bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of sp–d exchange constants revisited
Authors: Andriotis Antonis N , Menon Madhu
Published: January 2021

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Ablated precursor plasma and evolution of magnetic field of exploding cylindrical thin liner
Authors: Zhang Daoyuan , Wu Jian , Chen Ziwen , Lu Yihan , Shi Huantong , Li Xingwen , Jia Shenli , Wang Guanqiong , Gan YunDan , Zhang Jiangbo
Published: January 2021

The formation of precursor plasma and ablation dynamics of Al thin liner explosion are investigated in this manuscript. The size of 12 mm in diameter, 10 μm in thickness Al liners are exploded on the Qin-1 facility (about 450 ns, 450 kA). An axial laser shadowgraphy and interferometry platform is set up to observe the plasma dynamics inside the liner. To solve the problem that the inside plasma density of the liner cannot be absolutely calibrated due to the lack of a zero plasma density area, we have established a CW laser interference system using a streak camera which can trace the interference lines over time. Low-density (10−7−10−6 g cm−3) precursor plasma is generated from the interior wall and flows towards the center with a velocity of about 150–200 km s−1, thus forming a column with high electron density by accumulation. Simultaneously, a high-density plasma layer flows toward the center at about 10 km s−1. The electron density of the central plasma column rises up rapidly after the precursor reaches the center and achieves 2.5 × 1018 cm−3 at 280 ns after the current starts. To fully understand the process, we have used the resistive magnetohydrodynamic code FLASH to realize a simulation to study interior precursor dynamics. We compared these simulation results with our experiments. Finally, we measured the voltage for the whole process and derived the inductance change and effective current radius. We compared the simulated current density distribution with the experimental result which proves that a considerable amount of current flows through the center plasma column, making the effective radius of current become smaller over time.
Single-shot 3D imaging of hydroxyl radicals in the vicinity of a gliding arc discharge
Authors: Bao Yupan , Dorozynska Karolina , Stamatoglou Panagiota , Kong Chengdong , Hurtig Tomas , Pfaff Sebastian , Zetterberg Johan , Richter Mattias , Kristensson Elias , Ehn Andreas
Published: January 2021

Plasma-related studies in gas phase are challenging to carry out due to plasma’s transient and unpredictable behavior, excessive luminosity emission, 3D complexity and aggressive chemistry and physiochemical interactions that are easily affected by external probing. Laser-induced fluorescence is a robust technique for non-intrusive investigations of plasma-produced species. In this letter, we present 3D distributions of ground state hydroxyl radicals (OH) radicals in the vicinity of a glow-type gliding arc plasma. Such radical distributions are captured instantaneously in one single camera acquisition by combining structured laser illumination and a lock-in based imaging analysis method called FRAME. The interference of plasma emission is automatically subtracted by the FRAME technique. In addition, the orientation of the plasma discharge can be reconstructed from the 3D data matrix, which can then be used to calculate 2D distributions of ground state OH radicals in a plane perpendicular to the orientation of the plasma channel. Our results indicate that OH distributions around a gliding arc are strongly affected by gas dynamics. We believe that the ability to instantaneously capture 3D transient molecular distributions in a plasma discharge, with minimal plasma emission interference, will have a strong impact on the plasma community for in situ investigations of plasma-induced chemistry and physics.
Two-dimensional oxygen functionalized honeycomb and zigzag dumbbell silicene with robust Dirac cones
Authors: Chen Xin , Li Linyang , Peeters François M , Sanyal Biplab
Published: January 2021

Dumbbell-like structures are recently found to be energetically favored in group IV two-dimensional (2D) materials, exhibiting rich physics and many interesting properties. In this paper, using first-principles calculations, we have investigated the oxidized form of the hexagonal honeycomb (ODB-h) and zigzag dumbbell silicene (ODB-z). We confirm that both oxidization processes are energetically favorable, and their phonon spectra further demonstrate the dynamic stability. Contrary to the pristine dumbbell silicene structures (PDB-h and PDB-z silicene), these oxidized products ODB-h and ODB-z silicene are both semimetals with Dirac cones at the Fermi level. The Dirac cones of ODB-h and ODB-z silicene are at the K point and between Y and Γ points respectively, possessing high Fermi velocities of 3.1 × 105 m s−1 (ODB-h) and 2.9–3.4 × 105 m s−1 (ODB-z). The origin of the Dirac cones is further explained by tight-binding models. The semimetallic properties of ODB-h and ODB-z are sensitive to compression due to the self-absorption effect, but quite robust against the tensile strain. These outstanding properties make oxidized dumbbell silicene a promising material for quantum computing and high-speed electronic devices.
Nonlinear localized modes in two-dimensional hexagonally-packed magnetic lattices
Authors: Chong Christopher , Wang Yifan , Maréchal Donovan , Charalampidis Efstathios G , Molerón Miguel , Martínez Alejandro J , Porter Mason A , Kevrekidis Panayotis G , Daraio Chiara
Published: January 2021

