bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhomogeneous magnetic properties characterized by simultaneous electrical and optical detection of spin-torque ferromagnetic resonance
Authors: Shiota Yoichi , Hisatomi Ryusuke , Moriyama Takahiro , Samardak Alexander S. , Ono Teruo
Published: November 2021

Magnetic properties of the Pt/Py microstrip were investigated using the simultaneous electrical and optical detection of spin-torque ferromagnetic resonance. From the measured optical signal using the heterodyne-magneto-optical Kerr effect (MOKE), we found that the inhomogeneous broadening and Gilbert damping constant were modified along the transverse direction of the microstrip. In addition, a difference in the precession phase was also observed owing to the non-uniform out-of-plane microwave field. Our study shows that the ferromagnetic resonance measurement based on the heterodyne-MOKE technique is a powerful tool for characterizing the static and dynamic magnetic properties of magnetic thin films with sub-micrometer spatial resolution.
Finite deformation of a random array of rigid spheres in an elastic matrix at high concentration
Authors: Phan-Thien (Phan Thiên Nhân) N. , Kim S. , Wang S.
Published: November 2021

We consider some modifications to the linear elastic deformation of an array of rigid spheres in an elastic medium to include an affine but finite displacement of the sphere, up to but not including elastic contact stresses between them. The subsequent and constitutive problem involves the load transfer problems between the spheres and illustrates the linkages between the microstructures and the macro-finite deformation stress incurred at the macro-level. The results represent a new class of finite deformation brought about by an array of rigid spheres in an otherwise perfectly elastic matrix.
Dynamics of a single cavitation bubble near a cylindrical rod
Authors: Kadivar Ebrahim , Phan Thanh-Hoang , Park Warn-Gyu , el Moctar Ould
Published: November 2021

In this study, we studied the dynamics of a laser-induced single cavitation bubble near a rigid cylindrical rod. We experimentally and numerically investigated the effects of the cylindrical rod on the dynamics of the growth and collapse of the single bubble at different relative wall distances. First, we performed the experiments using a high-speed camera to analyze the shape of the bubble collapse qualitatively. Second, we performed a numerical simulation using a fully compressible two-phase mixture model and an interface capturing scheme to analyze the dynamics of the single cavitation bubble. We analyzed different quantitative parameters, such as maximum velocity of the microjet and the pressure impact load for the bubble at various relative wall distances. The results showed that the bubble dynamics collapsing near the cylindrical rod differed significantly from the single bubble collapse near solid flat plates. A shape of mushroom can be formed during the collapse of the single bubble near the cylindrical rod at the smaller relative wall distances, such as γ = 0.3, 0.4, and 0.5. This mushroom-shaped bubble was not observed for the cases near the solid flat plates in the previous research or near the higher relative wall distances in our present results. In addition, our numerical results revealed that a mushroom-shaped bubble for the cases γ = 0.4, 0.5, and 0.7 may induce a lower jet impact load near the solid surface compared with the case γ = 1.0 with an oval-shaped bubble near the solid boundary.
A direct numerical simulation study of skewed three-dimensional spatially evolving compressible mixing layer
Authors: Boukharfane R. , Er-raiy A. , Elkarii M. , Parsani M.
Published: November 2021

The turbulent flow of spatially developing and high-speed hydrogen/air mixing layers subject to small skew angle ζ is systematically investigated by means of direct numerical simulation. The present database features both detailed chemistry and detailed transport (i.e., Soret, Dufour, and bulk viscosity effects). The angle ζ measures the misalignment of the two asymptotic streams of fluid, whose interaction creates the turbulent mixing region. Numerical simulations have been carried out either in the absence of skewing, namely, perfectly parallel streams (ζ=0°), or in skew angles ζ=5°, 10°, and 15°. The streamwise evolution and the self-similar state of turbulence statistics of skewed cases are reported and compared to the unskewed and reference case. The present computations indicate that the transitional region and the fully developed turbulence region depends strongly on the degree of flow skewing at the inlet. In particular, we find that skewing yields faster growth of the inlet structures, thus leading to mixing enhancement. The underlying mechanisms responsible for turbulence modulation are analyzed through the transport equation of the Reynolds stresses. One possible perspective of the present work concerns the mixing control and a reliable comparison between the experiment, simulations, and turbulence modeling.
Longitudinal and transverse NMR relaxivities of Ln(III)-DOTA complexes: A comprehensive investigation
Authors: Cicolari Davide , Santanni Fabio , Grassi Leonardo , Brero Francesca , Filibian Marta , Recca Teresa , Arosio Paolo , Perfetti Mauro , Mariani Manuel , Sessoli Roberta , Lascialfari Alessandro
Published: November 2021

