bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of nitrogen flux and RF sputtering power on the preparation of crystalline a-plane AlN films on r-plane sapphire substrates
Authors: Cai Tingsong , Guo Yanan , Liu Zhibin , Zhang Ruijie , Xue Bin , Wang Chong , Liu Naixin , Yi Xiaoyan , Li Jinmin , Wang Junxi , Yan Jianchang 
Published: November 2022

Abstract

A-plane aluminum nitride (AlN) with high quality is crucial to fabricate high-performance non-polar deep-ultraviolet optoelectronic devices. In this work, we prepared crystalline a-plane AlN films on r-plane sapphire substrates by combining reactive magnetron sputtering and high temperature annealing (HTA). The effects of N2 flux and radio frequency (RF) sputtering power on the crystal quality, the surface morphology and the in-plane stress state of a-plane AlN films were comprehensively investigated. The results suggest that the properties of high temperature annealed a-plane AlN (HTA-AlN) films positively depend on the initial states of the sputtered AlN (SP-AlN) films. Increasing the N2 flux or the RF sputtering power can improve the crystalline quality of SP-AlN films by reducing the kinetic energy of deposited particles, which facilitates a-plane AlN deposition. A higher N2 flux smoothens the surface morphology due to the relieved bombardment effect, which is confirmed by the enlarged in-plane tensile stress state. However, a higher sputtering power leads to a rougher surface because of the accelerated deposition rate. With optimized sputtering parameters, a high-quality a-plane HTA-AlN template was obtained with full width at half maximum values of (11–20) plane x-ray rocking curves as low as 1188 and 1224 arcsec along [0001] and [1–100] directions, respectively. The surface presents an ordered stripe-like morphology with a root-mean-square value of 0.79 nm. Our work provides a convenient and effective strategy to prepare high quality a-plane AlN templates and accelerate the versatile application of non-polar deep-ultraviolet light-emitting diode devices.
Design and testing of a capacitive interface for underwater stretch sensors
Authors: Walker Christopher , Rosset Samuel , Anderson Iain 
Published: November 2022

Abstract
The growing popularity of wearable electronics has seen substantial research in soft and flexible strain sensors. From athletic performance analysis to human augmentation, there is a wide range of applications being developed. An area often overlooked is the connections between a network of wearable sensors and their measurement electronics. In dry applications this is as simple as cabling between the two. In underwater environments however this becomes more complicated. Capacitive strain sensors have been used to demonstrate underwater sensor-based motion capture in both a robotic fish and smart glove for divers. Wired connections introduced failure points and eliminated the modularity of the system for potted electronics. In this paper we have demonstrated the use of a capacitive interface as a wireless method to connect wearable strain sensors across an encapsulation to electronics. This removes the need to have wires permanently protruding through the encapsulation. The interfaces’ impact on strain sensor sensitivity and measurement method has been investigated for both resistive and capacitive-based strain sensing.
A frequency-dependent variable-damping control based variable-orifice damper for smart base-isolation system
Authors: Li Zhong-Xian , Wen Dongbin , Shi Yundong , Wei Xin 
Published: November 2022

Abstract
Damping devices are commonly used in the isolation layer of base-isolated structures to provide additional damping to control the structural responses. Normally, large damping for the isolation layer is useful to minimize the resonance effect under low-frequency ground motions, and small damping is preferred to reduce the structural responses under high-frequency ground motions. Traditional passive dampers are widely adopted in engineering practice. Due to the fixed damping characteristic, however, the performance of base-isolated structures with passive dampers cannot stay optimal under ground motions with different frequency characteristics. To realize an optimal control of base-isolated structures, semi-active control has been increasingly valued for its efficiency and intelligence to adjust the damping characteristics based on feedback information from the structure and ground motion. However, a large number of sensors and hardware components are required for semi-active control, which makes the system complex and costly. In this paper, a variable-orifice damper (VOD) for smart base-isolation system is proposed. The VOD can adaptably adjust its damping according to the frequency of the ground motion without additional power or sensors. Theoretical analysis and sinusoidal excitation tests were carried out to investigate the behavior of VOD. A series of numerical simulations of a base‐isolated structure equipped with the proposed VOD and subjected to ground motions are also conducted. A semi-active control with ON-OFF strategy, and two passive controls (passive-on and passive-off) are conducted for comparison. The simulation results show that the VOD can result in an optimal control under ground motions with different frequency characteristics.
An initial magnet experiment using high-temperature superconducting STAR® wires
Authors: Wang Xiaorong , Bogdanof Timothy J , Ferracin Paolo , Ghiorso William B , Gourlay Stephen A , Higley Hugh C , Kadiyala Janakiram Kaushal , Kar Soumen , Lee Reginald , Luo Linqing , Maruszewski Maxwell A , Memmo Robert , Myers Cory S , Prestemon Soren O , Sandra Jithin Sai , Selvamanickam Venkat , Teyber Reed , Turqueti Marcos , Wu Yuxin 
Published: November 2022