We conduct an extensive study of nonlinear localized modes (NLMs), which are temporally periodic and spatially localized structures, in a two-dimensional array of repelling magnets. In our experiments, we arrange a lattice in a hexagonal configuration with a light-mass defect, and we harmonically drive the center of the chain with a tunable excitation frequency, amplitude, and angle. We use a damped, driven variant of a vector Fermi–Pasta–Ulam–Tsingou lattice to model our experimental setup. Despite the idealized nature of this model, we obtain good qualitative agreement between theory and experiments for a variety of dynamical behaviors. We find that the spatial decay is direction-dependent and that drive amplitudes along fundamental displacement axes lead to nonlinear resonant peaks in frequency continuations that are similar to those that occur in one-dimensional damped, driven lattices. However, we observe numerically that driving along other directions results in asymmetric NLMs that bifurcate from the main solution branch, which consists of symmetric NLMs. We also demonstrate both experimentally and numerically that solutions that appear to be time-quasiperiodic bifurcate from the branch of symmetric time-periodic NLMs.
Characterizing spatially varying optical emissions in a steady-state dipole plasma: inversion based experiments and modeling
Authors: Bhattacharjee Sayak , Baitha Anuj Ram , Mathew Jose V , Bhattacharjee Sudeep
Published: January 2021

This study characterizes spatially varying optical emissions in a compact dipole plasma device driven at steady-state by continuous mode microwaves. The study is motivated by visual observations, which indicate a distinct pattern of alternate bright and less bright regions (bearing structural resemblance to the two particle radiation belts found in the Earth's magnetosphere). The investigation is performed in two experimental systems of cylindrical and spherical geometries, and boundary effects in the optical emissivity are observed in the smaller cylindrical system. Two optical diagnostic techniques are employed, namely, a simplistic linear inversion method, and the standard Abel inversion method, to invert the measured intensities and determine the local (spatially varying) emissivities in the equatorial plane of the dipole plasma. The study involves the design and development of the two optical probes, specifically, a telescopic probe capable of motion along a radial line (for linear inversion), and a mechanical gear-operated probe capable of bidirectional motion to obtain chord integrated intensities (for Abel inversion). Finally, the transition specific photon emission rates are determined by the application of a modified corona model, and the emission rates are compared with the experimental results. The existence of two bright belts separated by a darker band in the dipole plasma is confirmed by both the experimental and modeling results.
Pencil-like periodic ridges under second Bragg incidence as dual-function beam separation
Authors: Lin Zefan , Wang Bo
Published: January 2021

A reflective dual-function pencil-like grating under second Bragg incidence is proposed in this paper. The finite element analysis method is chosen to be the research technique of this grating. Based on it, the influence of the incident angle, period, duty cycle, incident wavelength, and other parameters on the diffraction efficiency are analyzed in detail. At an incident laser wavelength of 1.55 μm, for TE polarization, the efficiency of −2nd order is 96.57% so that the proposed grating can be regarded as a single-port high-efficiency reflective grating. For TM polarization, the grating can function as a dual-port grating with the efficiency 46.03% for 0th order and 45.96% for −2nd order. What is more, the proposed grating has a broader angular bandwidth compared with other dual-function gratings, which ensures the diffraction performance of the grating while allowing some operational changes.
Investigation of quark distributions in a family of pentaquarks using the Thomas–Fermi quark model
Authors: Giri Mohan , Baral Suman , Kaphle Gopi Chandra , Dangi Nirmal , Shiwakoti Sudip , Bardomero Leonardo , Lashomb Paul , Wilcox Walter
Published: January 2021

Using the Thomas–Fermi quark model, a collective, spherically symmetric density of states is created to represent a gas of interacting fermions with various degeneracies at zero temperature. Over a family of pentaquarks,

uudc

c

¯

, color interaction probabilities were obtained after averaging over all the possible configurations. Three different functions are developed for light, charm, and anti-charm quarks and are assumed to be linearly related by some proportionality constants. Interesting patterns of quark distributions are observed while analyzing the quark function consistency conditions for such constants.
Magnetohydrodynamic flow and heat transfer of a hybrid nanofluid over a rotating disk by considering Arrhenius energy
Authors: Reddy M Gnaneswara , R Naveen Kumar , Prasannakumara B C , Rudraswamy N G , Ganesh Kumar K
Published: January 2021