Longitudinal and transverse 1H nuclear magnetic resonance relaxivities of Ln(III)-DOTA complexes (with Ln = Gd, Tb, Dy, Er; DOTA = 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid) and Mn(II) aqueous solutions were measured in a wide range of frequencies, 10 kHz to 700 MHz. The experimental data were interpreted by means of models derived from the Solomon–Bloembergen–Morgan theory. The data analysis was performed assuming the orbital angular momentum L = 0 for Gd-DOTA and the aqua ion [Mn(H2O)6]2+ and L ≠ 0 for Dy-, Tb-, and Er-DOTA. A refined estimation of the zero-field-splitting barrier Δ and of the modulation correlation time τv was obtained for [Mn(H2O)6]2+ by extending the fitting of nuclear magnetic relaxation dispersion profiles to the low-field regime. The Gd-DOTA fitting parameters resulted in good agreement with the literature, and the fit of transverse relaxivity data confirmed the negligibility of the scalar interaction in the nuclear relaxation mechanism. Larger transverse relaxivities of Dy-DOTA and Tb-DOTA (∼10 mM−1 s−1) with respect to Er-DOTA (∼1 mM−1 s−1) were observed at 16 T. Such higher values are suggested to be due to a shorter residence time τm that is possibly linked to the fluctuations of the hyperfine interaction and the different shape of the magnetic anisotropy. The possible employment of Dy-DOTA, Tb-DOTA, and Er-DOTA as negative magnetic resonance imaging contrast agents for high-field applications was envisaged by collecting spin-echo images at 7 T. Particularly in Dy- and Tb-derivatives, the transverse relaxivity at 16 T is of the order of the Gd-one at 1.5 T.
The rise and fall of branching: A slowing down mechanism in relaxing wormlike micellar networks
Authors: Baiesi Marco , Iubini Stefano , Orlandini Enzo
Published: November 2021

A mean-field kinetic model suggests that the relaxation dynamics of wormlike micellar networks is a long and complex process due to the problem of reducing the number of free end-caps (or dangling ends) while also reaching an equilibrium level of branching after an earlier overgrowth. The model is validated against mesoscopic molecular dynamics simulations and is based on kinetic equations accounting for scission and synthesis processes of blobs of surfactants. A long relaxation time scale is reached with both thermal quenches and small perturbations of the system. The scaling of this relaxation time is exponential with the free energy of an end cap and with the branching free energy. We argue that the subtle end-recombination dynamics might yield effects that are difficult to detect in rheology experiments, with possible underestimates of the typical time scales of viscoelastic fluids.
All-optical switch based on PbS quantum dots
Authors: Bhowmick Mithun , Singh Akhilesh Kumar , Barik Puspendu , Xi Haowen , Ullrich Bruno
Published: November 2021

We hetero-paired a ∼200 nm thin film consisting of colloidal 2.5 nm PbS quantum dots deposited on semi-insulating GaAs. By exciting the thin film with laser pulses (26 ps, 10 Hz) at 1064 nm, we observed the two-photon stimulated emission of the PbS quantum dots and the GaAs host. At a certain intensity of the optical stimulus, the absorption capability of the quantum dots collectively saturates, and more photons of the laser beam reach the GaAs host, causing a bistable-like up-switch in the GaAs photoluminescence intensity. The work further addresses the determination of the two-photon absorption coefficient, which was found to be 8.6 × 10−6 m/W.
Notched-ring structured microfluidic contact lens for intraocular pressure monitoring
Authors: Yang Wentuo , Zhang Xiaoshuang , Wang Yan , Fan Qian , Zhang Shuaihua , Chen Yongqi , Shen Xiaotian , Xie Mengying , Duan Xuexin
Published: November 2021

Microfluidic contact lenses (MCLs) for continuous intraocular pressure (IOP) monitoring are promising devices for the diagnosis and management of glaucoma. Here, we present an ultra-sensitive and cost-effective MCL for IOP monitoring. A folding method that allows 2D-to-3D transformation of a planar microchannel is introduced. An ultra-sensitive serpentine microchannel of notched-ring configuration is designed in coordination with the folding method. The optimization of the microchannel geometry is performed through numerical simulations and experiments. The performance of the device is evaluated using a hemispherical silicone model eye. The sensitivity of the MCL reaches up to 0.825°/μl, which clearly exceeds the existing MCLs. Moreover, stair-case and cyclical tests are performed to confirm the device's recoverability and repeatability. These results prove that the proposed MCL is a suitable selection for intraocular pressure monitoring.
Different SP1 binding dynamics at individual genomic loci in human cells
Authors: Hasegawa Yuko , Struhl Kevin
Published: November 2021

Significance

Transcription factor binding to target DNA sequences is critical for regulating gene expression in response to environmental and developmental cues. SP1 is a transcriptional activator protein that binds GC-box DNA sequences at many promoter and enhancer regions. Here, we use an inducible time-course ChIP-seq method to analyze SP1 binding dynamics at target sites throughout the human genome. SP1 rapidly reaches maximal binding levels at some sites, but binding kinetics at other sites is biphasic, with rapid half-maximal binding followed by a considerably slower increase to maximal binding. We describe the molecular parameters that distinguish between these different classes of SP1 binding sites. The biphasic kinetics at some SP1 sites suggests distinct chromatin states in different cells within the overall population.
Variational formalism for generic shells in general relativity
Authors: Racskó Bence
Published: November 2021

We investigate the variational principle for the gravitational field in the presence of thin shells of completely unconstrained signature (generic shells). Such variational formulations have been given before for shells of timelike and null signatures separately, but so far no unified treatment exists. We identify the shell equation as the natural boundary condition associated with a broken extremal problem along a hypersurface where the metric tensor is allowed to be nondifferentiable. Since the second order nature of the Einstein–Hilbert action makes the boundary value problem associated with the variational formulation ill-defined, regularization schemes need to be introduced. We investigate several such regularization schemes and prove their equivalence. We show that the unified shell equation derived from this variational procedure reproduce past results obtained via distribution theory by Barrabès and Israel for hypersurfaces of fixed causal type and by Mars and Senovilla for generic shells. These results are expected to provide a useful guide to formulating thin shell equations and junction conditions along generic hypersurfaces in modified theories of gravity.
A novel mechanism for probing the Planck scale
Authors: Das Saurya , Modak Sujoy K
Published: November 2021

The Planck or the quantum gravity (QG) scale, being 16 orders of magnitude greater than the electroweak scale, is often considered inaccessible by current experimental techniques. However, it was shown recently by one of the current authors that QG effects via the generalized uncertainty principle affects the time required for free wavepackets to double their size, and this difference in time is at or near current experimental accuracies (Villalpando C and Modak S K 2019 Class. Quantum
Grav.