Abstract
A dipole magnet generating 20 T and beyond will require high-temperature superconductors such as Bi2Sr2CaCu2O

8
−
x

and REBa2Cu3O

7
−
x

(RE = rare earth, rebco). Symmetric tape round (star®) wires based on rebco tapes are emerging as a potential conductor for such a magnet, demonstrating a whole-conductor current density of 580 A mm−2 at 20 T, 4.2 K, and at a bend radius of 15 mm. There are, however, few magnet developments using star® wires. Here we report a subscale canted

cos
θ

dipole magnet as an initial experiment for two purposes: to evaluate the conductor performance in a magnet configuration and to start developing the magnet technology, leveraging the small bend radius afforded by star® wires. The magnet was wound with two star® wires, electrically in parallel and without transposition. We tested the magnet at 77 and 4.2 K. The magnet reached a peak current of 8.9 kA, 78% of the short-sample prediction at 4.2 K, and a whole-conductor current density of 1500 A mm−2. The experiment demonstrated a minimum viable concept for dipole magnet applications using star® wires. The results also allowed us to identify further development needs for star® conductors and associated magnet technology to enable high-field rebco magnets.
Fabrication and characterization of NbN/(TaN/NbN)
N
stacked Josephson junctions
Authors: Zhang Lu , Tao Yuanhe , Zhong Yulong , Yan Kaixin , Zeng Junwen , Shi Weifeng , Wu Ling , Wang Huiwu , Chen Lei , Peng Wei , Wang Zhen 
Published: November 2022

Abstract
In this work, we present a detailed study of the electrical properties of stacked NbN/(TaN/NbN)
N
Josephson junctions. Cross-sectional scanning transmission electron microscopy analysis of the 5-stacked junction shows that the multilayer interface is very flat, each barrier has the same thickness, and the sidewalls of the junctions are nearly perpendicular to the substrate. Stacked junctions of different sizes and stacking numbers all have only one transition in their current–voltage curves. This indicates that the critical currents of the junctions in the stacked junctions are almost the same, showing the stability and repeatability of the multilayer fabrication and etching process. At 4.2 K, the 4-stacked junction shows excellent Josephson properties with characteristic voltage V
c of 3.54 mV, which is about four times the 0.88 mV of the single junction. The temperature dependence of critical current density J
c and V
c of the stacked junction with N = 1, 2, 4 were measured, all of which can be fitted with dirty-limit theory. Stacked junctions with larger V
c or more stacked layers can be achieved by optimizing electrode and barrier thickness, barrier resistivity, and thermal relaxation rate, etc.
Isolated ultra-bright attosecond pulses via non-collinear gating
Authors: Kennedy J P , Dromey B , Yeung M 
Published: November 2022

Abstract
When light with relativistic intensity is incident on a solid target, bright attosecond pulses of extreme ultraviolet and x-ray radiation can be generated in the reflected beam. Unfortunately, the use of multi-cycle laser pulses results in trains of these attosecond pulses. Here we investigate a non-collinear gating scheme applied to surface high-harmonic generation to allow for the extraction of a single intense attosecond pulse from this train. Using 3D and 2D particle in cell (PIC) simulations we demonstrate that it is possible to angularly isolate a single attosecond pulse from the main driving laser pulse using this interaction geometry with intensities I > 1020 W cm−2. This result opens the door to generating bright attosecond pulses from relativistic plasmas without the need to spectrally filter the driving laser pulse.
Observation of collectivity enhanced magnetoassociation of 6Li in the quantum degenerate regime
Authors: Naniyil Vineetha , Zhou Yijia , Simmonds Guy , Cooper Nathan , Li Weibin , Hackermüller Lucia 
Published: November 2022

