bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct numerical simulation of supersonic turbulent flow with film cooling by wall-parallel blowing
Authors: Peter J. M. F. , Kloker M. J.
Published: February 2022

An advanced film-cooling application is the thermal protection of the nozzle extension of high-performance rocket engines. The extension wall needs be protected from the hot supersonic thrust gas, very much like the combustion chamber or nozzle throat region, where the flow is, however, sub- or transonic. A reliable cooling modeling for practical applications requires benchmark results for generic cases with accurate flow-field details. To this end, fundamental investigations of the interaction between the thrust and cooling gas have been performed for flat-plate flow using high-order direct numerical simulations for the first time. A cool secondary gas is injected through a vertical slot of height s in a backward-facing step. The thrust-gas flow is steam (gaseous H2O) at Mach 3.3 with a turbulent boundary layer, and a laminar supersonic stream of cool helium is injected. The influence of the coolant mass flow rate is investigated by varying the blowing ratio F or the injection height s at a fixed cooling-gas temperature and Mach number. Several previously unknown effects are found fostering correlation model evolution of the film cooling, inter alia that the upstream wall temperature needs be taken into account and how the turbulent Prandtl and Schmidt number distributions are in the field, essential for improved Reynolds-averaged Navier–Stokes simulations.
The adjustable and tunable narrowband optical absorber by insertion of the WSe2 and WS2 monolayer in symmetric and asymmetric defective photonic crystals
Authors: Ansari N. , Mohebbi E. , Nazari E.
Published: February 2022

Narrowband optical absorption plays a key role in photonic sensors and photovoltaic elements. Here, we propose a design of creating narrowband absorbers based on the symmetric and asymmetric defective photonic crystals (SDPCs and ADPCs) consisting of defects in the form of DMD in which M indicates the WS2 or WSe2 monolayer and D represents the SiO2 layer. In this paper, the effect of the defect layer thickness, polarization, and incident angle of light on the number and wavelength of defect modes in both symmetric and asymmetric structures is investigated. The findings suggest that the wavelength of the defect modes can be adjusted by varying the thickness of layer D as well as the design of the wavelength and tuned by polarization and incident angle of light. In both SDPC and ADPC, the wavelength of the defect mode shows red shift with an increase in the thickness of layer D and exhibits blue shift with an increase in the angle of light in both TE and TM polarization. This narrowband absorber demonstrates great potential for being adopted in the detection of photodetectors, absorbent filters, and the like.
Optical anisotropy of (112¯3) semipolar InGaN quantum wells homoepitaxially grown on GaN substrates
Authors: Funato Mitsuru , Matsuda Yoshinobu , Mori-Tamamura Keito , Yamaguchi Atsushi A. , Goto Hiroki , Sumida Yasunobu , Ishihara Yujiro , Kawakami Yoichi
Published: February 2022

InGaN/GaN quantum wells (QWs) are homoepitaxially grown on (112¯3) GaN substrates, and atomically smooth surfaces and abrupt InGaN/GaN interfaces are achieved. The optical anisotropy is examined using photo- and electroluminescence spectroscopies. Both methods consistently show in-plane optical polarization along the direction parallel to the projection of the c-axis on the QW plane. This polarization direction is rotated by 90° from that of unstrained, bulk InGaN, demonstrating the occurrence of polarization switching in strained, semipolar InGaN QWs. Specifically, the polarization direction is [1¯1¯22], which offers an advantage in that the {11¯00} m-planes can be used as cavity mirrors in edge-emitting lasers. The previously proposed analytical equation reasonably reproduces the experimental results.
Internal reverse-biased p–n junctions: A possible origin of the high resistance in chalcogenide superlattice for interfacial phase change memory
Authors: Li Bowen , Xu Longlong , Guo Yuzheng , Li Huanglong
Published: February 2022

Chalcogenide superlattice (CSL) is one of the emerging material technologies for ultralow-power phase change memories. However, the resistance switching mechanism of the CSL-based device is still hotly debated. Early electrical measurements and recent materials characterizations have suggested that the Kooi-phase CSL is very likely to be the as-fabricated low-resistance state. Due to the difficulty in in situ characterization at atomic resolution, the structure of the electrically switched CSL in its high-resistance state is still unknown and mainly investigated by theoretical modelings. So far, there has been no simple model that can unify experimental results obtained from device-level electrical measurements and atomic-level materials characterizations. In this work, we carry out atomistic transport modelings of the CSL-based device and propose a simple mechanism accounting for its high resistance. The modeled high-resistance state is based on the interfacial SbTe bilayer flipped CSL that has previously been mistaken for the low-resistance state. This work advances the understanding of CSL for emerging memory applications.
Medium-range structure motifs of complex iron oxides
Authors: Huang Shengxuan , Hu Qingyang
Published: February 2022