36 215016; Villalpando C and Modak S K 2019 Phys. Rev. D

100 024054). In this work, we make an important improvement over the earlier study, by taking into account the leading order relativistic correction, which naturally appears in the systems under consideration, due to the significant mean velocity of the travelling wavepackets. Our analysis shows that although the relativistic correction adds nontrivial modifications to the results of (Villalpando and Modak 2019 Class. Quantum Grav.

36 215016; Villalpando and Modak 2019 Phys. Rev. D

100 024054), the earlier claims remain intact and are in fact strengthened. We explore the potential for these results being tested in the laboratory.
A noniterative reconstruction method for solving a time-fractional inverse source problem from partial boundary measurements
Authors: Prakash R , Hrizi M , Novotny A A
Published: November 2021

In this paper, a noniterative method for solving an inverse source problem governed by the two-dimensional time-fractional diffusion equation is proposed. The basic idea consists in reconstructing the geometrical support of the unknown source from partial boundary measurements of the associated potential. A Kohn–Vogelius type shape functional is considered together with a regularization term penalizing the relative perimeter of the unknown set of anomalies. Identifiability result is derived and uniqueness of a minimizer is ensured. The shape functional measuring the misfit between the solutions of two auxiliary problems containing information about the boundary measurements is minimized with respect to a finite number of ball-shaped trial anomalies by using the topological derivative method. In particular, the second-order topological gradient is exploited to devise an efficient and fast noniterative reconstruction algorithm. Finally, some numerical experiments are presented, showing different features of the proposed approach in reconstructing multiple anomalies of varying shapes and sizes by taking noisy data into account.
Preparation of arsenene and its applications in sensors
Authors: Zhou Rong , Xu Na , Guo Ranran , Ling Guixia , Zhang Peng
Published: November 2021

As an element of the graphene family, arsenic has attracted extensive attention due to its excellent photoelectric and transport properties. Arsenene conforms to an eight-electron coordination and spontaneously forms a wavy two-dimensional (2D) structure, which is more stable than other 2D materials. The adjustable bandgap makes it stand out from many 2D materials, and its unique semiconductor properties make it widely used in field-effect transistors. In recent years, different subtypes of arsenene have gradually been discovered. Due to their special gas-response characteristics, arsenenes have great application potential as gas-sensitive materials or resistance elements in the field of sensors. Defective arsenic and arsenene modified by atoms provide more possibilities and creative solutions for gas sensing. In this paper, the properties, preparation methods, and applications of arsenene in sensing in recent years are reviewed. The advantages and disadvantages of arsenene are introduced, and the development prospect of arsenene is investigated.
Effect of Co and Mg doping at Cu site on structural, magnetic and dielectric properties of α–Cu2V2O7
Authors: Kar Abja Keshar , Chattopadhyay Bidisa , Singha Ratnadwip , Barman Abhisikta , Ahmed Md A , Midya A , Bandyopadhyay S , Mukherjee Devajyoti , Jana D , Mandal Prabhat
Published: November 2021

We have studied the effect of doping of both magnetic (Co) and nonmagnetic (Mg) ions at the Cu site on phase transition in polycrystalline α–Cu2V2O7 through structural, magnetic, and electrical measurements. X-ray diffraction reveals that Mg doping triggers an onset of α- to β-phase structural transition in Cu2−x
Mg
x
V2O7 above a critical Mg concentration x
c = 0.15, and both the phases coexist up to x = 0.25. Cu2V2O7 possesses a non-centrosymmetric crystal structure and antiferromagnetic ordering along with a non-collinear spin structure in the α phase, originated from the microscopic Dzyaloshinskii–Moriya interaction between the neighboring Cu spins. Accordingly, a weak ferromagnetic (FM) behavior has been observed up to x = 0.25. However, beyond this concentration, Cu2−x
Mg
x
V2O7 exhibits complex magnetic properties. A clear dielectric anomaly is observed in α–Cu2−x
Mg
x
V2O7 around the magnetic transition temperature, which loses its prominence with the increase in Mg doping. The analysis of experimental data shows that the magnetoelectric coupling is nonlinear, which is in agreement with the Landau theory of continuous phase transitions. Co doping, on the other hand, initiates a sharp α to β phase transition around the same critical concentration x
c = 0.15 in Cu2−x
Co
x
V2O7 but the FM behavior is very weak and can be detected only up to x = 0.10. We have drawn the magnetic phase diagram which indicates that the rate of suppression in transition temperature is the same for both types of doping, magnetic (Co) and nonmagnetic (Zn/Mg).
Adaptive multiple second-order synchrosqueezing wavelet transform and its application in wind turbine gearbox fault diagnosis
Authors: Yu Zhaohong , Yi Cancan , Chen Xiangjun , Huang Tao
Published: November 2021