Abstract
The association process of Feshbach molecules is well described by a Landau–Zener (LZ) transition above the Fermi temperature, such that two-body physics dominates the dynamics. However, using 6Li atoms and the associated Feshbach resonance at B
r = 834.1 G, we observe an enhancement of the atom–molecule coupling as the fermionic atoms reach degeneracy, demonstrating the importance of many-body coherence not captured by the conventional LZ model. In the experiment, we apply a linear association ramp ranging from adiabatic to non-equilibrium molecule association for various temperatures. We develop a theoretical model that explains the temperature dependence of the atom–molecule coupling. Furthermore, we characterize this dependence experimentally and extract the atom–molecule coupling coefficient as a function of temperature, finding qualitative agreement between our model and experimental results. In addition, we simulate the dynamics of molecular association during a nonlinear field ramp. We find that, in the non-equilibrium regime, molecular association efficiency can be enhanced by sweeping the magnetic field cubically with time. Accurate measurement of the atom–molecule coupling coefficient is important for both theoretical and experimental studies of molecular association and many-body collective dynamics.
Magneto-optical double zero-index media and their electromagnetic properties in the bulk
Authors: Feng Fanghu , Wang Neng , Wang Guo Ping 
Published: November 2022

Abstract
Double-zero-index media (DZIM) with zero permittivity and permeability are one important class in zero-refractive index photonics. Here, we extended the concept of DZIM and proposed a more general type, i.e., the magneto-optical DZIM (MODZIM), of which the permittivity and the determinant of the Hermitian permeability tensor are simultaneously zero. By formulating the Maxwell’s equations in the basis of complex-valued axes and using some mathematical principles, we studied the electromagnetic (EM) properties in the bulk of the MODZIM with different boundaries and impurities. Inside the MODZIM which is infinite along in the out-of-plane direction, it is shown that the scalar (out-of-plane) field is not uniform in general, in contrast to traditional DZIM where the scalar field is always uniform in the bulk. Nevertheless, for a normal incidence, the uniform scalar field inside the MODZIM can be achieved by optimizing the boundary conditions and doping some types of impurities, such as resonant round cylinders and arbitrary shaped media with a zero permeability. As long as the scalar field is uniform, the propagation of the EM wave inside the MODZIM can be analyzed with closed-form expressions. Our work will extend the study of zero-refractive-index photonics and provide deeper understanding of wave dynamics in the bulk of MODZIM.
Theoretical and experimental investigation of the metal–insulator transition in disordered anti-dot graphene
Authors: Zhang Ting , Zhang Haijing , Pan Jie , Sheng Ping 
Published: November 2022

Abstract
We study the transport behavior of anti-dot graphene both theoretically and experimentally, where the term ‘anti-dot’ denotes the graphene layer to be nanostructured with a periodic array of holes. It has been shown that the electronic band structure of the anti-dot graphene can be described by a 4 by 4 effective Hamiltonian (Pan J et al 2017 Phys. Rev. X. 7 031043) with a gap around the Dirac point, attendant with a 0 to π variation of the Berry phase as a function of energy, measured from the band edge. Based on the diagrammatic method analysis and experiments, we identify an energy-dependent metal-to-insulator transition (MIT) in this two-dimensional (2D) system at a critical Fermi energy ɛ
c, characterized by the divergence of the localization length in the Anderson localization phase to a de-localized metallic phase with diffusive transport. By measuring the conductance of square samples with varying dimension and at different Fermi energies, experiments were carried out to verify the theory predictions. While both theory and experiment indicate the existence of a 2D MIT with similar localization length divergence exponent, the values of the critical energy ɛ
c and that of the localization length do not show quantitative agreement. Given the robust agreement in the appearance of a 2D MIT, we attribute the lack of quantitative agreement to the shortcomings in the theoretical model. The difficulties in addressing such shortcomings are discussed.
Low-frequency underwater sound absorption metamaterial
Authors: Wang Tian , Wang Gui-Bo , Zhang Ruo-Jun , Ke Man-Zhu 
Published: November 2022