Natural occurring iron oxides, such as Fe2O3, Fe3O4, and FeO, are abundant on Earth's surface and feature many implications in our daily life since the Iron Age, the final epoch of the prehistory of humanity. The physics of iron oxides is at the frontier of physical research due to their complicated magnetic and electronic properties. What makes it even more intriguing is the introduction of pressure, which not only regulates the crystal structures and physical properties, but also creates new iron-oxide stoichiometry. Recent studies discovered several novel iron-oxygen compounds under various pressure–temperature conditions. Despite different Fe/O ratios, those iron oxides are built upon similar structural units including FeO6 octahedra and trigonal prisms. Complex stoichiometry of pressurized iron oxides is built up by stacking layers of those FeO6 units, and in the medium-range, they are organized by certain structural motifs. In this perspective, we go beyond conventional iron-oxygen binary compounds and reveal the general formation mechanism of complex iron oxide crystals under high-pressure conditions. The results will be helpful for summarizing literary works of iron oxides and exploring novel stoichiometry with optimal physical properties.
Research on dual-functional characteristics of piezoelectric metamaterial beams for vibration reduction and power generation
Authors: Wang Xingguo , Wang Lan , Shu Haisheng , Zhang Lei
Published: February 2022

A piezoelectric metamaterial beam composed of metamaterials and piezoelectric energy harvesting is proposed to realize the dual-functional characteristics of vibration reduction and power generation simultaneously. Based on the theoretical derivation of the electrical domain and the structural domain, the transfer matrix of the piezoelectric metamaterial beam is constructed using the charge accurate integration method and the transfer matrix method. The energy band structure of the infinite periodical model and the vibration transmission of the finite periodical model are analyzed numerically to illustrate the low frequency bandgaps of the piezoelectric metamaterial beam. An external load circuit for energy harvesting is introduced, and its influence on the vibration characteristics of the original system is analyzed. On this basis, Kirchhoff’s law is used to derive accurate analytical solutions for the output voltage and output power of each piezoelectric oscillator, and the relationship between the local resonance bandgap and band-edge effect and the power generation performance of the piezoelectric metamaterial beam is investigated in detail. Finally, the theoretical analysis results are verified by finite element simulation analysis. It is shown that the introduction of an external load circuit for energy harvesting results in the vanishing of the dense resonant frequency range at the lower band edge of the local resonance bandgap and the modal peaks near the upper and lower band edges are effectively suppressed, consequently expanding the range of the bandgap. In addition, an excellent power generation performance is observed in the local resonant bandgap and the passband of the upper and lower band edges.
Do not forget the Rydberg orbitals
Authors: Simons Jack
Published: February 2022

Within any molecule or cluster containing one or more positively charged sites, families of Rydberg orbitals exist. Free electrons can attach directly, and anionic reagents with low electron binding energy can transfer an electron into one of these orbitals to form a neutral Rydberg radical. The possibilities that such a radical could form a covalent bond either to another Rydberg radical or to a radical holding its electron in a conventional valence orbital are considered. This Perspective overviews two roles that Rydberg radicals can play, both of which have important chemical consequences. Attachment of an electron into excited Rydberg orbitals is followed by rapid (∼10−6 s) relaxation into the lowest-energy Rydberg orbital to form the ground state radical. Although the excited Rydberg species are stable with respect to fragmentation, the ground-state species is usually quite fragile and undergoes homolytic bond cleavage (e.g., –R2NH dissociates into –R2N + H or into –RNH + R) by overcoming a very small barrier on its potential energy surface, thus generating reactive radicals (H or R). Here, it is shown that as a result of this fragility, any covalent bonds formed by Rydberg radicals are weak and the molecules they form are susceptible to exothermic fragmentations that involve quite small activation barriers. Another role played by Rydberg species arises when the Coulomb potentials provided by the (one or more) positive site(s) in the molecule stabilize low-energy anti-bonding orbitals (e.g., σ* orbitals of weak σ bonds or low-lying π* orbitals) to the extent that electron attachment into these Coulomb-stabilized orbitals is rendered exothermic. In such cases, the overlap of the Rydberg orbitals on the positive site(s) with the σ* or π* orbitals allows either a free electron or a weakly bound electron to an anionic reagent that is attracted toward the positive site by its Coulomb force to be guided/transferred into the σ* or π* orbital instead. After attaching to such an anti-bonding orbital, bond cleavage occurs again, generating reactive radical species. Because of the large radial extent of Rydberg orbitals, this class of bond cleavage events can occur quite distant from the positively charged group. In this Perspective, several examples of both types of phenomena are given for illustrative purposes.
Forest fire and its key drivers in the tropical forests of northern Vietnam
Authors: Trang P. T. , Andrew M. E. , Chu T. , Enright N. J.
Published: February 2022