This research work explores the effect of hybrid nanoparticles on the flow over a rotating disk by using an activation energy model. Here, we considered molybdenum disulfide and ferro sulfate as nanoparticles suspended in base fluid water. The magnetic field is pragmatic normal to the hybrid nanofluid flow direction. The derived nonlinear ordinary differential equations are non-dimensionalized and worked out numerically with the help of Maple software by the RKF-45 method. The scientific results for a non-dimensionalized equation are presented for both nanoparticle and hybrid nanoparticle case. Accoutrements of various predominant restrictions on flow and thermal fields are scanned. Computation estimation for friction factor, local Nusselt number and Sherwood number are also executed. Results reveal that the reduction of the heat transfer rate is greater in hybrid nanoparticles when compared to nanoparticles for increasing values of Eckert Number and the thermal field enhances for the enhanced values of volume fraction.
Exploring the latest Pantheon SN Ia dataset by using three kinds of statistics techniques
Authors: Wang Shuang , Luo Xiaolin
Published: January 2021

In this work, we explore the cosmological consequences of the latest Type Ia supernova (SN Ia) dataset, Pantheon, by adopting the wCDM model. The Pantheon dataset currently contains the largest number of SN Ia samples, which contains 1048 supernovae on the redshift range 0 < z < 2.3. Here we take into account three kinds of SN Ia statistics techniques, including: (1) magnitude statistics (MS), which is the traditional SN Ia statistics technique; (2) flux statistics (FS), which is based on the flux-averaging (FA) method; and (3) improved flux statistics (IFS), which combines the advantages of MS and FS. It should be mentioned that the IFS technique needs to scan the (z
cut, Δz) parameters plane, where z
cut and Δz are redshift cut-off and redshift interval of FA, respectively. The results are as follows. (1) Using the SN dataset only, the best FA recipe for IFS is (z
cut, Δz) = (0.1, 0.08); (2) comparing to the old SN dataset, JLA, adopting the Pantheon dataset can reduce the 2σ error bars of equation of state w by 38%, 47% and 53% for MS, FS and IFS, respectively; (3) FS gives closer results to other observations, such as Baryon acoustic oscillations and cosmic microwave background; (4) compared with FS and IFS, MS more favors a Universe that will end in a ‘big rip’.
High-throughput identification of one-dimensional atomic wires and first principles calculations of their electronic states*
Authors: Lu Feng , Cui Jintao , Liu Pan , Lin Meichen , Cheng Yahui , Liu Hui , Wang Weichao , Cho Kyeongjae , Wang Wei-Hua
Published: January 2021

Low dimensional materials are suitable candidates applying in next-generation high-performance electronic, optoelectronic, and energy storage devices because of their uniquely physical and chemical properties. In particular, one-dimensional (1D) atomic wires (AWs) exfoliating from 1D van der Waals (vdW) bulks are more promising in next generation nanometer (nm) even sub-nm device applications owing to their width of few-atoms scale and free dandling bonds states. Although several 1D AWs have been experimentally prepared, few 1D AW candidates could be practically applied in devices owing to lack of enough suitable 1D AWs. Herein, 367 kinds of 1D AWs have been screened and the corresponding computational database including structures, electronic structures, magnetic states, and stabilities of these 1D AWs has been organized and established. Among these systems, unary and binary 1D AWs with relatively small exfoliation energy are thermodynamically stable and theoretically feasible to be exfoliated. More significantly, rich quantum states emerge, such as 1D semiconductors, 1D metals, 1D semimetals, and 1D magnetism. This database will offer an ideal platform to further explore exotic quantum states and exploit practical device applications using 1D materials. The database are openly available at http://www.dx.doi.org/10.11922/sciencedb.j00113.00004.
Effects of substitution of group-V atoms for carbon or silicon atoms on optical properties of silicon carbide nanotubes*
Authors: Yang Ying-Ying , Gong Pei , Ma Wan-Duo , Hao Rui , Fang Xiao-Yong
Published: January 2021

