bluuebunny/crossref_metadata_2025 huggingface dataset:
Local structures of phosphorus atoms implanted in crystalline diamond
Authors: Hoshino Yasushi , Seki Yuhei , Mitsuhara Kei
Published: October 2022

Effective impurity doping into diamond by an ion implantation technique has been one of the crucial issues for realizing diamond-based high-power electronic devices. Especially for n-type impurity doping, the electrical activation has not been accomplished yet in a practically available level. In this study, local structures and depth profiles of implanted phosphorus atoms were studied by x-ray absorption spectroscopy, secondary ion mass spectroscopy, and first-principles calculations. P ion implantations were performed at two extreme substrate temperatures of room temperature and 900°C at multiple incident energies from 10 to 150 keV for flat doping and a single energy of 200 keV for δ-doping followed by activation annealing at 1300°C. The x-ray absorption spectra and the theoretical calculation showed that most of the implanted phosphorus atoms implanted with a flat doping concentration are existent in the substitutional site; however, they seem to bond with hydroxyl or vacancy complexes, probably resulting in electrical inactivation. Indeed, secondary ion mass analysis showed that a large number of O and H atoms are distributed in the P-doped layer, probably diffused from the surface through a damaged network. On the other hand, impurity diffusion was not observed in the P δ-doped sample followed by high-temperature annealing with a cap layer. It is clearly suggested that a damaged layer by ion irradiation near the surface acts as diffusion channels and trap sites of various impurities. High-temperature annealing with a cap layer is also quite effective in suppressing the formation of the defective layer that becomes a diffusion path of O and H.
Mixed-mode chimera states in pendula networks
Authors: Ebrahimzadeh P. , Schiek M. , Maistrenko Y.
Published: October 2022

We report the emergence of peculiar chimera states in networks of identical pendula with global phase-lagged coupling. The states reported include both rotating and quiescent modes, i.e., with non-zero and zero average frequencies. This kind of mixed-mode chimeras may be interpreted as images of bump states known in neuroscience in the context of modeling the working memory. We illustrate this striking phenomenon for a network of N=100 coupled pendula, followed by a detailed description of the minimal non-trivial case of N=3. Parameter regions for five characteristic types of the system behavior are identified, which consist of two mixed-mode chimeras with one and two rotating pendula, classical weak chimera with all three pendula rotating, synchronous rotation, and quiescent state. The network dynamics is multistable: up to four of the states can coexist in the system phase state as demonstrated through the basins of attraction. The analysis suggests that the robust mixed-mode chimera states can generically describe the complex dynamics of diverse pendula-like systems widespread in nature.
A novel method to predict current–voltage characteristics of positive corona discharges based on a perturbation technique. II. Global analysis and applications to electrohydrodynamic thrusters
Authors: Shibata Hisaichi , Takaki Ryoji
Published: October 2022

Electrohydrodynamic (EHD) thrusters can silently propel small unmanned aerial vehicles without moving parts using corona discharges. Computational fluid dynamics would be a powerful tool to model the EHD thrusters and then optimize them. The drift-diffusion-Poisson equations govern corona discharges; hence, the equations can predict the current–voltage characteristics curves of EHD thrusters. However, the equations are too stiff to analyze EHD thrusters in the time domain. Here, we propose a perturbation technique to efficiently solve the stiff drift-diffusion-Poisson system in global (i.e., full two-dimensional or three-dimensional) and nonlinear (i.e., applied voltages higher than the corona inception voltage) regimes. Furthermore, we validated the method with the experimental results of a previous study.
Development of a repetitive plasma source for simulation of mitigated edge localized mode transient heat load
Authors: Liu Shuai , Xu Tao , Shi Yuhao , Zhan Wei , Liu Chengying , Lu Zhijian , Yang Lanjun
Published: October 2022

A repetitive plasma source for simulation of mitigated edge localized mode transient heat load is developed. The repetitive plasma source consists of a repetitive pulsed power supply and a pulsed plasma accelerator. The pulsed plasma accelerator is composed of a coaxial cathode, an anode, and an insulator. The inner electrode is the cathode with a diameter of 5 mm, and the outer electrode is the anode with a diameter of 15 mm. An angular magnetic field is generated by the discharge current and acts with the radial current to generate Lorentz force, which drives the plasma ejecting to the outlet. The repetitive pulsed power supply can be divided into three parts, the primary charge circuit, the resonant charge circuit, and the discharge circuit. The time interval between resonant charge and discharge is 4 ms. The repetitive discharge components include ten modules running in parallel. There are four working modes for discharge components, depending on the number of simultaneously discharged modules. For Mode A, the maximum repetitive frequency is 50 Hz, and the transient heat load is 0.06 MJ/m2 when the discharge current is 10.5 kA. For Mode D, the maximum repetitive frequency is 5 Hz, and the transient heat load is 0.45 MJ/m2 when the discharge current is 66 kA. This is of great significance for the study of the interaction between plasma and plasma-facing materials in tokamak.
Design and numerical investigation of cadmium telluride (CdTe) and iron silicide (FeSi2) based double absorber solar cells to enhance power conversion efficiency
Authors: Rahman Md. Ferdous , Habib M. J. A. , Ali Md. Hasan , Rubel M. H. K. , Islam Md. Rounakul , Md. Ismail Abu Bakar , Hossain M. Khalid
Published: October 2022