Fire increasingly threatens tropical forests in northern Vietnam as climate changes and human population grows. Understanding fire occurrence patterns may support more effective forest management and reduce fire risk. We investigated spatiotemporal patterns and drivers of wildfire across three provinces in northern Vietnam and assessed the effectiveness of the Modified Nesterov index (MNI) fire danger rating system. We explored fire occurrence and size within and between years and forest types using descriptive analyses and developed spatiotemporal Maximum Entropy (Maxent) models incorporating variables representing potential drivers of fire, including weather, fuel, topography and human activity. Most fires occurred late in the dry season and fires were most common in natural forest. Maxent models successfully predicted fire occurrence (area under the receiver operating characteristic curve (AUC) values 0.67–0.79). While the contributions of drivers varied among provinces, MNI, temperature, elevation and distance to road were consistently important. The model for combined provinces showed that fire probability was greater under higher temperature and MNI, in areas with lower population, farther from roads, at higher elevations and in natural forests. This study suggests that an assessment integrating multiple drivers better predicts fire occurrence than a system based on weather alone and may support improved fire management and education in northern Vietnam.
Affinity maturation for an optimal balance between long-term immune coverage and short-term resource constraints
Authors: Chardès Victor , Vergassola Massimo , Walczak Aleksandra M. , Mora Thierry
Published: February 2022

Significance

Humoral immunity relies on the mutation and selection of B cells to better recognize pathogens. This affinity maturation process produces cells with diverse recognition capabilities. Examining optimal immune strategies that maximize the long-term immune coverage at a minimal metabolic cost, we show when the immune system should mount a de novo response rather than rely on existing memory cells. Our theory recapitulates known modes of the B cell response, predicts the empirical form of the distribution of clone sizes, and rationalizes as a trade-off between metabolic and immune costs the antigenic imprinting effects that limit the efficacy of vaccines (original antigenic sin). Our predictions provide a framework to interpret experimental results that could be used to inform vaccination strategies.
Using beat frequency in music to adjust running cadence in recreational runners: A randomized multiple baseline design
Authors: te Brake Mark , Stolwijk Niki , Staal Bart , Van Hooren Bas
Published: February 2022

Running with music has been shown to acutely change cadence. However, it is unclear if the increased cadence remains long‐term when running without music in an in‐field situation. The aim of this 12‐week study was to investigate the effect of a 4‐week music running program on cadence, speed and heartrate during and after the music running program. Seven recreational runners with a cadence of <170 steps per minute were randomly assigned to a baseline and post‐intervention period of different durations. During the intervention phase, the participants ran with a musical beat that was 7.5–10% higher than their mean cadence at the start of the study. Cadence, heartrate and running speed were measured twice a week during a 5‐kilometer run with a watch, and were analyzed using randomization tests and visual data inspection. Two participants dropped‐out due to shortage of time (n = 1) and an acute calf injury (n = 1). Cadence significantly increased during the intervention period (+8.5%), and remained elevated during the post‐intervention period (+7.9% (p = .001)) in comparison with the baseline period. Heartrate and running speed did not significantly change during any period. This study among five participants shows that four weeks of running with a musical beat that is 7.5–10% higher than the preferred cadence may be an effective and feasible intervention to increase running cadence. Importantly, the increased cadence occurred without simultaneous increases in running speed and heartrate, hereby potentially reducing mechanical loading without increasing metabolic load.

Highlights

Running with a musical rhythm that is higher than the preferred cadence leads to an increased running cadence, without increasing heartrate and running speed.

This cadence remains elevated for at least three to five weeks after the music intervention period.

All individuals showed a practically relevant increase in cadence during and after the intervention.
Consistent truncations around half-maximal AdS5 vacua of 11-dimensional supergravity
Authors: Malek Emanuel , Vall Camell Valentí
Published: February 2022

We use exceptional field theory to systematically study all possible consistent truncations around any M-theory half-maximal vacua of the warped product form AdS5 × M
3 × S
2 × S
1, with M
3 a three-dimensional manifold. We show that, for any of these vacua, only truncations with at most three vector multiplets are consistent. Furthermore, the possible gaugings are restricted to be either SU(2) × U(1) or ISO(3) × U(1) where, in the first case, the U(1) factor can have different embeddings inside the global symmetry group SO(5, n), where n ⩽ 3 equals the number of vector multiplets. This rules out the possibility of any other gauging arising as a consistent truncation around the aforementioned M-theory vacua. Our analysis shows that of the many flows from half-maximal to quarter-maximal AdS5 vacua constructed in five-dimensional supergravity in Bobev (2018 J. High Energy Phys.
6 86), only those corresponding to an adjoint mass deformation in the dual SCFT can be uplifted to 11-dimensional supergravity. The other flows are five-dimensional artefacts without a higher-dimensional origin. Furthermore, consistent truncations with vector multiplets exist only if the vacuum satisfies certain conditions, which we derive.
Hanging a capacitor plate from a spring: a coupled mechanical–electromagnetic oscillator
Authors: Mungan Carl E , Lipscombe Trevor C
Published: February 2022