Wind turbines usually operate in harsh environments and in working conditions of variable speed, which easily causes their key components such as gearboxes to fail. The gearbox vibration signal of a wind turbine has nonstationary characteristics, and the existing time-frequency (TF) analysis (TFA) methods have some problems such as insufficient concentration of TF energy. In order to obtain a more apparent and more congregated time-frequency representation (TFR), this paper proposes a new TFA method, namely adaptive multiple second-order synchrosqueezing wavelet transform (AMWSST2). Firstly, a short-time window is innovatively introduced on the foundation of classical continuous wavelet transform, and the window width is adaptively optimized by using the center frequency and scale factor. After that, a smoothing process is carried out between different segments to eliminate the discontinuity and thus adaptive wavelet transform is generated. Then, on the basis of the theoretical framework of synchrosqueezing transform and accurate instantaneous frequency estimation by the utilization of second-order local demodulation operator, adaptive second-order synchrosqueezing wavelet transform (AWSST2) is formed. Considering that the quality of actual TFA is greatly disturbed by noise components, through performing multiple synchrosqueezing operations, the congregation of TFR energy is further improved, and finally, the AMWSST2 algorithm studied in this paper is proposed. Since synchrosqueezing operations are performed only in the frequency direction, this method AMWSST2 allows the signal to be perfectly reconstructed. For the verification of its effectiveness, this paper applies it to the processing of the vibration signal of the gearbox of a 750 kW wind turbine.
Electrochemical biosensor based on CuPt alloy NTs-AOE for the ultrasensitive detection of organophosphate pesticides
Authors: Yang Yunxia , Liu Qian , Zhao Yisong , Chen Jianmin , Chen Bing , Yan Yanling , Gao Faming
Published: November 2021

The electrode material is vital for the performance of the electrochemical biosensor. Lately, many nanomaterials have been developed to improve the sensitivity and detection efficiency of the biosensors. In this work, a kind of one-dimensional nanomaterials, the CuPt alloy nanotubes with an open end (CuPt alloy NTs-AOE), was explored. The nanotubes with an open end can provide a larger electrochemical active surface area and more active sites for the immobilization of enzyme. The CuPt alloy displays excellent conductivity and catalytic activity. In addition, the Cu shows the great affinity to thio-compounds, which can greatly enhance the detection efficiency and sensitivity. As a result, the prepared biosensor demonstrates the wider linear range of 9.98 × 10−10–9.98 × 10–5 g l−1 for fenitrothion and 9.94 × 10−11–9.94 × 10–4 g l−1 for dichlorvos (as model OPs ) and with the lower detection limit of 1.84 × 10–10 g l−1 and 6.31 × 10–12 g l−1 (S/N = 3), respectively. Besides, the biosensor has been used to detect the real samples and obtains satisfactory recoveries (95.58%–100.56%).
Effects of thermal annealing on the distribution of boron and phosphorus in p-i-n structured silicon nanocrystals embedded in silicon dioxide
Authors: Nomoto Keita , Cui Xiang-Yuan , Breen Andrew , Ceguerra Anna V , Perez-Wurfl Ivan , Conibeer Gavin , Ringer Simon P
Published: November 2021

Thermal annealing temperature and time dictate the microstructure of semiconductor materials such as silicon nanocrystals (Si NCs). Herein, atom probe tomography (APT) and density functional theory (DFT) calculations are used to understand the thermal annealing temperature effects on Si NCs grown in a SiO2 matrix and the distribution behaviour of boron (B) and phosphorus (P) dopant atoms. The APT results demonstrate that raising the annealing temperature promotes growth and increased P concentration of the Si NCs. The data also shows that the thermal annealing does not promote the incorporation of B atoms into Si NCs. Instead, B atoms tend to locate at the interface between the Si NCs and SiO2 matrix. The DFT calculations support the APT data and reveal that oxygen vacancies regulate Si NC growth and dopant distribution. This study provides the detailed microstructure of p-type, intrinsic, and n-type Si NCs with changing annealing temperature and highlights how B and P dopants preferentially locate with respect to the Si NCs embedded in the SiO2 matrix with the aid of oxygen vacancies. These findings will be useful towards future optoelectronic applications.
Synergetic modulation of surface alkali and oxygen vacancy over SrTiO3 for the CO2 photodissociation
Authors: Xu Hua , Yan Chunlei , Li Ruizhe , Song Lizhu , Ouyang Shuxin
Published: November 2021