Silicon carbide nanotubes (SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs’ dopants.
Understanding the synergistic effect of mixed solvent annealing on perovskite film formation*
Authors: Qian Kun , Li Yu , Song Jingnan , Ali Jazib , Zhang Ming , Zhu Lei , Ding Hong , Zhan Junzhe , Feng Wei
Published: January 2021

Morphology control of perovskite films is of critical importance for high-performance photovoltaic devices. Although solvent vapor annealing (SVA) treatment has been widely used to improve the film quality efficiently, the detailed mechanism of film growth is still under construction, and there is still no consensus on the selection of solvents and volume for further optimization. Here, a series of solvents (DMF, DMSO, mixed DMF/DMSO) were opted for exploring their impact on fundamental structural and physical properties of perovskite films and the performance of corresponding devices. Mixed solvent SVA treatment resulted in unique benefits that integrated the advantages of each solvent, generating a champion device efficiency of 19.76% with improved humidity and thermal stability. The crystallization mechanism was constructed by conducting grazing-incidence wide-angle x-ray diffraction (GIWAXS) characterizations, showing that dissolution and recrystallization dominated the film formation. A proper choice of solvent and its volume balancing the two processes thus afforded the desired perovskite film. This study reveals the underlying process of film formation, paving the way to producing energy-harvesting materials in a controlled manner towards energy-efficient and stable perovskite-based devices.
Band alignment between NiO
x
and nonpolar/semipolar GaN planes for selective-area-doped termination structure*
Authors: Du Ji-Yao , Zhou Ji-Yu , Li Xiao-Bo , Pu Tao-Fei , Li Liu-An , Liu Xin-Zhi , Ao Jin-Ping
Published: January 2021

Band alignment between NiO
x
and nonpolar GaN plane and between NiO
x
and semipolar GaN plane are measured by x-ray photoelectron spectroscopy. They demonstrate that the maximum value of the valence band in the unintentional-doped a-plane, m-plane, and r-plane GaN are comparable to each other, which means that all the substrates are of n-type with similar background carrier concentrations. However, the band offset at the NiO
x
/GaN interface presents obvious crystalline plane dependency although they are coated with the same NiO
x
films. By fitting the Ga 3d spectrum obtained from the NiO
x
/GaN interface, we find that relatively high Ga–O content at the interface corresponds to a small band offset. On the one hand, the high Ga–O content on the GaN surface will change the growth mode of NiO
x
. On the other hand, the affinity difference between Ga and O forms a dipole which will introduce an extra energy band bending.
Tuning transport coefficients of monolayer MoSi2N4 with biaxial strain*
Authors: Guo Xiao-Shu , Guo San-Dong
Published: January 2021

Experimentally synthesized MoSi2N4 (Science
369 670 (2020)) is a piezoelectric semiconductor. Here, we systematically study the large biaxial (isotropic) strain effects (0.90–1.10) on electronic structures and transport coefficients of monolayer MoSi2N4 by density functional theory (DFT). With a/a
0 from 0.90 to 1.10, the energy band gap firstly increases, and then decreases, which is due to transformation of conduction band minimum (CBM). Calculated results show that the MoSi2N4 monolayer is mechanically stable in the considered strain range. It is found that the spin-orbital coupling (SOC) effects on Seebeck coefficient depend on the strain. In unstrained MoSi2N4, the SOC has neglected influence on Seebeck coefficient. However, the SOC can produce important influence on Seebeck coefficient, when the strain is applied, for example, 0.96 strain. The compressive strain can change relative position and numbers of conduction band extrema (CBE), and then the strength of conduction bands convergence can be enhanced, to the benefit of n-type ZT
e. Only about 0.96 strain can effectively improve n-type ZT
e. Our works imply that strain can effectively tune the electronic structures and transport coefficients of monolayer MoSi2N4, and can motivate farther experimental exploration.
Characteristic mode analysis of wideband high-gain and low-profile metasurface antenna*
Authors: Gao Kun , Cao Xiang-Yu , Gao Jun , Yang Huan-Huan , Han Jiang-Feng
Published: January 2021

A wideband high-gain and low-profile metasurface antenna is proposed by analyzing characteristic quantities and parameters in the characteristic modes (CMs). The detailed modal current and modal weighting coefficient are analyzed to explain the broadband operation and high gain. A dominant characteristic mode is well excited, leading to a broadband operation. The mode behaviors of the excitation are changed to suppress the unwanted higher-order modes and improve the radiation performance by changing the widths of two patches. The measured impedance bandwidth for –10 dB is 39.8% (5.3 GHz–7.94 GHz) with a gain of 7.8 dBi–10.04 dBi over the operating bandwidth.
A new calibration setup for lock-in amplifiers in the low frequency range and its validation in a bilateral comparison
Authors: Cultrera Alessandro , Corminboeuf David , D’Elia Vincenzo , Tran Ngoc Thanh Mai , Callegaro Luca , Ortolano Massimo
Published: January 2021