A pair of coupled nonlinear differential equations describes the oscillations in the position and charge of one of the disks of a parallel-plate capacitor hanging from a spring, if the capacitor is initially charged and then connected to an inductor. For realistic values of the parameters, the results are well-approximated by Mathieu functions wherein the rapid charge oscillations are simultaneously modulated in amplitude and frequency by the slow position oscillations of the plate.
Design of a lattice dielectric cylinder based on multiwalled carbon nanotube-epoxy composite for microwave absorption in the X-band
Authors: Liu Yutong , Zhou Yuhao , Si Kaixuan , Bie Shaowei , Jiang Jianjun
Published: February 2022

To meet the urgent electromagnetic compatibility (EMC) requirements for the electronic products, microwave absorbers with a lattice of the dielectric cylinder were investigated. The elements of the lattice have a cylindrical shape and are composites of epoxy resin filled with multi-walled carbon nanotubes (MWCNTs-EP). The relative complex permittivity of the MWCNT-EP was obtained from the S-parameters measured by the transmission-reflection method with X-band waveguide. The numerical simulation results show that the reflection coefficient of the uniform lattice of the dielectric cylinder is less than −10 dB in the entire X-band (8 GHz–12 GHz) and the reflection coefficient of the hybrid lattice of the dielectric cylinder (HLDC) is less than −15 dB in the same band. Moreover, the reflection coefficient of HLDC is less than −20 dB at normal incidence in the frequency range of 8.4 GHz–11.3 GHz. Further investigation demonstrates that the proposed HLDC could maintain good absorption performance under different incident angles and polarizations. This study suggests that HLDC with the characteristics of lightweight, excellent absorption performance, good angle, and polarization stability provide a promising prospect in the EMC field.
Study of microsecond X-pinches of refractory and non-refractory metals
Authors: Andola Sanjay Chandra , Jaiswar Ashutosh Chandrajeet , Kaushik Trilok Chand , Joshi Keshaw Datt
Published: February 2022

In this report, we present a comparative study on the properties of x-rays from X-pinches made of two groups of metallic wires. The results were obtained on a small current driver having dI/dt of 0.04–0.11 kA ns−1. The X-pinches made of refractory (Mo and W) and non-refractory (Al and Cu) wires were studied for the current required to pinch and their x-ray parameters such as x-ray yield, timing, jitter, number of bursts, and source size. It has been observed that despite lower linear mass density, the Cu group requires a higher current for plasma to pinch than the W group X-pinches. For a given configuration, a faster current compresses the plasma at a higher current which leads to comparatively higher x-ray yield. Substantial enhancement in the quality of x-rays has also been observed in wires with few micron thick dielectric coating. The results of this work can be useful in the development of a small capacitive X-pinch system suitable for studies related to high energy density physics.
Characterization of phonon thermal transport of Ti3C2T
x
MXene thin film
Authors: Wu Hao , Gu Jiaxin , Li Zhongcheng , Liu Wenxiang , Bao Hua , Lin Huan , Yue Yanan
Published: February 2022

Two-dimensional MXene materials with high electrotonic conductivity, good chemical stability, and unique laminar structure show great potential in the field of electrochemistry. In contrast to the widely concerned electrical properties, studies on the thermal properties of MXene materials are very limited. This paper presents a comprehensive analysis of the thermal properties of Ti3C2T
x
MXene thin film. Thermal diffusivity and thermal conductivity of Ti3C2T
x
films are characterized by the transient electro-thermal technique. The experimental results show a 16% enhancement in thermal conductivity when the temperature is increased from 307 K to 352 K. The phonon transport contributes substantially to thermal conductivity compared with electron transport. Molecular dynamic simulation is employed to further investigate the role of phonon thermal transport of Ti3C2 layer. It is found that the combined effect of specific heat capacity, stacking structure and internal stress states is responsible for the thermal transport performance of Ti3C2T
x
MXene thin film.
Non-Markovian systems out of equilibrium: exact results for two routes of coarse graining
Authors: Jung Gerhard
Published: February 2022

Generalized Langevin equations (GLEs) can be systematically derived via dimensional reduction from high-dimensional microscopic systems. For linear models the derivation can either be based on projection operator techniques such as the Mori–Zwanzig (MZ) formalism or by ‘integrating out’ the bath degrees of freedom. Based on exact analytical results we show that both routes can lead to fundamentally different GLEs and that the origin of these differences is based inherently on the non-equilibrium nature of the microscopic stochastic model. The most important conceptional difference between the two routes is that the MZ result intrinsically fulfills the generalized second fluctuation–dissipation theorem while the integration result can lead to its violation. We supplement our theoretical findings with numerical and simulation results for two popular non-equilibrium systems: time-delayed feedback control and the active Ornstein–Uhlenbeck process.
Probing borophene oxidation at the atomic scale
Authors: Liu Xiaolong , Rahn Matthew S , Ruan Qiyuan , Yakobson Boris I , Hersam Mark C
Published: February 2022

