Multiferroic ground states in free standing perovskite-based nanodots: a density functional theory study
Authors: Vishnu Karthik Guda , Reeve Samuel Temple , Strachan Alejandro 
Published: January 2021

Abstract
We use density functional theory to investigate the possibility of polar and multiferroic states in free-standing, perovskite-based nanodots at the atomic limit of miniaturization: single unit cells with terminations which allow centro-symmetry. We consider both A-O and B-O2 terminations for three families of nanodots: (i) A = Ba with B = Ti, Zr, and Hf; (ii) A = Ca and Sr with B = Ti; and (iii) A = Na and K with B = Nb. We find all A–O terminated dots to be non-polar and to exhibit cubic symmetry (except for K8NbO6), regardless of the presence of ferroelectricity in the bulk. In contrast, all the B–O2 terminated nanodots considered relax to a non-cubic ground state. Rather surprisingly, all of these structures exhibit polar ground states (except NaNb8O12). We propose a new structural parameter, the cluster tolerance factor (CTF), to determine whether a particular chemistry will result in a polar ground state nanodot, analogous to the Goldschmidt factor for bulk ferroelectrics. In addition, we find that all A–O terminated (except Ca8TiO6) and all polar B–O2 terminated nanodots are magnetic, where none show magnetism in the bulk. As with bulk systems, multiferroicity in the B–O2 terminated dots originates from separation between spin density in peripheral B atoms and polarity primarily caused by the off-center central A atom. Our findings stress that surface termination plays a crucial role in determining whether ferroelectricity is completely suppressed in perovskite-based materials at their limit of miniaturization.
Anisotropic heat transfer properties of two-dimensional materials
Authors: Yang Jiawei , Liu Changqing , Xie Huaqing , Yu Wei 
Published: January 2021

Abstract
The anisotropic heat transfer properties of two-dimensional materials play an important role in controlled heat transfer and intelligent heat management. At present, there are many references on anisotropic heat transfer of two-dimensional materials, but less systematic review of their development status, problems, and future directions. In this paper, intrinsic anisotropic heat transfer of two-dimensional materials, influencing factors and control means are introduced. The preparation methods of thin film with two-dimensional material and the influence factors of macroscopic anisotropic thermal properties are summarized. The technology of two-dimensional material oriented arrangement in matrix and the influence factors of macroscopic anisotropic thermal properties of the composite are outlined.
A robust magnesiothermic reduction combined self-activation strategy towards highly-curved carbon nanosheets for advanced zinc-ion hybrid supercapacitors applications
Authors: Wang Dewei , Chen Guoxian , Pan Zhongmou 
Published: January 2021

Abstract
Aqueous zinc-ion hybrid supercapacitors are considered to be a newly emerging electrochemical energy storage devices. However, the exploration and design of advanced cathode materials remain a huge challenge. Herein, we developed a versatile one-step magnesiothermic reduction and self-activation process for the synthesis of highly-curved carbon nanosheets (HCCNs) with hierarchical pore structures. In this process, low-molecular weight organic potassium salts (e.g. potassium bitartrate, potassium acetate, potassium oxalate, potassium formate, potassium oleate, potassium sorbate), which usually used as the chemical activating reagents, serve as the carbon source whereas the Mg power acts as the reducing agent. The resulting HCCNs possess hierarchical porosity and unique HCCN geometry which can afford abundant active sites for charge accumulation as well as the highly efficient ions diffusion kinetics. Because of the high ratio of surface-controlled capacitive contribution and high ions diffusion coefficient, the optimized sample can exhibit excellent charge storage performance with an impressive reversible capacity (200.2 mAh g–1), excellent rate capability, and good cyclic stability. The excellent capacitive behaviors combined with the feasible synthetic procedure make the present synthetic protocol a promising choice towards well-designed nanocarbons for electrochemical energy storage applications.
Electronic excitation in graphene under single-particle irradiation
Authors: He Wanzhen , Chen Changqing , Xu Zhiping 
Published: January 2021