Inorganic CdTe and FeSi2-based solar cells have recently drawn a lot of attention because they offer superior thermal stability and good optoelectronic properties compared to conventional solar cells. In this work, a unique alternative technique is presented by using FeSi2 as a secondary absorber layer and In2S3 as the window layer for improving photovoltaic performance parameters. Simulating on SCAPS-1D, the proposed double-absorber (Cu/FTO/In2S3/CdTe/FeSi2/Ni) structure is thoroughly examined and analyzed. The window layer thickness, absorber layer thickness, acceptor density (NA), donor density (ND), defect density (Nt), series resistance (RS), and shunt resistance (Rsh) were simulated in detail for optimization of the above configuration to improve the PV performance. According to this study, 0.5 µm is the optimized thickness for both the CdTe and FeSi2 absorber layers in order to maximize the efficiency (η). Here, the value of the optimum window layer thickness is 50 nm. For using CdTe as a single absorber, η is achieved by 13.26%. However, for using CdTe and FeSi2 as a dual absorber, η is enhanced and the obtaining value is 27.35%. The other parameters are also improved and the resultant value for the fill factor is 83.68%, the open-circuit voltage (Voc) is 0.6566 V, and the short circuit current density (Jsc) is 49.78 mA/cm2. Furthermore, the proposed model performs well at 300 K operating temperature. The addition of the FeSi2 layer to the cell structure has resulted in a significant quantum efficiency enhancement because of the rise in solar spectrum absorption at longer wavelengths (λ). The findings of this work offer a promising approach for producing high-performance and reasonably priced CdTe-based solar cells.
Atomic diffusion in liquid Al–Cu melt under static magnetic fields
Authors: Zhou Bangfei , Lin Wenhao , Liu Ying , Cai Hao , Zheng Tianxiang , Liu Chunmei , Zhong Yunbo
Published: October 2022

Atomic diffusion is a natural phenomenon in liquid melt. Avoiding the melt convection is the most challenging when accuracy in measuring the diffusion coefficient of atoms is desired. The diffusion in liquid Al–Cu melts is studied under various static magnetic fields (SMFs). Thermoelectric magnetic convection is induced during the diffusion in the conductive crucible. It is suppressed by increasing the magnetic flux density or eliminated by using an insulated crucible. The interdiffusion coefficient can be accurately measured in the SMF greater than 3 T. The present work provides a new view to study the solidification of alloys under the SMF.
Effect of relative locations between internal transport barrier and
q
min on HL-2M’s kink-ballooning stability
Authors: Wang Yuanzhen , Xu Xinliang , Sun Aiping , Li Zhengji , Wang Zhuo , Liu Yue , Sun Ziyuan
Published: October 2022

The significance of relative locations between the internal transport barrier (ITB) and the minimum value of safety factor (qmin) is proved by the magnetohydrodynamic (MHD) stability of ITB plasma, in shaped tokamak devices. In this work, equilibria of HL-2M tokamak with different locations of ITB and qmin are generated using the TOQ code, and the kink-ballooning stabilities of the equilibria with respect to 1 ≤ n ≤ 20 (n is the toroidal mode number) are simulated with the BOUT++ code. The results show that the MHD instability is suppressed magnificently, when the location of ITB is close to the core, while qmin is to the edge. The instability of the equilibrium is also stabilized when ITB is in the region with negative magnetic shear. As ITB moves toward the core or qmin moves toward the edge, the amplitude of negative magnetic shear increases, and the ITB gets closer to the negative magnetic shear, which benefits the MHD stability. Meanwhile, when qmin moves toward the edge, the elongation of the magnetic surface in the ITB region increases, and the area of the magnetic surface on the strong field side expands, which optimizes the magnetic surface distribution and improves the MHD stability.
hBN-based enhancement and regulation of radiative heat transfer between two monolayer graphene sheets
Authors: Song Jinlin , Chen Lei , Jin Lin , Yao Lei , Caglayan Humeyra , Hu Run
Published: October 2022

Near-field radiative heat transfer (NFRHT) in many-body systems has opened pathways for enabling novel thermal-radiation applications. In this Letter, we investigate hBN-based enhancement and regulation of NFRHT between two monolayer graphene sheets. On the one hand, we predict that adding an intermediate hBN plate can greatly compensate the exponential damping of evanescent waves due to its hyperbolic modes, thus leading to 1.5 times enhancement of the NFRHT without introducing additional thermal source compared to the graphene-graphene system. On the other hand, we find that adjusting the shift frequency of hBN can greatly change the coupling of its hyperbolic modes and graphene surface plasmon polaritons, thus enabling the remarkable thermal regulation with a ratio of 3.5. We hope that our work may facilitate nanoscale thermal management in many-body systems and benefit the comprehension of hBN-based photon tunneling.
Quasi-periodic micro-lens array via laser-assisted wet etching
Authors: Baek Gi Hyeon , Hwang Eui Sun , Cheong Byoung-Ho
Published: October 2022