Two-dimensional boron (i.e. borophene) holds promise for a variety of emerging nanoelectronic and quantum technologies. Since borophene is synthesized under ultrahigh vacuum (UHV) conditions, it is critical that the chemical stability and structural integrity of borophene in oxidizing environments are understood for practical borophene-based applications. In this work, we assess the mechanism of borophene oxidation upon controlled exposure to air and molecular oxygen in UHV via scanning tunneling microscopy andspectroscopy, x-ray photoelectron spectroscopy, and density functional theory calculations. While borophene catastrophically degrades almost instantaneously upon exposure to air, borophene undergoes considerably more controlled oxidation when exposed to molecular oxygen in UHV. In particular, UHV molecular oxygen dosing results in single-atom covalent modification of the borophene basal plane in addition to disordered borophene edge oxidation that shows altered electronic characteristics. By comparing these experimental observations with density functional theory calculations, further atomistic insight is gained including pathways for molecular oxygen dissociation, surface diffusion, and chemisorption to borophene. Overall, this study provides an atomic-scale perspective of borophene oxidation that will inform ongoing efforts to passivate and utilize borophene in ambient conditions.
Relating boundary and interior solutions of the cohomological equation for cocycles by isometries of negatively curved spaces. The Lǐsic case*
Authors: Moraga Alexis , Ponce Mario
Published: February 2022

We consider the reducibility problem of cocycles by isometries of Gromov hyperbolic metric spaces in the Lǐsic setting. We show that provided that the boundary cocycle (that acts on a compact space) is reducible in a suitable Hölder class, then the original cocycle by isometries (that acts on an unbounded space) is also reducible.
A systematic review of conversion factors between kerma-area product and effective/organ dose for cardiac interventional fluoroscopy procedures performed in adult and paediatric patients
Authors: Brambilla Marco , D’Alessio Andrea , Kuchcinska Agnieszka , Segota Doris , Sukupova Lucie
Published: February 2022

The aim of this systematic review is to undertake a critical appraisal of the evidence in the published literature concerning the conversion factors between kerma-area product (P
KA) and effective/organ dose (DCED_PKA, DCHT_PKA) for cardiac interventional fluoroscopy procedures performed in adults and paediatric patients and to propose reference conversion factors to help standardize dose calculations. A search strategy utilizing MeSH headings in three databases identified 59 (adult) and 37 (paediatric) papers deemed eligible for the review. Exclusion criteria were adopted to select data only from publications which established DCED_PKA in patients using the ICRP 103 tissue weighting factors. A time restriction from January 2007 was introduced in the search to capture the evolving trends of utilization of fluoroscopy-guided intervention technologies only in recent years. The suggested DCED_PKA and DCHT_PKA were synthesized by calculating the weighted averages of the values reported by the authors with weights corresponding to the study sample size. Eighteen studies for both adult (9) and paediatric (9) patients matching the search terms fulfilled the inclusion criteria. The suggested value for DCED_PKA in adult patients amounts to 0.24 mSv Gy−1cm−2. The suggested values for DCHT_PKA ranged from a minimum of 0.15 mSv Gy−1cm−2 for the female breast to a maximum of 0.97 mSv Gy−1cm−2 for the lungs. The suggested values for DCED_PKA in paediatric patients ranged from 3.45 mSv Gy−1cm−2 for the new-born to 0.49 mSv Gy−1cm−2 in the 15 years age class. The suggested values for DCHT_PKA ranged from a minimum of 0.33 mSv Gy−1cm−2 for bone marrow in the 15 years age class to a maximum of 11.49 mSv Gy−1cm−2 for the heart in the new-born. To conclude, values of DCED_PKA/DCHT_PKA were provided for calculating effective/organ doses in cardiac interventional procedures. They can be useful for standardizing dose calculations, hence for comparison of the radiation detriment from different imaging procedures and in the framework of epidemiologic studies.
Line identification of extreme ultraviolet (EUV) spectra from iron, copper and molybdenum ions in EAST tokamak
Authors: Zhang Wenmin , Zhang Ling , Cheng Yunxin , Morita Shigeru , Wang Zhengxiong , Hu Ailan , Zhang Fengling , Duan Yanmin , Zhou Tianfu , Wang Shouxin , Liu Haiqing
Published: February 2022