Photochemical conversion of CO2 into solar fuels is one of the promising strategies to reducing the CO2 emission and developing a sustainable carbon economy. For the more efficient utilization of solar spectrum, several approaches were adopted to pursue the visible-light-driven SrTiO3. Herein, oxygen vacancy was introduced over the commercial SrTiO3 (SrTiO3−x
) via the NaBH4 thermal treatment, to extend the light absorption and promote the CO2 adsorption over SrTiO3. Due to the mid-gap states resulted from the oxygen deficiency, combined with the intrinsic energy level of SrTiO3, the SrTiO3−x
catalyst exhibited excellent CO productivity (4.1 μmolˑg−1ˑh−1) and stability from the CO2 photodissociation under the visible-light irradiation (λ > 400 nm). Then, surface alkalization over SrTiO3−x
(OH-SrTiO3−x
) was carried out to further enhance the CO2 adsorption/activation over the surface base sites and provide the OH ions as hole acceptor, the surface alkali OH connected with Sr site of SrTiO3 could also weaken the Sr–O bonding thus facilitate the regeneration of surface oxygen vacancy under the light illumination, thus resulting in 1.5 times higher CO productivity additionally. This study demonstrates that the synergetic modulation of alkali OH and oxygen vacancy over SrTiO3 could largely promote the CO2 photodissociation activity.
Persistence of lower dimensional degenerate invariant tori with prescribed frequencies in Hamiltonian systems with small parameter
Authors: Xu Junxiang
Published: November 2021

In this paper we develop some KAM techniques to prove the persistence of lower dimensional elliptic-type degenerate invariant tori with prescribed frequencies in Hamiltonian systems. The proof is based on a formal KAM theorem, which allows us to solve the equation of equilibrium points and choose the parameter of small divisors after the KAM iteration, instead of in each KAM step. The proof is also based on the Leray–Schauder continuation theorem, which insures the existence of a path of real roots of an approximating odd-order real polynomial which depends continuously on parameters. This result is very important for us to tackle the Melnikov condition in the elliptic-type degenerate case.
Capturing the cascade: a transseries approach to delayed bifurcations
Authors: Aniceto Inês , Hasenbichler Daniel , Howls Christopher J , Lustri Christopher J
Published: November 2021

Transseries expansions build upon ordinary power series methods by including additional basis elements such as exponentials and logarithms. Alternative summation methods can then be used to ‘resum’ series to obtain more efficient approximations, and have been successfully widely applied in the study of continuous linear and nonlinear, single and multidimensional problems. In particular, a method known as transasymptotic resummation can be used to describe continuous behaviour occurring on multiple scales without the need for asymptotic matching. Here we apply transasymptotic resummation to discrete systems and show that it may be used to naturally and efficiently describe discrete delayed bifurcations, or ‘canards’, in singularly-perturbed variants of the logistic map which contain delayed period-doubling bifurcations. We use transasymptotic resummation to approximate the solutions, and describe the behaviour of the solution across the bifurcations. This approach has two significant advantages: it may be applied in systematic fashion even across multiple bifurcations, and the exponential multipliers encode information about the bifurcations that are used to explain effects seen in the solution behaviour.
Convergence of stochastic 2D inviscid Boussinesq equations with transport noise to a deterministic viscous system
Authors: Luo Dejun
Published: November 2021

The inviscid 2D Boussinesq system with thermal diffusivity and multiplicative noise of transport type is studied in the L
2-setting. It is shown that, under a suitable scaling of the noise, weak solutions to the stochastic 2D Boussinesq equations converge weakly to the unique solution of the deterministic viscous Boussinesq system. Consequently, the transport noise asymptotically regularises the inviscid 2D Boussinesq system and enhances dissipation in the limit.
Toward improved accuracy in shear wave elastography of arteries through controlling the arterial response to ultrasound perturbation in-silico and in phantoms
Authors: Hugenberg Nicholas R , Roy Tuhin , Harrigan Hadiya , Capriotti Margherita , Lee Hyoung-Ki , Guddati Murthy , Greenleaf James F , Urban Matthew W , Aquino Wilkins
Published: November 2021

Dispersion-based inversion has been proposed as a viable direction for materials characterization of arteries, allowing clinicians to better study cardiovascular conditions using shear wave elastography. However, these methods rely on a priori knowledge of the vibrational modes dominating the propagating waves induced by acoustic radiation force excitation: differences between anticipated and real modal content are known to yield errors in the inversion. We seek to improve the accuracy of this process by modeling the artery as a fluid-immersed cylindrical waveguide and building an analytical framework to prescribe radiation force excitations that will selectively excite certain waveguide modes using ultrasound acoustic radiation force. We show that all even-numbered waveguide modes can be eliminated from the arterial response to perturbation, and confirm the efficacy of this approach with in silico tests that show that odd modes are preferentially excited. Finally, by analyzing data from phantom tests, we find a set of ultrasound focal parameters that demonstrate the viability of inducing the desired odd-mode response in experiments.
Ion heat and parallel momentum transport by stochastic magnetic fields and turbulence
Authors: Chen Chang-Chun , Diamond P H , Tobias S M
Published: November 2021

The theory of turbulent transport of parallel momentum and ion heat by the interaction of stochastic magnetic fields and turbulence is presented. Attention is focused on determining the kinetic stress and the compressive energy flux. A critical parameter is identified as the ratio of the turbulent scattering rate to the rate of parallel acoustic dispersion. For the parameter large, the kinetic stress takes the form of a viscous stress. For the parameter small, the quasilinear residual stress is recovered. In practice, the viscous stress is the relevant form, and the quasilinear limit is not observable. This is the principal prediction of this paper. A simple physical picture is developed and shown to recover the results of the detailed analysis.
B2.5-Eunomia simulations of Magnum-PSI detachment experiments: II. Collisional processes and their relevance
Authors: Chandra Ray , de Blank Hugo J. , Diomede Paola , Westerhof Egbert
Published: November 2021