A close-packed micro-lens array (MLA) is widely used not only in novel optical systems but also in various engineering fields, such as semiconductors and display devices. In this paper, we present a simple and efficient method for fabricating MLAs on a glass substrate via laser ablation with a single femtosecond laser pulse and chemical wet etching in a hydrofluoric acid solution. The shapes of concave micro-lenses were optimized for laser pulse energy and etching time, and ∼70 000 micro-lenses with 15 µm diameter were formed. The shape of the micro-lens varies significantly with respect to the etching time in accordance with an initial ablated area (or laser energy), which is a key feature in fabricating micro-lenses of several tens of μm. Using the glass MLA as a mold, a polydimethylsiloxane convex-plano lens array was replicated, and the performance of the optical imaging and beam integrator was then examined.
Genetic algorithms for the design of planar THz antenna
Authors: Fenlon Vanessa , Cooke Michael , Mayock Jim , Gallant Andrew , Balocco Claudio
Published: October 2022

This paper proposes a genetic algorithm for the design of passive components operating at THz frequencies and its experimental validation using an exemplar patch antenna. The patch antenna is based on an SU8 substrate, with a binary array describing the placement of metal “bits” replacing the conventional patch. These “bits” are constrained at 25 × 25 μm2, ensuring ease of fabrication. Optimal configurations of this array are determined using a finite-difference time-domain solver coupled to the genetic algorithm, which simulates and optimizes for maximum power collection in the frequency range of 0.10–5.0 THz. The aim was to produce an evolved patch antenna design with double the power collection efficiency across the majority of the frequency range compared to a reference, plain patch antenna of the same size. This was successful with a 5.3 dB mean improvement in simulated power collection compared to a plain reference patch. A vector network analyzer in conjunction with 0.80–1.0 THz frequency extenders was used to validate the simulation results. The antennas were arranged in pairs with variable feed length to determine the feedline attenuation and validate the simulated antenna directionality.
Auto-encoder-assisted analysis of amplitude and wavelength modulation of near-wall turbulence by outer large-scale structures in channel flow at friction Reynolds number of 5200
Authors: Agostini L. , Leschziner M.
Published: October 2022

This paper reports a novel methodology that allows the intensity of, and the underlying mechanism for, the amplitude and length-scale modulation (amplification or attenuation) of turbulent stresses in the inner layer of a channel flow at Reτ≈5200 to be clarified. A unique aspect of the present framework is the use of an auto-encoder algorithm to separate full-volume extremely large direct numerical simulation (DNS) fields into large-scale and small-scale motions. This approach is adopted in preference to the empirical mode decomposition (EMD) previously used by the present authors at the lower Reynolds number, Reτ≈1000, because resource requirements posed by the EMD quickly become untenable due to the extremely large DNS dataset and the large solution box needed to capture the wide spectrum of scales at the present Reynolds number. A second original element is a formalism that derived the modulation, conditional on large-scale fluctuations, from continuous statistical quantities represented as multivariable-joint probability-density functions, thus obviating the need for any discrete representation or binning beyond that imposed by the discrete DNS solution. A third novel aspect is the use of the length-scale-wise derivative of the second-order structure function to quantify the modulation (increase or decrease) in the length scale, again conditional on large-scale structures. Apart from illuminating the modulation itself, the study examined the validity of the quasi-steady hypothesis that proposes that the near-wall turbulence is universal when scaled by the spatially and temporally varying large-scale wall shear stress rather than its time average.
Unmet expectations? The impact of the Coronavirus crisis on radical right populism in North-Western and Southern Europe
Authors: Crulli Mirko
Published: October 2022

This article investigates the state of health of the populist radical right in North-Western and Southern European democracies after the outbreak of the pandemic. The research question is whether the Coronavirus crisis represents an enemy or an ally of populist radical right (PRR) parties in these European regions. The thesis put forward is that a priori, based on the copious literature of political sociology and political science on populism, there are four interrelated compelling reasons to argue that PRR parties can benefit from the pandemic. However, I show how the polls and the national elections held during the pandemic suggest the opposite, namely that populist radical right forces have overall found in the Coronavirus crisis a little more an enemy than an ally. Finally, I suggest four remarks on why we are facing this unexpected outcome.
Frustrated Magnetic Interactions and Quenched Spin Fluctuations in CrAs
Authors: Qin Yayuan , Shen Yao , Hao Yiqing , Wo Hongliang , Shen Shoudong , Ewings Russell A. , Zhao Yang , Harriger Leland W. , Lynn Jeffrey W. , Zhao Jun
Published: October 2022

The discovery of pressure-induced superconductivity in helimagnets (CrAs, MnP) has attracted considerable interest in understanding the relationship between complex magnetism and unconventional superconductivity. However, the nature of the magnetism and magnetic interactions that drive the unusual double-helical magnetic order in these materials remains unclear. Here, we report neutron scattering measurements of magnetic excitations in CrAs single crystals at ambient pressure. Our experiments reveal well defined spin wave excitations up to about 150 meV with a pseudogap below 7 meV, which can be effectively described by the Heisenberg model with nearest neighbor exchange interactions. Most surprisingly, the spin excitations are largely quenched above the Néel temperature, in contrast to cuprates and iron pnictides where the spectral weight is mostly preserved in the paramagnetic state. Our results suggest that the helimagnetic order is driven by strongly frustrated exchange interactions, and that CrAs is at the verge of itinerant and correlation-induced localized states, which is therefore highly pressure-tunable and favorable for superconductivity.
Sub-band response of PZT photodetector controlled by back-gate voltage
Authors: Chen Anqi , Lv You , Su Longxing , Zhu Yuan
Published: October 2022