Extreme ultraviolet (EUV) spectra emitted from iron and copper ions in a range of 8–500 Å and molybdenum ions in a range of 8–400 Å were measured in Experimental Advanced Superconducting Tokamak (EAST) discharges accompanied with spontaneous sputtering events, by which metallic impurity influxes are suddenly increased in the discharge. Several spectral lines from L-, M-, and N-shell partially ionized ions have been successfully observed with two EUV spectrometers named EUV_Short and EUV_Long working in wavelength ranges of 8–130 Å and 20–500 Å, respectively. The wavelength position is accurately calibrated in-situ based on several well-known spectra of low-Z impurity ions. The line identification is carefully performed based on the National Institute of Standards Technology (NIST) database and previously published experimental data. As a result, it is found that B-, Be-, and Li-like iron and copper spectra Al-, Mg-, and Na-like molybdenum spectra appear in discharges with high central electron temperature (>1.8 keV). The highest ionization stages identified here are Li-like iron and copper and Na-like molybdenum, e.g. Fe XXIV at 192.028 Å (1s22p 2P3/2 → 1s22s 2S1/2), Cu XXVII at 153.513 Å (1s22p 2P3/2 → 1s22s 2S1/2) and Mo XXXII at 127.868 Å (2p63p 2P3/2 → 2p63s 2S1/2). Two unresolved transition arrays of molybdenum ions (Mo-UTAs) appear at wavelength ranges of 15–30 Å and 65–95 Å, and are preliminarily identified as Mo XX-Mo XXXII and Mo XVII-Mo XXXII, respectively. In addition, six spectral lines are newly found by comparing a time evolution of the line intensity from impurity ions in different ionization stages, i.e. Fe XVIII at 17.60 ± 0.02 Å, Cu XXI at 13.15 ± 0.02 Å, Cu XVIII at 260.32 ± 0.07 Å, Cu XVIII at 261.00 ± 0.06 Å, Mo XXVIII at 85.30 ± 0.03 Å and Mo XXIX at 89.59 ± 0.03 Å. The wavelengths of EUV spectra identified in this work are summarized in tables with transitions for each impurity species.
Sensitivity of the Roman Coronagraph Instrument to Exozodiacal Dust
Authors: Douglas Ewan S. , Debes John , Mennesson Bertrand , Nemati Bijan , Ashcraft Jaren , Ren Bin , R. Stapelfeldt Karl , Savransky Dmitry , Lewis Nikole K. , Macintosh Bruce
Published: February 2022

Exozodiacal dust, warm debris from comets and asteroids in and near the habitable zone of stellar systems, reveals the physical processes that shape planetary systems. Scattered light from this dust is also a source of background flux which must be overcome by future missions to image Earthlike planets. This study quantifies the sensitivity of the Nancy Grace Roman Space Telescope Coronagraph to light scattered by exozodi, the zodiacal dust around other stars. Using a sample of 149 nearby stars, previously selected for optimum detection of habitable exoplanets by space observatories, we find the maximum number of exozodiacal disks with observable inner habitable zone boundaries is six and the number of observable outer habitable boundaries is 74. One zodi was defined as the visible-light surface brightness of 22 m
V arcsec−2 around a solar-mass star, approximating the scattered light brightness in visible light at the Earth-equivalent insolation. In the speckle limited case, where the signal-to-noise ratio is limited by speckle temporal stability rather than shot noise, the median 5σ sensitivity to habitable zone exozodi is 12 zodi per resolution element. This estimate is calculated at the inner-working angle of the coronagraph, for the current best estimate performance, neglecting margins on the uncertainty in instrument performance and including a post-processing speckle suppression factor. For an log-norm distribution of exozodi levels with a median exozodi of 3× the solar zodi, we find that the Roman Coronagraph would be able to make 5σ detections of exozodiacal disks in scattered light from 13 systems with a 95% confidence interval spanning 7–20 systems. This sensitivity allows Roman Coronagraph to complement ground-based measurements of exozodiacal thermal emission and constrain dust albedos. Optimized post-processing and detection of extended sources in multiple resolution elements is expected to further improve this unprecedented sensitivity to light scattered by exozodiacal dust.
Heterogeneous integration of GaSb layer on (100) Si substrate by ion-slicing technique
Authors: Liu Ren-Jie , Lin Jia-Jie , Shen Zheng-Hao , Sun Jia-Liang , You Tian-Gui , Li Jin , Liao Min , Zhou Yi-Chun
Published: February 2022

Integration of the high-quality GaSb layer on an Si substrate is significant to improve the GaSb application in optoelectronic integration. In this work, a suitable ion implantation fluence of 5 × 1016-cm−2 H ions for GaSb layer transfer is confirmed. Combining the strain change and the defect evolution, the blistering and exfoliation processes of GaSb during annealing is revealed in detail. With the direct wafer bonding, the GaSb layer is successfully transferred onto a (100) Si substrate covered by 500-nm thickness thermal oxide SiO2 layer. After being annealed at 200 °C, the GaSb layer shows high crystalline quality with only 77 arcsec for the full width at half maximum (FWHM) of the x-ray rocking curve (XRC).
Effect of conical intersection of benzene on non-adiabatic dynamics
Authors: Li Duo-Duo , Zhang Song
Published: February 2022