Detachment is achieved in Magnum-PSI by increasing the neutral background pressure in the target chamber using gas puﬃng. The plasma is studied using the B2.5 multi ﬂuid plasma code B2.5 coupled with Eunomia, a Monte Carlo solver for neutral species. This study focuses on the eﬀect of increasing neutral background pressure to the plasma volumetric loss of particle, momentum and energy. The plasma particle and energy loss almost linearly scale with the increase of neutral background pressure, while the momentum loss does not scale as strongly. Plasma recombination processes include molecular activated recombination (MAR), dissociative attachment, and atomic recombination. Atomic recombination, which includes radiative and three-body recombination, is the most relevant plasma process in reducing the particle ﬂux and, consequently, the heat ﬂux to the target. The low temperature where atomic recombination becomes dominant is achieved by plasma cooling via elastic H+-H2 collisions. The transport of vibrationally excited H2 molecules out of the plasma serves as an additional electron cooling channel with relatively small contribution. Additionally, the transport of highly vibrational H2 has a signiﬁcant impact in reducing the eﬀective MAR and dissociative attachment collision rates and should be considered properly. The relevancy of MAR and atomic recombination occupy separate electron temperature regimes, respectively, at Te = 1.5 eV and Te = 0.3 eV, with dissociative attachment being relevant in the intermediary. Plasma cooling via elastic H+-H2 collisions is eﬀective at Te ≤ 1 eV.
High-performance normally-off recessed tri-gate GaN MIS-FETs in micrometer scale
Authors: Tsai Chia-Jung , You Xin-Rong , Tsai Meng-Hsuan , Hsin Yue-Ming
Published: November 2021

In this study, a normally-off AlGaN/GaN metal–insulator–semiconductor field-effect transistor (MIS-FET) based on the combination of tri-gate and recessed MIS gate is fabricated and characterized. The recessed tri-gate MIS-FET is manufactured by micro-level trenches, defining the fin-shaped channel and improving the gate control capability. The recessed surface is cleaned by a diluted buffered oxide etch, HCl solution, and tetramethylammonium hydroxide treatment before a 20 nm Al2O3 deposition by atomic layer deposition. After deposition, post-deposition annealing was carried out. Recessed tri-gate MIS-FET demonstrates a high threshold voltage of 3.1 V, a high drain current of 1121 mA mm−1, and an on/off current ratio of 2 × 108. A smaller on-resistance of 5.4 Ω mm compared with recessed planar MIS-FET of 12.7 Ω mm is achieved. Besides, the devices show a low I–V hysteresis. All experimental results confirm micro-level trenches realize the advantages of the recessed tri-gate structures, which supports a promising technique to pursue the normally-off operation of GaN high electron mobility transistors.
General bounded corner states in two-dimensional off-diagonal Aubry–André–Harper model with flat bands
Authors: Chen Chao , Qi Lu , Xing Yan , Cui Wen-Xue , Zhang Shou , Wang Hong-Fu
Published: November 2021

We investigate the general bounded corner states in a two-dimensional off-diagonal Aubry–André–Harper square lattice model supporting flat bands. We show that for certain values of the nearest-neighbor hopping amplitudes, triply degenerate zero-energy flat bands emerge in this lattice system. Moreover, the two-dimensional off-diagonal Aubry–André–Harper model splits into isolated fragments and hosts some general bounded corner states, and the absence of the energy gap results in that these general bounded corner states are susceptible to disorder. By adding intracellular next-nearest-neighbor hoppings, two flat bands with opposite energies split off from the original triply degenerate zero-energy flat bands and some robust general bounded corner states appear in real-space energy spectrum. Our work shows a way to obtain robust general bounded corner states in the two-dimensional off-diagonal Aubry–André–Harper model by the intracellular next-nearest-neighbor hoppings.
Broadband coherent perfect absorption by cavity coupled to three-level atoms in linear and nonlinear regimes
Authors: Wang Liyong , Hu Jiangong , Du Jiajia , Di Ke
Published: November 2021

A broadband coherent perfect absorption (CPA) scheme consisting of an optical resonator coupled with three-level atoms excited by single cavity mode is proposed and analyzed. We show the output light field from the system is completely suppressed under specific conditions when the system is excited in linear and nonlinear regimes by two identical light fields from two ends of optical cavity. An analytical broadband CPA criterion for central and sideband excitations of cavity quantum electrodynamics system is derived in linear regime. Moreover, we show the resonant excitation criterion for CPA is greatly extended in nonlinear regime. A new type of bistability behavior is found. The output field intensity and the bistability curve can be well tuned by dynamically adjusting system parameters. Our results demonstrate that the CPA is quite universal, and it should be useful in a variety of applications in optical logic and optical communication devices.
Bound state solutions of the hyper-radial Klein-Gordon equation under the Deng-Fan potential by WKB and SWKB methods
Authors: Omugbe E , Osafile O E , Inyang E P , Jahanshir A
Published: November 2021

The energy levels of the Klein–Gordon equation in hyper-radial space under the Deng-Fan potential energy function are studied by the SWKB and WKB approximation methods. We obtained the analytic solution of the energy spectra and the ground state wave function in closed form. Furthermore, we obtained the energy equation corresponding to the Schrodinger equation by invoking the non-relativistic limit. The variations of the non-relativistic N-dimensional energy spectra with the potential parameters and radial quantum number are investigated. The energy levels are degenerate for

N
=

2
,

N
=
4

and increase with the dimensionality number. The ground state wave function and its gradient are continuous at the boundary

r
=
0
,
r
=
∞
.