Abstract
Single-particle irradiation is a typical condition in space applications, which could be detrimental for electronic devices through processes such as single-event upset or latch-up. For functional devices made of few-atom-thick monolayers that are entirely exposed to the environment, the irradiation effects could be manifested through localized or delocalized electronic excitation, in addition to lattice defect creation. In this work, we explore the single-H irradiation effects on bare or coated graphene monolayers. Real-time time-dependent density functional theory-based first-principles calculation results elucidate the evolution of charge densities in the composite system, showing notable charge excitation but negligible charge deposition. A hexagonal boron nitride coating layer does not protect graphene from these processes. Principal component analysis demonstrates the dominance of localized excitation accompanied by nuclear motion, bond distortion and vibration, as well as a minor contribution from delocalized plasmonic excitation. The significance of coupled electron–ion dynamics in modulating the irradiation processes is identified from comparative studies on the spatial and temporal patterns of excitation for unconstrained and constrained lattices. The stopping power or energy deposition is also calculated, quantifying the dissipative nature of charge density excitation. This study offers fundamental understandings of the single-particle irradiation effects on optoelectronic devices constructed from low-dimensional materials, and inspires unconventional techniques to excite the electrons and ions in a controllable way.
Proton RBE models: commonalities and differences
Authors: McMahon Stephen J 
Published: January 2021

Abstract
Uncertainties in the relative biological effectiveness (RBE) of protons remains a major barrier to the biological optimisation of proton therapy. While a constant value of 1.1 is widely used in treatment planning, extensive preclinical in vitro and in vivo data suggests that proton RBE is variable, depending on proton energy, target tissue, and endpoint. A number of phenomenological models have been developed to try and explain this variation, but agreement between these models is often poor. This has been attributed to both the models’ underlying assumptions and the data to which they are fit. In this brief note, we investigate the underlying trends in these models by comparing their predictions as a function of relevant biological and physical parameters, to determine where models are in conceptual agreement or disagreement. By doing this, it can be seen that the primary differences between models arise from how they handle biological parameters (i.e.

α

and

β

from the linear–quadratic model for photon exposures). By contrast, when specifically explored for linear energy transfer-dependence, all models show extremely good correlation. These observations suggest that there is a pressing need for more systematic exploration of biological variation in RBE across different cells in well-controlled conditions to help distinguish between these different models and identify the true behaviour.
Helical toroid phantom for 3D flow imaging investigations
Authors: Chee Adrian J Y , Ishii Takuro , Yiu Billy Y S , Yu Alfred C H 
Published: January 2021

Abstract
The medical physics community has hitherto lacked an effective calibration phantom to holistically evaluate the performance of three-dimensional (3D) flow imaging techniques. Here, we present the design of a new omnidirectional, three-component (3-C) flow phantom whose lumen is consisted of a helical toroid structure (4 mm lumen diameter; helically winded for 5 revolutions over a torus with 10 mm radius; 5 mm helix radius). This phantom’s intraluminal flow trajectory embraces all combinations of x, y, and z directional components, as confirmed using computational fluid dynamics (CFD) simulations. The phantom was physically fabricated via lost-core casting with polyvinyl alcohol cryogel (PVA) as the tissue mimic. 3D ultrasound confirmed that the phantom lumen expectedly resembled a helical toroid geometry. Pulsed Doppler measurements showed that the phantom, when operating under steady flow conditions (3 ml s−1 flow rate), yielded flow velocity magnitudes that agreed well with those derived from CFD at both the inner torus (−47.6 ± 5.7 versus −52.0 ± 2.2 cm s−1; mean ± 1 S.D.) and the outer torus (49.5 ± 4.2 versus 48.0 ± 1.7 cm s−1). Additionally, 3-C velocity vectors acquired from multi-angle pulsed Doppler showed good agreement with CFD-derived velocity vectors (<7% and 10° difference in magnitude and flow angle, respectively). Ultrasound color flow imaging further revealed that the phantom’s axial flow pattern was aligned with the CFD-derived flow profile. Overall, the helical toroid phantom has strong potential as an investigative tool in 3D flow imaging innovation endeavors, such as the development of flow vector estimators and visualization algorithms.
Regional lung function measures determined by electrical impedance tomography during repetitive ventilation manoeuvres in patients with COPD
Authors: Lasarow L , Vogt B , Zhao Z , Balke L , Weiler N , Frerichs I 
Published: January 2021