The effect of conical intersection on the excited dynamics of benzene is studied by ab initio theory of electronic structure, which provides an important insight into photophysical and photochemical reactions. Based on the CASSCF(6,6)/6-31+G(d, p) method, the topological structures of conical intersections S1/S and S2/S1 of benzene, as well as the optimal structures of the ground state (S) and excited states (S1, S2), are determined. The energy minima of the S1 state and S2 state are estimated at 4.608 eV and 6.889 eV, respectively. In addition, the energy values of the conical intersections of S1/S and S2/S1 are predicted to be 5.600 eV and 6.774 eV. According to the topological structures and energy values of the S2/S1 and S1/S conical intersections, the photophysical behavior of benzene excited to the S2 state and the effects of the S2/S1 and S1/S conical intersections are discussed in detail.
Synchronization of nanowire-based spin Hall nano-oscillators
Authors: Jiang Biao , Zhang Wen-Jun , Alam Mehran Khan , Yu Shu-Yun , Han Guang-Bing , Liu Guo-Lei , Yan Shi-Shen , Kang Shi-Shou
Published: February 2022

The synchronization of the spin Hall nano-oscillator (SHNO) device driven by the pure spin current has been investigated with micromagnetic simulations. It was found that the power spectra of nanowire-based SHNO devices can be synchronized by varying the current flowing in the heavy metal (HM) layer. The synchronized signals have relatively high power and narrow linewidth, favoring the potential applications. We also found that the synchronized spectra are strongly dependent on both the number and length of nanowires. Moreover, a periodic modulation of power spectra can be obtained by introducing interfacial Dzyaloshinskii–Moriya interaction (iDMI). Our findings could enrich the current understanding of spin dynamics driven by the pure spin current. Further, it could help to design novel spintronic devices.
Half-metallicity induced by out-of-plane electric field on phosphorene nanoribbons
Authors: Ouyang Xiao-Fang , Wang Lu
Published: February 2022

Exploring the half-metallic nanostructures with large band gap and high carrier mobility is a crucial solution for developing high-performance spintronic devices. The electric and magnetic properties of monolayer zigzag black-phosphorene nanoribbons (ZBPNRs) with various widths are analyzed by means of the first-principles calculations. Our results show that the magnetic ground state is dependent on the width of the nanoribbons. The ground state of narrow nanoribbons smaller than 8ZBPNRs prefers ferromagnetic order in the same edge but antiferromagnetic order between two opposite edges. In addition, we also calculate the electronic band dispersion, density of states and charge density difference of 8ZBPNRs under the action of out-of-plane electric field. More interesting, the addition of out-of-plane field can modulate antiferromagnetic semiconductor to the half metal by splitting the antiferromagnetic degeneracy. Our results propose a new approach to realize half-metal in phosphorene, which overcomes the drawbacks of graphene/silicene with negligible band gap as well as the transitional metal sulfide (TMS) with low carrier mobility.
Force-constant-decayed anisotropic network model: An improved method for predicting RNA flexibility
Authors: Wang Wei-Bu , Li Xing-Yuan , Su Ji-Guo
Published: February 2022

RNA is an important biological macromolecule, which plays an irreplaceable role in many life activities. RNA functions are largely determined by its tertiary structure and the intrinsic dynamics encoded in the structure. Thus, how to effective extract structure-encoded dynamics is of great significance for understanding RNA functions. Anisotropic network model (ANM) is an efficient method to investigate macromolecular dynamical properties, which has been widely used in protein studies. However, the performance of the conventional ANM in describing RNA flexibility is not as good as that on proteins. In this study, we proposed a new approach, named force-constant-decayed anisotropic network model (fcd-ANM), to improve the performance in investigating the dynamical properties encoded in RNA structures. In fcd-ANM, nucleotide pairs in RNA structure were connected by springs and the force constant of springs was decayed exponentially based on the separation distance to describe the differences in the inter-nucleotide interaction strength. The performance of fcd-ANM in predicting RNA flexibility was evaluated using a non-redundant structure database composed of 51 RNAs. The results indicate that fcd-ANM significantly outperforms the conventional ANM in reproducing the experimental B-factors of nucleotides in RNA structures, and the Pearson correlation coefficient between the predicted and experimental nucleotide B-factors was distinctly improved by 21.05% compared to the conventional ANM. Fcd-ANM can serve as a more effective method for analysis of RNA dynamical properties.
All-fiber erbium-doped dissipative soliton laser with multimode interference based on saturable-reserve saturable hybrid optical switch
Authors: Zhao Xin , Wan Renyan , Li Weiyan , Jin Liang , Zhang He , Li Yan , Xu Yingtian , Shi Linlin , Ma Xiaohui
Published: February 2022