Sub-band energy levels induced photo-conduction mechanisms play a significant role in the extension of the response spectra within a photodetector. Herein, we reported a PbZr0.32Ti0.68O3 (PZT) based photodetector for sub-band photoresponse excited by a 450 nm blue laser. Sub-band induced by the defects acts as the intermediate state for the intra-band transition excited by the blue laser, in which the photon energy is smaller than the bandgap of the PZT thin film. Within both gate-controlled and blue laser driven operations, the source to drain current (I
sd) can be precisely modulated. The photocurrent and response speeds of the device are also studied under air and vacuum conditions, which shows negligible fluctuations under different atmospheres and excludes the negative influence from the defect-related surface states. The proposed device configuration provides a simple and cost-effective visible light driven photodetector, which may give rise to an interesting route towards optoelectronic devices based on ferroelectric material.
CeO2-NiO-rGO as a nano-electrocatalyst for methanol electro-oxidation
Authors: Askari Mohammad Bagher , Moghadam Mohammad Taghi Tourchi , Azizi Sadegh , Hashemi Seyed Rouhollah Samareh , Shojaeifar Mohsen , Di Bartolomeo Antonio
Published: October 2022

This study provides the methanol oxidation capability of two nanocatalysts, CeO2-NiO (CN) and CeO2-NiO-rGO (CNR), synthesized by a cost-effective hydrothermal method. The synergistic effect of compositing CeO2-NiO with reduced graphene oxide was evaluated. These synergic effect makes a good electrochemical active surface area and suitable electrical conductivity for catalyst. In addition, rGO with good electrical conductivity revealed considerable improvement in the methanol oxidation reaction performance of the catalyst. The cyclic stability measurements of CeO2-NiO-rGO showed a high retention ability of 96% in 500 consecutive cyclic voltammetry cycles, while the stability of CeO2-NiO in the same number of cycles is about 93%. The complementary methanol oxidation process results indicated an oxidation current density up to 49.5 and 68.5 mA cm−2 for CN and CNR at a scan rate of 20 mV s−1, respectively. The proposed catalyst can be considered as an attractive, stable, and inexpensive candidate in the field of methanol oxidation to use in methanol fuel cells.
Polarization due to emergent polarity in elemental semiconductor thinfilms under bending
Authors: Tang J-K , Wang Y-X , Chang K , Zhang D-B
Published: October 2022

Polarization via strain engineering provides a facial way to functionalize materials. We investigate the origin of electronic polarization in the bent elemental semiconductor thinfilms by combining analytical modeling with quantum mechanical simulation. A bond orbital model reveals a polarity of covalent bonds induced by strain gradient such that polarization along the strain gradient dimension can be induced, giving rise to the flexoelectric effect. At strain gradient

1

/

R
=
0.01

 nm−1, the net charge differences between the two sides are

5
×

10

−
4

e

,

2.5
×

10

−
3

e

and

7.2
×

10

−
3

e

for C, Si and Ge films respectively. On the other hand, due to the emergent bond polarity, the polarization can be effectively tuned by normal strain applied to the bent film, mimicking the piezoelectric effect. Simulations using the generalized Bloch theorem strongly support this revelation. Findings have important implications for delineating the formation of polarization and related phenomena in semiconductors.
TMSST-CK fault feature extraction method for flexible thin-wall bearing based on the Gini index principle
Authors: Yu Yanjiang , Zhao Xuezhi , Yu Chaofeng
Published: October 2022

A flexible thin-wall bearing (FTB) is forced to deform with the elastic deformation of the flexspline in motion, resulting in a completely different fault characteristic frequency (FCF) from ordinary rolling bearings. However, current extraction methods treat FTBs as ordinary ones and they are analyzed based on the spectrum, without considering the time-varying nature of the FCF in an FTB. In an effort to address this concern, this paper proposes a Gini index-based time-reassigned multisynchrosqueezing transform, where the window size is determined by the period impulses feature in the noise-removed signal. In addition, a frequency point selection method that contains fault characteristics of the FTB is proposed by calculating the maximum correlated kurtosis in the time–frequency (TF) plane. Furthermore, the instantaneous frequency is extracted by calculating the time interval between two consecutive impulses. The extracted fault frequency agrees well with the experimental result and outperforms other TF analysis techniques in demonstrating its time-varying nature.
Dislocation nucleation mechanisms during nanoindentation of concentrated FeNiCr alloys: unveiling the effects of Cr through molecular simulations
Authors: Dominguez-Gutierrez F J , Ustrzycka A , Xu Q Q , Alvarez-Donado R , Papanikolaou S , Alava M J
Published: October 2022