Our results for the energy spectra are in excellent agreement with the ones obtained by other analytical methods where similar centrifugal approximations were applied.
Self-organized multiscale structures in thermally relativistic electron-positron-ion plasmas
Authors: Shazad Usman , Iqbal M , Ullah Shafa
Published: November 2021

The self-organization of a thermally relativistic magnetized plasma comprising of electrons, positrons and static ions is investigated. The self-organized state is found to be the superposition of three distinct Beltrami fields known as triple Beltrami (TB) state. In general, the eigenvalues associated with the multiscale self-organized vortices may be a pair of complex conjugate and real one. It is shown that all the eigenvalues become real when thermal energy increases or the positron density decreases. The impact of relativistic temperature and positron density on the formation of self-organized structures is investigated. The self-organized field and flow vortices may vary simultaneously on vastly different length scales. The disparate variation of self-organized vortices is important in the context of dynamo theory. The present work is useful to study the formation of multiscale vortices and dynamo mechanisms in multi-species thermally relativistic plasmas.
Bi-funtional resonance effects of plasmon-induced transparency and Fano-like response using an asymmetry metamaterial resonator consisting of three metallic strips at terahertz frequency
Authors: Yang Zhuchuang , Wu Yangkuan , Xu Wei , Zhu Huaxin , Zhang Xiangyang , Wang Ben-Xin
Published: November 2021

Bi-functional metamaterial resonance device operated at terahertz frequency is designed in this paper. It is composed of three metallic strips, in which two parallel metallic strips having the identical dimensions are arranged in the longitudinal direction, and a single metallic strip deviated from the center position is arranged in the horizontal direction. Bi-functional resonance effects of plasmon-induced transparency (PIT) and Fano-like response are simultaneously obtained in this simple metamaterial structure. The formation mechanisms of the two resonance effects are analyzed with the aid of the near-field distributions and the dependence of structure parameters on the whole resonance performance. Results further show that the metallic strip placed horizontally plays an important role in adjusting the resonance response of the metamaterial resonator. More importantly, when the deviation value of the metallic strip in the horizontal direction exceeds a certain amount, for example 10 μm, the metamaterial resonator can realize the effective regulation from bi-functional resonance to single-functional PIT effect. Our proposed structure can be used as valuable platform for ideas to inspire the design of novel electro-optic devices.
Group velocity dispersion of a multicore fibre with 5 × 5 coupled cores for in-phase and out-of-phase supermodes
Authors: Andrianov A V , Kalinin N A , Anashkina E A
Published: November 2021

In-phase and out-of-phase supermodes were selectively excited (with modal content >90%) in the wavelength range near 1030 nm in a silica multicore fibre with 5 × 5 coupled cores using a spatial light modulator. Group velocity dispersion (GVD) parameters of 21 ps2 km−1 and 14 ps2 km−1 at 1030 nm were measured for in-phase and out-of-phase supermodes, respectively, using an interferometric scheme. The numerically simulated GVD values agree with the experimental results. The calculated zero-dispersion wavelengths (ZDWs) of 1360 nm and 1180 nm for in-phase and out-of-phase supermodes are red-shifted and blue-shifted, respectively, compared to the ZDW of silica glass. The anomalous dispersion for the out-of-phase supermode is predicted in the telecommunication O-band near 1300 nm. The theoretical explanation of the difference in the wavelength-dependence of GVD for in-phase and out-of-phase supermodes is given.
The Precursor Phase of an X-class Flare: Magnetic Reconnection, Powering and Non-thermal Electrons
Authors: Shen Jinhua , Ji Haisheng , Su Yingna
Published: November 2021

In this paper, we report three interesting phenomena that occurred during the precursor phase of the X1.6 class flare on 2014 September 10. (1) The magnetic reconnection initiating the flare occurs between one of the two J-shaped magnetic flux ropes that constitute a sigmoidal structure and the overlying sheared magnetic arcade that runs across the sigmoid over its middle part. The reconnection formed an erupting structure that ultimately leads to flare onset. Another J-shaped magnetic flux rope remains unaffected during the whole eruption. The phenomenon is revealed by the observation made by the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory (SDO) at 94 and 131 Å. (2) Being simultaneously with starting time of the precursor, photospheric vertical electric current (VEC) around the footpoint region of the overlying magnetic arcade underwent an obvious increase, as observed by the Helioseismic and Magnetic Imager (HMI) on board SDO. By only taking into account the VEC with current density over 3σ value (1σ: 10 mA m−2), we are able to pick out precursor-associated VEC increase starting from nearly the level of zero. We regard it as a kind of powering process for the magnetic reconnection between the two magnetic loops. (3) With high-resolution narrow-band Helium 10830 Å images taken by Goode Solar Telescope at Big Bear Solar Observatory (BBSO), we observe a narrow absorption (dark) front that runs along the erupting magnetic structure (or the erupting hot channel) and moves in the direction of the eruption during the precursor phase. Assuming the excitation mechanism of Helium atoms along the absorption front by non-thermal electrons, the phenomenon shows that the interaction between the erupted hot channel and the overlying (or surrounding) magnetic field has yielded electron acceleration.
Epitaxial growth of CsPbBr3/PbS single-crystal film heterostructures for photodetection
Authors: Wang Yifan , Li Xuanze , Liu Pei , Xia Jing , Meng Xiangmin
Published: November 2021