Abstract

Objective. Current standards for conducting spirometry examinations recommend that the ventilation manoeuvres needed in pulmonary function testing are carried out repeatedly during sessions. Chest electrical impedance tomography (EIT) can determine the presence of ventilation heterogeneity during such manoeuvres, which increases the information content derived from such examinations. The aim of this study was to characterise regional lung function in patients with chronic obstructive pulmonary disease (COPD) during repetitive forced full ventilation manoeuvres. Regional lung function measures derived from these manoeuvres were compared with quiet tidal breathing. Approach. Sixty hospitalised patients were examined during up to three repeated ventilation manoeuvres. Acceptable spirometry manoeuvres were performed and EIT recordings suitable for analysis obtained in 53 patients (12 women, 41 men; age: 68 ± 12 years (mean ± SD)). Pixel values of tidal volume, forced full inspiratory and expiratory volume in 1 s, and forced inspiratory and expiratory vital capacity were calculated from the EIT data. Spatial ventilation heterogeneity was assessed using the coefficient of variation, global inhomogeneity index, and centres and regional fractions of ventilation. Temporal inhomogeneity was determined by examining the pixel expiration times needed to exhale 50% and 75% of regional forced vital capacity. Main results. All EIT-derived measures of regional lung function showed reproducible results during repetitive examinations. Parameters of spatial heterogeneity obtained from quiet tidal breathing were comparable with the measures derived from the forced manoeuvres. Significance. Measures of spatial and temporal ventilation heterogeneity obtained in COPD patients by EIT provide comparable findings during repeated examinations within one testing session. Quiet tidal breathing generates similar information on ventilation heterogeneity as forced manoeuvres that demand a high amount of patient effort.
Ultrasound imaging for assessing functions of the GI tract
Authors: Steinsvik Elisabeth K , Hatlebakk Jan Gunnar , Hausken Trygve , Nylund Kim , Gilja Odd Helge 
Published: January 2021

Abstract

Objective. In the following review we outline how ultrasound can be used to measure physiological processes in the gastrointestinal tract. Approach. We have investigated the potential of ultrasound in assessing gastrointestinal physiology including original research regarding both basic methodology and clinical applications. Main results. Our main findings show the use of ultrasound to study esophageal motility, measure volume and contractility of the stomach, assess motility, wall thickness, and perfusion of the small bowel, and evaluate wall vascularization and diameters of the large bowel. Significance. Ultrasound is a widely accessible technology that can be used for both scientific and clinical purposes. Being radiation-free and user friendly, the examination can be frequently repeated enabling longitudinal studies. Furthermore, it does not influence normal GI physiology, thus being useful to estimate motility and subtle changes in physiology. Accordingly, ultrasound scanning and physiological measurements may make a big difference for the scientist and the doctor; and for the patients who receive an efficient work-up.
Numerical simulation of the hot-tail runaway electron production mechanism using CQL3D and comparison with Smith–Verwichte analytical model
Authors: Petrov Yu V , Parks P B , Harvey R W 
Published: January 2021

Abstract
The hot-tail mechanism of runaway electron (RE) production (Harvey et al 2000 Phys. Plasmas
7 4590) is the primary source of RE in the case of rapidly cooling tokamak plasma. Quantifying this mechanism is very important as it can provide most of the post-thermal-quench (TQ) current, or a seed current for the secondary source of RE through the avalanche mechanism. An analytic model which omits pitch-angle scattering is often used in literature for estimating the hot-tail RE density (Smith and Verwichte 2008 Phys. Plasmas
15 072502). In the present study, we use the CQL3D bounce-averaged Fokker–Planck code (Harvey and McCoy 1992 Proc. IAEA Technical Committee Meeting on Advances in Simulation and Modeling of Thermonuclear Plasmas p 527) to test the limits of validity of the model. In particular, we examine the cases of Z= 1 and Z= 18 ions, for sets of different initial temperature, density, electric field and the characteristic time of temperature decay. We show that for Z = 1 plasma, the ratio of RE density computed by CQL3D to that estimated from the model is within 0.6–6.0 in studied cases. For the Z = 18 case, this factor is systematically a much smaller number, typically 0.02–0.6. We suggest a simple correction to the model that narrows down the range of this ratio to 0.3–3.8 in all of the cases, including Z = 1 and Z = 18 plasmas.