Fe-based alloys with high chromium and nickel concentrations are very attractive for efficient energy production in extreme operating conditions. We perform molecular dynamics (MD) simulations of nanoindentation on fcc FeNiCr multicomponent materials. Equiatomic FeNi, Fe55Ni19Cr26, and Fe74Ni8Cr18 are tested by using established interatomic potentials and similar conditions, for the elucidation of key dislocation nucleation mechanisms and interactions. Generally, we find that the presence of Cr in these alloys reduces the mobility of prismatic dislocation loops, and increases their area, regardless of crystallographic orientation. Dislocation nucleation and evolution is tracked during mechanical testing as a function of nanoindentation strain and Kocks–Mecking continuum modeling displays good agreement with MD findings. Furthermore, the analysis of geometrically necessary dislocations (GNDs) is consistent with the Ma–Clarke’s model at depths lower than 1.5 nm. The presence of Cr leads to a decrease of the GND density with respect to Cr-less FeNi samples, thus we find that Cr is critically responsible of increasing these alloys’ hardness. Post-indentation impression maps indicate that Ni–Fe–Cr compositions display strain localization and hardening due to high Cr concentration.
Object kinetic Monte Carlo modelling of irradiation microstructures with elastic interactions
Authors: Jourdan T
Published: October 2022

Elastic interactions between point defects and sinks, such as dislocations and cavities, affect the diffusion of point defects and are responsible for some of the features observed in microstructures under irradiation. It is therefore necessary to include elastic interactions in kinetic simulations for a quantitative prediction of material properties. In this work a method is presented to accurately and efficiently evaluate the strain field in object kinetic Monte Carlo simulations. It can handle any strain field which is biharmonic, such as the one generated by a dislocation segment or a cavity in isotropic elasticity. A speed-up of several orders of magnitude is obtained compared to the direct summation over strain sources, so that simulations over experimental time scales can be performed within reasonable computation times. The case of a thin foil containing a high density of loops under irradiation is investigated. Loop growth rates are found to depend on the loop radius, as shown experimentally, but more complex effects due to the surrounding microstructure are also highlighted.
Synthesis of graphene nanomesh with symmetrical fractal patterns via hydrogen-free chemical vapor deposition
Authors: Li Fang , Li You , Zhao Yibin , Liu Mingyan , Kan Erjun , Li Qiongyu , Wan Yi
Published: October 2022

Graphene nanomesh (GNM), an emerging graphene nanostructure with a tunable bandgap, has gained tremendous interests owing to its great potentials in the fields of high-performance field-effect transistors, electrochemical sensors, new generation of spintronics and energy converters. In previous works, GNM has been successfully obtained on copper foil surface by employing hydrogen as an etching agent. A more facile, and low-cost strategy for the preparation of GNM is required. Here, we demonstrated a direct and feasible means for synthesizing large-area GNM with symmetrical fractal patterns via a hydrogen-free chemical vapor deposition method. The influences of the growth time and the gas source flow on the morphology of GNM patterns were systematically investigated. Then, we exhibited the key reaction details and proposed a growth mechanism of the GNM synthesis during the hydrogen-free chemical vapor deposition process. This work provides a valuable guidance for quality control in GNM mass production.
Cavity ringdown studies of the E–H transition in an inductively coupled oxygen plasma: comparison of spectroscopic measurements and modelling
Authors: Rogers Samuel D A , Bond Amelia , Rhodes Benjamin J , Peverall Robert , Hancock Gus , Ritchie Grant A D
Published: October 2022

The absolute number density of ground state oxygen atoms, O(3P), present in a 100 mTorr oxygen plasma has been determined as a function of operating power using cavity ringdown spectroscopy (CRDS). The dissociation fraction increases by an order of magnitude from ∼0.8% at 50 W to 8% at 250 W and reflects a similar increase in the electron density over this power range. Emission spectra show that the E–H switchover is accompanied by increased rotational heating of O2 and this behaviour is also observed in the translational temperatures determined by fitting the Doppler limited O(3P) CRDS data. The measurements are contextualised via a volume averaged kinetic model that uses the measured absolute densities of O(3P) and O2(a
1Δg, v = 0) as a function of power as its benchmarks. Despite the inherent spatial inhomogeneity of the plasma, the volume averaged model, which uses a minimal set of reactions, is able to both reproduce previous measurements on the absolute density of O− and to infer physically reasonable values for both the electron temperature and number density as the E–H switch over is traversed. Time-resolved emission measurements return a value of 0.2 for the wall loss coefficient for O2(b
1Σg
+); as a consequence, the number density of O2(b
1Σg
+) is (at least) one order of magnitude less than O2(a
1Δg).
Effects of the ground-electrode temperature on the plasma physicochemical processes and biological inactivation functions involved in surface dielectric barrier discharge
Authors: Xu Han , Zhu Fan , Liu Yan , Quan Lei , Li Bo , Zhang Hao , Shao Mingxu , Xie Kai
Published: October 2022