Abstract
Air bubbles in liquid are known for exhibiting low-frequency resonance and can be considered as passive scatterers. In this paper, we design an acoustic metamaterial consisting of an air bubble in a water-filled metal shell with an opening to develop low frequency underwater sound absorber. Numerical simulation is carried out by using finite element method, and the results show that the metamaterial sound absorber achieves quasi-prefect sound absorption coefficient (up to 0.96) at the frequency of 900 Hz based on the coupling resonance between the elastic bubble and the metal shell matrix. By replacing the single unit with a 3-unit composite structure, the acoustic metamaterial absorber can extend the working frequency from 830 Hz to1330 Hz, with still high absorption coefficient above 0.8. Our design acoustic metamaterial has potential applications in underwater noise control.
Coexistence of multiscroll chaotic attractors in two coupled inertial Hopfield neurons: numerical simulations and experiment
Authors: Sriram Sridevi , Danao Adile Adoum , Fonzin Theophile Fozin , Rajagopal Karthikeyan , Kengne Jacques 
Published: November 2022

Abstract
In this contribution, we consider the dynamics of a pair of coupled inertial neurons with hyperbolic tangent activation function. The two inertial neurons are coupled by adding to each one’s amplitude a perturbation proportional to the other one. The model is governed by a fourth-order autonomous system with hyperbolic tangent nonlinearities. The analysis of the coupled system yields nine equilibrium points some of which experience Hopf type bifurcation. When adjusting the coupling coefficients, striking nonlinear patterns are disclosed such as the coexistence of numerous bifurcation branches, merging crisis, multiple Hopf bifurcations, coexisting self-excited motions (e.g. two coexisting double-scroll chaos, four coexisting period-n cycles, four coexisting single-scroll chaos), and four-scroll chaotic attractors. These latter features are diagnosed with the help of classic numerical tools (e.g. 1D and 2D maximum Lyapunov exponent diagrams, 1D bifurcation diagrams of local peaks of variables, frequency spectrum plots, phase space trajectory plots, and attraction basins). The analogue electronic circuit design of the coupled inertial neurons system is carried out and simulated in PSpice to verify diverse types of features reported during the theoretical study. One of main achievements of the present article is that the coupling of inertial neurons can be regarded as an alternative scheme to obtain multiscroll chaotic signals.
Solitons, single- and synchronous dual-wavelength noise-like pulses and hybrid regimes from a thulium-doped fiber laser
Authors: Ibarra-Garrido A , Durán-Sánchez M , Pottiez O , Bello-Jiménez M , Alaniz-Baylón J , Rodríguez-Morales L A , Armas-Rivera I , Ibarra-Escamilla B 
Published: November 2022

Abstract
In a passively mode-locked thulium-doped fiber laser within the anomalous dispersion regime, we experimentally demonstrate conventional soliton (CS), hybrid (noise-like pulse (NLP) and solitons), as well as switchable single-wavelength and synchronous dual-wavelength NLP regimes. By properly adjusting the PCs, we can switch between CS to hybrid and single- or dual-wavelength NLP regimes. With sufficient pumping power and through manual polarization adjustments, self-starting mode locking at 1996 nm can be observed. At the pump power of 2.5 W, stable mode locking with an output power of 86 mW is obtained. When generating the CS state, Kelly sidebands due to the spectral interference of dispersive waves are observed. Keeping the pump power at 2.5 W but with a modification of the polarization adjustment we can switch to five different regimes involving NLPs with squared envelope. The noise-like nature of the squared pulses was confirmed in each case through an autocorrelation measurement. By additional adjusting of the PCs, single- and synchronous dual-wavelength squared NLPs can be generated, at either one of two wavelengths in the former case, and at both simultaneously in the latter. The pulse trains from the single-wavelength operations display a small difference in their repetition frequencies inherently determined by intracavity dispersion, whereas in dual-wavelength operation the pulse train displays a single repetition rate whose value is intermediate between the single-wavelength frequencies. The obtained results are valuable to deepen our understanding on the formation of CS and dual-wavelength pulses with noise-like squared profiles in fiber lasers.
Stable high-efficiency continuous-wave diamond Raman laser at 1178 nm
Authors: Sun Yuxiang , Li Muye , Kitzler Ondrej , Mildren Richard Paul , Bai Zhenxu , Zhang Hongchao , Lu Jian , Feng Yan , Yang Xuezong 
Published: November 2022