Epitaxial high-crystallization film semiconductor heterostructures has been proved to be an effective method to prepare single-crystal films for different functional devices in modern microelectronics, electro-optics, and optoelectronics. With superior semiconducting properties, halide perovskite materials are rising as building blocks for heterostructures. Here, the conformal vapor phase epitaxy of CsPbBr3 on PbS single-crystal films is realized to form the CsPbBr3/PbS heterostructures via a two-step vapor deposition process. The structural characterization reveals that PbS substrates and the epilayer CsPbBr3 have clear relationships: CsPbBr3(110) // PbS(100), CsPbBr3[

] // PbS[001] and CsPbBr3[001] // PbS[010]. The absorption and photoluminescence (PL) characteristics of CsPbBr3/PbS heterostructures show the broadband light absorption and efficient photogenerated carrier transfer. Photodetectors based on the heterostructures show superior photoresponsivity of 15 A/W, high detectivity of 2.65 × 1011 Jones, fast response speed of 96 ms and obvious rectification behavior. Our study offers a convenient method for establishing the high-quality CsPbBr3/PbS single-crystal film heterostructures and providing an effective way for their application in optoelectronic devices.
Radiation-hardened property of single-walled carbon nanotube film-based field-effect transistors under low-energy proton irradiation
Authors: Zhang Xiaorui , Zhu Huiping , Peng Song’ang , Xiong Guodong , Zhu Chaoyi , Huang Xinnan , Cao Shurui , Zhang Junjun , Yan Yunpeng , Yao Yao , Zhang Dayong , Shi Jingyuan , Wang Lei , Li Bo , Jin Zhi
Published: November 2021

Strong C–C bonds, nanoscale cross-section and low atomic number make single-walled carbon nanotubes (SWCNTs) a potential candidate material for integrated circuits (ICs) applied in outer space. However, very little work combines the simulation calculations with the electrical measurements of SWCNT field-effect transistors (FETs), which limits further understanding on the mechanisms of radiation effects. Here, SWCNT film-based FETs were fabricated to explore the total ionizing dose (TID) and displacement damage effect on the electrical performance under low-energy proton irradiation with different fluences up to 1 × 1015 p/cm2. Large negative shift of the threshold voltage and obvious decrease of the on-state current verified the TID effect caused in the oxide layer. The stability of the subthreshold swing and the off-state current reveals that the displacement damage caused in the CNT layer is not serious, which proves that the CNT film is radiation-hardened. Specially, according to the simulation, we found the displacement damage caused by protons is different in the source/drain contact area and channel area, leading to varying degrees of change for the contact resistance and sheet resistance. Having analyzed the simulation results and electrical measurements, we explained the low-energy proton irradiation mechanism of the CNT FETs, which is essential for the construction of radiation-hardened CNT film-based ICs for aircrafts.
Direct calculations on the band offsets of large-lattice-mismatched and heterovalent Si and III–V semiconductors
Authors: Hu Yuying , Qiu Chen , Shen Tao , Yang Kaike , Deng Huixiong
Published: November 2021

Band offset in semiconductors is a fundamental physical quantity that determines the performance of optoelectronic devices. However, the current method of calculating band offset is difficult to apply directly to the large-lattice-mismatched and heterovalent semiconductors because of the existing electric field and large strain at the interfaces. Here, we proposed a modified method to calculate band offsets for such systems, in which the core energy level shifts caused by heterovalent effects and lattice mismatch are estimated by interface reconstruction and the insertion of unidirectional strain structures as transitions, respectively. Taking the Si and III–V systems as examples, the results have the same accuracy as what is a widely used method for small-lattice-mismatched systems, and are much closer to the experimental values for the large-lattice-mismatched and heterovalent systems. Furthermore, by systematically studying the heterojunctions of Si and III–V semiconductors along different directions, it is found that the band offsets of Si/InAs and Si/InSb systems in [100], [110] and [111] directions belong to the type I, and could be beneficial for silicon-based luminescence performance. Our study offers a more reliable and direct method for calculating band offsets of large-lattice-mismatched and heterovalent semiconductors, and could provide theoretical support for the design of the high-performance silicon-based light sources.
Investigation of time domain characteristics of negative capacitance FinFET by pulse-train approaches
Authors: Cai Yuwei , Zhang Zhaohao , Zhang Qingzhu , Xiang Jinjuan , Xu Gaobo , Wu Zhenhua , Gu Jie , Yin Huaxiang
Published: November 2021

The HfO2-based ferroelectric field effect transistors (FeFET) have been widely studied for their ability in breaking the Boltzmann limit and the potential to be applied to low-power circuits. This article systematically investigates the transient response of negative capacitance (NC) fin field-effect transistors (FinFETs) through two kinds of self-built test schemes. By comparing the results with those of conventional FinFETs, we experimentally demonstrate that the on-current of the NC FinFET is not degraded in the MHz frequency domain. Further test results in the higher frequency domain show that the on-state current of the prepared NC FinFET increases with the decreasing gate pulse width at pulse widths below 100 ns and is consistently greater (about 80% with NC NMOS) than the on-state current of the conventional transistor, indicating the great potential of the NC FET for future high-frequency applications.