In this work, a surface dielectric barrier discharge (SDBD) device coupled with power electronics technology was designed for precise control of the ground-electrode temperature to investigate the dynamic behavior of the physicochemical processes and biological inactivation functions involved in SDBD plasma. It was found that an increase of the electrode temperature from 30 to 210 °C reduced the breakdown voltage and increased the current pulse amplitude because the reduced electric field strength and average electron density of the SDBD plasma were consistently enhanced. The change in the plasma-chemistry mode (O3-dominant to NO
x
-dominant) was more sensitive to the ground-electrode temperature than that of the power density and gas temperature. O3 in the gas and liquid phases could not be detected at electrode temperatures above 90 °C, and the NO
x
mode almost immediately occurred after the plasma was turned on for ground-electrode temperatures of ⩾180 °C. The increase in the electrode temperature increased the acidity of the plasma-activated water and, more importantly, short-lived reactive species OH and NO were detected at electrode temperatures ⩾120 °C in the case of aqueous solutions treated directly with SDBD plasma. The biological inactivation function of the SDBD plasma, i.e. for bacterial suspensions and tumor cell cultures, was improved by about three orders of magnitude and 40% at the optimal electrode temperatures of 180 °C and 120 °C, respectively. This is an important breakthrough for development of SDBD-based biomedical devices for specific purposes on a commercial level by regulating the plasma chemistry through the ground-electrode temperature, overcoming the limitations of chamber heating and compressed air supply.
High performance piezoelectric vibration energy harvesting by electrical resonant frequency tuning
Authors: Gibus David , Morel Adrien , Gasnier Pierre , Ameye Adrien , Badel Adrien
Published: October 2022

Extending the frequency bandwidth (BW) of vibration energy harvesters (VEH) that power wireless sensor nodes is of scientific and industrial interest. In this aim, electrical methods to tune the resonant frequency of piezoelectric harvesters with strong electromechanical coupling coefficients have been developed. In this work, we provide guidelines for designing such strongly coupled VEH and present a broadband harvester with high normalized power density (NPD). Through an analytical model, we explain how the coupling coefficient

k
2

and the quality factor

Q
m

of a cantilever can be jointly maximized, thereby maximizing the figure of merit

k
e
2

Q
m

. The proposed cantilever prototype made of PZN-5.5PT and aluminum offers one of the best coupling coefficients among the state-of-the-art (k
2= 49.8%) and a high quality factor (Qm
= 140). Associated to an appropriate tunable electrical interface (short-circuit synchronous electric charge extraction (SECE) in our case), the prototype exhibits a NPD of 12.0 mW g−2 cm−3 and a frequency BW of 36.0% (56.5 Hz around 157 Hz) at 0.34 m s−2 with a tunable electrical interface: the short-circuit SECE. This represents the highest product NPW × BW from state of the art.
Design and analysis of passive variable stiffness device based on shear stiffening gel
Authors: Wenbin Chen , Xiang Fang , Jingming Che , Caihua Xiong
Published: October 2022

Shear thickening materials are utilized as the core of variable stiffness devices in various engineering applications in recent years. However, due to the used materials being liquid, most of these devices are suffered from the problem of liquid leakage and coagulation. To address this issue, this paper proposes a design method of a passive variable stiffness device based on shear stiffening gel (SSG), which integrates the core SSG and spring into a compact structure to obtain well stability. The used SSG can affect the force transfer within the device, thereby influencing the system’s stiffness dynamically over the external impact load. Due to the core SSG being good shear stiffening properties, the device is highly sensitive to frequency and shows variable stiffness characteristics. When the frequency of external load increased from 0.1 Hz to 5 Hz, the equivalent stiffness of the device could be increased by 105.74%. An equivalent nonlinear model is used to represent the overall stiffness of the device as a function of the frequency and displacement amplitude of the load. The output of the equivalent nonlinear model agrees well with the experimental data. The cross-validation also proves the accuracy of the model fitting, which provides a quantitative description of the dynamic performance of the variable stiffness device. By combining different types of SSGs and springs with different stiffness, the design principle of the variable stiffness device proposed in this paper can be utilized in various impact-loading applications, such as designing the exoskeletal load carriage supporting mechanism and vehicle suspension systems. The work of this paper has guiding significance for the design of adaptive variable stiffness devices.
Quantum interferometric two-photon excitation spectroscopy
Authors: Chen Yuanyuan , León-Montiel Roberto de J , Chen Lixiang
Published: October 2022

Two-photon excitation spectroscopy is a nonlinear technique that has gained rapidly in interest and significance for studying the complex energy-level structure and transition probabilities of materials. While the conventional spectroscopy based on tunable classical light has been long established, quantum light provides an alternative way towards excitation spectroscopy with potential advantages in temporal and spectral resolution, as well as reduced photon fluxes. By using a quantum Fourier transform that connects the sum-frequency intensity and N00N-state temporal interference, we present an approach for quantum interferometric two-photon excitation spectroscopy. Our proposed protocol overcomes the difficulties of engineering two-photon joint spectral intensities and fine-tuned absorption-frequency selection. These results may significantly facilitate the use of quantum interferometric spectroscopy for extracting the information about the electronic structure of the two-photon excited-state manifold of atoms or molecules without any requirement for precise and complicated scanning in the spectral domain. This may be particularly relevant for photon-sensitive biological and chemical samples.
The angular scale of homogeneity with SDSS-IV DR16 luminous red galaxies
Authors: Andrade Uendert , Gonçalves Rodrigo S. , Carvalho Gabriela C. , Bengaly Carlos A. P. , Carvalho Joel C. , Alcaniz Jailson
Published: October 2022