Abstract
We demonstrate a high-efficiency continuous-wave (CW) diamond Raman laser operating at 1178 nm with enhanced stability by using a V-cavity design. A maximum Stokes power of 39 W with a conversion efficiency of 45% was achieved using a linearly-polarized 1018 nm Yb-doped fiber pump laser. The Stokes CW power stability showed superior stability over a linear cavity when characterized over periods up to 15 min. The Stokes output was found to switch between linear, elliptical, and random polarization with varying pump polarization. The results represent a major step towards stable, efficient and high-power CW lasers at 1178 nm and at wavelengths outside the main Yb, and Nd emission bands.
Magnon-mediated multi-channel high-order sideband generation in cavity magnonics
Authors: Fu Yan , Yang Lin , Cao Man , Kong Cui 
Published: November 2022

Abstract
We propose a scheme to describe magnon-mediated multi-channel high-order sideband generation in a cross cavity magnonic system. The high-order sideband generation is composed of equally spaced discrete output frequency components, which is essential tools for light communication, precision metrology, timing and spectroscopy. Beyond the generally linearized description by using the perturbative method, we deal with the Heisenberg–Langevin equations in the non-perturbative regime to obtain the output spectrum of high-order sidebands. Unlike conventional methods of using power that requires externally adjustable incident beams, here we demonstrate magnon-mediated high-order sideband generation in a cavity magnonic device by utilizing its intrinsically good tunability. Furthermore, until now most of the work in cavity magnonics is mainly restricted to the frequency/time domain, while we realize the modulation of sideband effects by the manipulation of cavity-magnon polaritons in real space, that is the external magnetic field with a tunable angle. By tuning the angle, we can obtain multi-channel high-order sideband generation, which may offer the potential for selectively transferring coherent information processing technologies.
Spectral radiance standard transfer for an integrating sphere as a radiation source in the ultraviolet band
Authors: Li Jia-wei , Chen Hong-yao , Zhang Li-ming , Huang Wen-xin , Yang Bao-yun 
Published: November 2022

Abstract
We developed a new source, having uniform spectral radiance, for a large-aperture UV integrating sphere with pressed polytetrafluoroethylene coating. Since lamp panel systems have high uncertainty due to a low signal-to-noise ratio at 250 nm, to transfer the spectral radiance scale from 250 nm to 350 nm to the source, we developed and calibrated a filter radiometer based on a solar blind phototube. The spectral radiance was obtained via a model of the source and a recursive estimation of the model parameters. A standard FEL lamp validated the usage of the filter radiometer. Finally, the filter radiometer to calibrate the new source. The results show that the radiance of the source at 250 nm is five times the top-of-the-atmosphere spectral irradiance, and the expanded uncertainty is 4.7%.
Statistical properties of sites visited by independent random walks
Authors: Ben-Naim E , Krapivsky P L 
Published: November 2022

Abstract
The set of visited sites and the number of visited sites are two basic properties of the random walk trajectory. We consider two independent random walks on hyper-cubic lattices and study ordering probabilities associated with these characteristics. The first is the probability that during the time interval (0, t), the number of sites visited by a walker never exceeds that of another walker. The second is the probability that the sites visited by a walker remain a subset of the sites visited by another walker. Using numerical simulations, we investigate the leading asymptotic behaviors of the ordering probabilities in spatial dimensions d = 1, 2, 3, 4. We also study the time evolution of the number of ties between the number of visited sites. We show analytically that the average number of ties increases as a
1 ln t with a
1 = 0.970 508 in one dimension and as (ln t)2 in two dimensions.
Extreme value statistics of positive recurrent centrally biased random walks
Authors: Artuso Roberto , Onofri Manuele , Pozzoli Gaia , Radice Mattia 
Published: November 2022

Abstract
We consider the extreme value statistics of centrally-biased random walks with asymptotically-zero drift in the ergodic regime. We fully characterize the asymptotic distribution of the maximum for this class of Markov chains lacking translational invariance, with a particular emphasis on the relation between the time scaling of the expected value of the maximum and the stationary distribution of the process.