This paper addresses the calibration of lock-in amplifiers in the low frequency range. A simple but effective calibration setup implemented at INRIM is described. This includes a stable low-voltage source, composed of a digital sine wave generator and a cascade of two voltage dividers, one inductive and one resistive. The magnitude error is the lock-in magnitude error, which can be determined with an uncertainty of the order of 10−4 or better, that is, two orders of magnitude lower than the typical lock-in accuracy specification. The system can operate with an input voltage from 0.1 µV to 10 µV and a frequency from a few hertz to about 1 kHz. The performances of the calibration setup were evaluated at 1 µV and 10 μV at 20 Hz and 103 Hz and compared with those of another existing setup, implemented at METAS, through a direct comparison in the framework of an EURAMET research project.
Quasilinear critical gradient model for Alfven eigenmode driven energetic particle transport with intermittency
Authors: Waltz R.E. , Bass E.M. , Collins C.S. , Gage K.
Published: January 2021

A simplified quasilinear critical gradient model (QLCGM) for Alfven eigenmode (AE) driven energetic particle (EP) transport is used to treat the intermittency (burstiness) of the transport. Here intermittency is defined as the ratio of the root mean square deviation from mean flow to the mean flow. The model posits that the intermittency results from the micro-turbulent noise induced in the thermal plasma damping rate for the AE. The model is embedded in a time-dependent EP density transport code to generate the transport-flow time traces from typical critical gradient and slowing down density profiles. The QLCGM appears to be in reasonable agreement with the level and characteristics of the intermittency observed in the DIII-D fast particle loss detector flow time traces: high kurtosis [O(40)] of the burstiness with the intermittency O(1–2) increasing with the level of mean flow.
The updated ITPA global H-mode confinement database: description and analysis
Authors: Verdoolaege G. , Kaye S.M. , Angioni C. , Kardaun O.J.W.F. , Maslov M. , Romanelli M. , Ryter F. , Thomsen K. , ASDEX Upgrade Team the , EUROfusion MST1 Team the , Contributors JET
Published: January 2021

The multi-machine International Tokamak Physics Activity (ITPA) Global H-mode Confinement Database has been upgraded with new data from JET with the ITER-like wall and ASDEX Upgrade with the full tungsten wall. This paper describes the new database and presents results of regression analysis to estimate the global energy confinement scaling in H-mode plasmas using a standard power law. Various subsets of the database are considered, focusing on type of wall and divertor materials, confinement regime (all H-modes, ELMy H or ELM-free) and ITER-like constraints. Apart from ordinary least squares (OLS), two other, robust regression techniques are applied, which take into account uncertainty on all variables. Regression on data from individual devices shows that, generally, the confinement dependence on density and the power degradation are weakest in the fully metallic devices. Using the multi-machine scalings, predictions are made of the confinement time in a standard ELMy H-mode scenario in ITER. The uncertainty on the scaling parameters is discussed with a view to practically useful error bars on the parameters and predictions. One of the derived scalings for ELMy H-modes on an ITER-like subset is studied in particular and compared to the IPB98(y, 2) confinement scaling in engineering and dimensionless form. Transformation of this new scaling from engineering variables to dimensionless quantities is shown to result in large error bars on the dimensionless scaling. Regression analysis in the space of dimensionless variables is therefore proposed as an alternative, yielding acceptable estimates for the dimensionless scaling. The new scaling, which is dimensionally correct within the uncertainties, suggests that some dependencies of confinement in the multi-machine database can be reconciled with parameter scans in individual devices. This includes vanishingly small dependence of confinement on line-averaged density and normalized plasma pressure (β), as well as a noticeable, positive dependence on effective atomic mass and plasma triangularity. Extrapolation of this scaling to ITER yields a somewhat lower confinement time compared to the IPB98(y, 2) prediction, possibly related to the considerably weaker dependence on major radius in the new scaling (slightly above linear). Further studies are needed to compare more flexible regression models with the power law used here. In addition, data from more devices concerning possible ‘hidden variables’ could help to determine their influence on confinement, while adding data in sparsely populated areas of the parameter space may contribute to further disentangling some of the global confinement dependencies in tokamak plasmas.