We report measurements of the angular scale of cosmic homogeneity (θH
) using the recently released luminous red galaxy sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV LRG DR16). It consists of a model-independent method, as we only use the celestial coordinates of these objects to carry out such an analysis. The observational data is divided into thin redshift bins, namely 0.67 < z < 0.68, 0.70 < z < 0.71, and 0.73 < z < 0.74, in order to avoid projection biases, and we estimate our uncertainties through a bootstrap method and a suite of mock catalogues. We find that the LRGs exhibit an angular scale of homogeneity consistent with the predictions of the standard cosmology within the redshift interval studied. Considering the bootstrap method, in which the measurements are obtained in a model-independent way, we found at 1σ level that θH

boot(0.675) = 7.57 ± 2.91 deg, θH

boot (0.705) = 7.49 ± 2.63 deg and θH

boot (0.735) = 8.88 ± 2.81 deg. Such results are in good agreement with the ones obtained using mock catalogues built under the assumption of the standard cosmological model.
Correlated states in alternating twisted bilayer-monolayer-monolayer graphene heterostructure
Authors: Niu Ruirui , Han Xiangyan , Qu Zhuangzhuang , Wang Zhiyu , Li Zhuoxian , Liu Qianling , Han Chunrui , Lu Jianming
Published: October 2022

Highly controlled electronic correlation in twisted graphene heterostructures has gained enormous research interests recently, encouraging exploration in a wide range of moiré superlattices beyond the celebrated twisted bilayer graphene. Here we characterize correlated states in an alternating twisted Bernal bilayer–monolayer–monolayer graphene of ∼ 1.74°, and find that both van Hove singularities and multiple correlated states are asymmetrically tuned by displacement fields. In particular, when one electron per moiré unit cell is occupied in the electron-side flat band, or the hole-side flat band (i.e., three holes per moiré unit cell), the correlated peaks are found to counterintuitively grow with heating and maximize around 20 K – a signature of Pomeranchuk effect. Our multilayer heterostructure opens more opportunities to engineer complicated systems for investigating correlated phenomena.
Lie symmetry analysis and invariant solutions for the (3+1)-dimensional Virasoro integrable model
Authors: Hu Hengchun , Li Yaqi
Published: October 2022

Lie symmetry analysis is applied to a (3+1)-dimensional Virasoro integrable model and the corresponding similarity reduction equations are obtained with the different infinitesimal generators. Invariant solutions with arbitrary functions for the (3+1)-dimensional Virasoro integrable model, including the interaction solution between a kink and a soliton, the lump-type solution and periodic solutions, have been studied analytically and graphically.
Modeling and Measuring Friction of the Leighton 10 m Telescope
Authors: Guo Yongwei , Woody David , Matinez Nicolas
Published: October 2022

Estimating and identifying friction are important aspects of simulating a mechanical drive system. Accurate friction modeling helps to improve a telescope's performance. However, the friction conditions inside are complex and hard to measure. We did simulations with mathematical transfer functions for the Leighton 10 m Telescope and employed a polyline model to identify sources of friction. We made a two-stage model for the Leighton 10 m Telescope. Based on measurements of the motor's currents and speeds, we constructed a curve containing the friction information of the transmission elements. We simulated the system using a step function input under many combinations of friction parameters. By comparing simulation results with the measured ones, we determined the various friction components. This model accurately reproduced the telescope performance including the nonlinearities.
Organic electro-optic polymer materials and organic-based hybrid electro-optic modulators
Authors: Wang Yan , Liu Tongtong , Liu Jiangyi , Li Chuanbo , Chen Zhuo , Bo Shuhui
Published: October 2022

High performance electro-optic modulator, as the key device of integrated ultra-wideband optical systems, have become the focus of research. Meanwhile, the organic-based hybrid electro-optic modulators, which make full use of the advantages of organic electro-optic (OEO) materials (e.g. high electro-optic coefficient, fast response speed, high bandwidth, easy processing/integration and low cost) have attracted considerable attention. In this paper, we introduce a series of high-performance OEO materials that exhibit good properties in electro-optic activity and thermal stability. In addition, the recent progress of organic-based hybrid electro-optic devices is reviewed, including photonic crystal-organic hybrid (PCOH), silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) modulators. A high-performance integrated optical platform based on OEO materials is a promising solution for growing high speeds and low power consumption in compact sizes.
Synthesis and electromagnetic transport of large-area 2D WTe2 thin film
Authors: Zhang Yumeng , Wang Zhejia , Feng Jiaheng , Ming Shuaiqiang , Qu Furong , Xia Yang , He Meng , Hu Zhimin , Wang Jing
Published: October 2022

Tungsten telluride thin films were successfully prepared on monocrystal sapphire substrates by using atomic layer deposition and chemical vapor deposition technology, and the effects of different tellurization temperatures on the properties of tungsten telluride films were investigated. The growth rate, crystal structure and composition of the film samples were characterized and analyzed by using scanning electron microscope, Raman spectroscopy and X-ray photoelectron spectroscopy. The results showed that tungsten telluride thin films with good crystal orientation in (001) were obtained at telluride temperature of 550 °C. When the telluride temperature reached 570 °C, the tungsten telluride began to decompose and unsaturated magnetoresistance was found.
Multilayer doped-GeSe OTS selector for improved endurance and threshold voltage stability
Authors: Zhang Shiqing , Song Bing , Jia Shujing , Cao Rongrong , Liu Sen , Xu Hui , Li Qingjiang
Published: October 2022

Selector devices are indispensable components of large-scale memristor array systems. The thereinto, ovonic threshold switching (OTS) selector is one of the most suitable candidates for selector devices, owing to its high selectivity and scalability. However, OTS selectors suffer from poor endurance and stability which are persistent tricky problems for application. Here, we report on a multilayer OTS selector based on simple GeSe and doped-GeSe. The experimental results show improving selector performed extraordinary endurance up to 1010 and the fluctuation of threshold voltage is 2.5%. The reason for the improvement may lie in more interface states which strengthen the interaction among individual layers. These developments pave the way towards tuning a new class of OTS materials engineering, ensuring improvement of electrical performance.
Towards a consensus on a continuous coordinated universal time
Authors: Levine Judah , Tavella Patrizia , Milton Martin
Published: October 2022

This paper explains the considerations that were important in 1972, when the current leap second procedure was adopted, to maintain a close connection between UTC, the international reference time scale, and UT1—a time scale based on the rotation of the Earth. Although some of these considerations are still relevant, the procedure for adding leap seconds creates difficulties in many modern applications that require a continuous and monotonic time scale. We present the advantages and disadvantages of the leap second procedure, and some of the problems foreseen if it is not reconsidered. We suggest the general outline of a way forward, which addresses the deficiencies in the current leap second system, and which will ensure that UTC remains an international standard that is useful and appropriate for all time and frequency applications. Further discussion and evaluation of the impact of any changes is required.
Modular pulse synthesizer for transcranial magnetic stimulation with fully adjustable pulse shape and sequence
Authors: Li Z , Zhang J , Peterchev A V , Goetz S M
Published: October 2022

The temporal shape of a pulse in transcranial magnetic stimulation (TMS) influences which neuron populations are activated preferentially as well as the strength and even direction of neuromodulation effects. Furthermore, various pulse shapes differ in their efficiency, coil heating, sensory perception, and clicking sound. However, the available TMS pulse shape repertoire is still very limited to a few biphasic, monophasic, and polyphasic pulses with sinusoidal or near-rectangular shapes. Monophasic pulses, though found to be more selective and stronger in neuromodulation, are generated inefficiently and therefore only available in simple low-frequency repetitive protocols. Despite a strong interest to exploit the temporal effects of TMS pulse shapes and pulse sequences, waveform control is relatively inflexible and only possible parametrically within certain limits. Previously proposed approaches for flexible pulse shape control, such as through power electronic inverters, have significant limitations: The semiconductor switches can fail under the immense electrical stress associated with free pulse shaping, and most conventional power inverter topologies are incapable of generating smooth electric fields or existing pulse shapes. Leveraging intensive preliminary work on modular power electronics, we present a modular pulse synthesizer (MPS) technology that can, for the first time, flexibly generate high-power TMS pulses (one-side peak ∼4000 V, ∼8000 A) with user-defined electric field shape as well as rapid sequences of pulses with high output quality. The circuit topology breaks the problem of simultaneous high power and switching speed into smaller, manageable portions, distributed across several identical modules. In consequence, the MPS TMS techology can use semiconductor devices with voltage and current ratings lower than the overall pulse voltage and distribute the overall switching of several hundred kilohertz among multiple transistors. MPS TMS can synthesize practically any pulse shape, including conventional ones, with fine quantization of the induced electric field (⩽17% granularity without modulation and ∼300 kHz bandwidth). Moreover, the technology allows optional symmetric differential coil driving so that the average electric potential of the coil, in contrast to conventional TMS devices, stays constant to prevent capacitive artifacts in sensitive recording amplifiers, such as electroencephalography. MPS TMS can enable the optimization of stimulation paradigms for more sophisticated probing of brain function as well as stronger and more selective neuromodulation, further expanding the parameter space available to users.
Evaluating sea ice thickness simulation is critical for projecting a summer ice-free Arctic Ocean
Authors: Zhou Xiao , Wang Bin , Huang Fei
Published: October 2022

The rapid decline of Arctic sea ice, including sea ice area (SIA) retreat and sea ice thinning, is a striking manifestation of global climate change. Analysis of 40 CMIP6 models reveals a very large spread in both model simulations of the September SIA and thickness and the timing of a summer ice-free Arctic Ocean. The existing SIA-based evaluation metrics are deficient due to observational uncertainty, prominent internal variability, and indirect Arctic response to global forcing. Given the critical roles of sea ice thickness (SIT) in determining Arctic ice variation throughout the seasonal cycle and the April SIT bridging the winter freezing and summer melting processes, we propose two SIT-based metrics, the April mean SIT and summer SIA response to April SIT, to assess climate models’ capability to reproduce the historical change of the Arctic sea ice area. The selected 11 good models reduce the uncertainty in the projected first ice-free Arctic by 70% relative to 11 poor models. The chosen models’ ensemble mean projects the first ice-free year in 2049 (2043) under the shared socio-economic pathways (SSP)2-4.5 (SSP5-8.5) scenario with one standard deviation of the inter-model spread of 12.0 (8.9) years.