Reverse saturable absorption is essential for the realization of dissipative solitons. In this paper, we introduce reverse saturable absorption by using nonlinear multimode interference (NL-MMI), for the first time, to the best of our knowledge, and obtain a stable dissipative soliton operation. By adjusting the coupling efficiency from multimode fiber to single mode fiber, the absorption properties of NL-MMI can be switched between saturation and reverse saturation. The dissipative soliton can be obtained with pulse width of 975 fs in the experiment, the 3-dB bandwidth at 1555 nm is 16 nm, and the maximum output power is 11.48 mW. The nonlinear absorption optical modulation and high damage threshold characteristics of the NL-MMI based ultrafast optical switch provide a new idea for realizing dissipative solitons.
Characterization of topological phase of superlattices in superconducting circuits
Authors: Chen Jianfei , Wu Chaohua , Fan Jingtao , Chen Gang
Published: February 2022

The recent experimental observation of topological magnon insulator states in a superconducting circuit chain marks a breakthrough for topological physics with qubits, in which a dimerized qubit chain has been realized. Here, we extend such a dimer lattice to superlattice with arbitrary number of qubits in each unit cell in superconducting circuits, which exhibits rich topological properties. Specifically, by considering a quadrimeric superlattice, we show that the topological invariant (winding number) can be effectively characterized by the dynamics of the single-excitation quantum state through time-dependent quantities. Moreover, we explore the appearance and detection of the topological protected edge states in such a multiband qubit system. Finally, we also demonstrate the stable Bloch-like-oscillation of multiple interface states induced by the interference of them. Our proposal can be readily realized in experiment and may pave the way towards the investigation of topological quantum phases and topologically protected quantum information processing.
Valley-dependent transport in strain engineering graphene heterojunctions
Authors: Wan Fei , Wang X R , Liao L H , Zhang J Y , Chen M N , Zhou G H , Siu Z B , Jalil Mansoor B. A. , Li Yuan
Published: February 2022

We study the effect of strain on band structure and valley-dependent transport properties of graphene heterojunctions. It is found that valley-dependent separation of electrons can be achieved by utilizing strain and on-site energies. In the presence of strain, the values of transmission can be effectively adjusted by changing the strengths of the strain, while the transport angle basically keeps unchanged. When an extra on-site energy is simultaneously applied to the central scattering region, not only are the electrons of valleys K and K′ separated into two distinct transmission lobes in opposite transverse directions, but the transport angles of two valleys can be significantly changed. Therefore, one can realize an effective modulation of valley-dependent transport by changing the strength and stretch angle of the strain and on-site energies, which can be exploited for graphene-based valleytronics devices.
Influence of particle size on the breaking of aluminum particle shells
Authors: Wang Tian-Yi , Zhou Zheng-Qing , Peng Jian-Ping , Gao Yu-Kun , Zhang Ying-Hua
Published: February 2022

Rupturing the alumina shell (shell-breaking) is a prerequisite for releasing energy from aluminum powder. Thermal stress overload in a high-temperature environment is an important factor in the rupture of the alumina shell. COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron-scale aluminum particles with different particle sizes at 650 °C in vacuum. The simulation results show that the thermal stability time and shell-breaking response time of 10 μm–100 μm aluminum particles are 0.15 μs–11.44 μs and 0.08 μs–3.94 μs, respectively. They also reveal the direct causes of shell breaking for aluminum particles with different particle sizes. When the particle size is less than 80 μm, the shell-breaking response is a direct result of compressive stress overload. When the particle size is between 80 μm and 100 μm, the shell-breaking response is a direct result of tensile stress overload. This article provides useful guidance for research into the energy release of aluminum powder.
RETRACTED: Structural, magnetic properties, critical behaviors and magnetic entropy changes of La0.7-x
Gd
x
Ca0.3MnO3 (x=0, 0.05, 0.1) manganites
Authors: Zhou Min , Jin Xiang , Wang WenXing , Zheng Lin , Xing Ru , Lu Yi , Zhao JianJun
Published: February 2022

Structural, magnetic properties, critical behaviors and magnetic entropy changes of La0.7-x
Gd
x
Ca0.3MnO3 (x=0, 0.05, 0.1) polycrystalline manganites have been investigated. The X-ray diffraction characterization shows that all the samples can be well indexed on an orthorhombic structure with Pnma space group. Magnetic measurements show that polycrystalline samples sequentially display the characteristics of cluster spin glass states, ferromagnetic states, ferromagnetic paramagnetic coexistence states and pure paramagnetic states with increasing temperature. The Curie temperature (Tc) increases with increasing doping concentration x, and the ferromagnetic paramagnetic transform into a second-order phase transitions near the Tc. Critical behaviors have been studied through the modified Arrott plots and the Kouvel-Fisher method. The critical exponents of polycrystalline samples are determined to be close to the critical exponents of the tricritical mean field model (x=0), 3D Ising model (x=0.05) and 3D Heisenberg model (x=0.1), indicating that their ferromagnetic coupling may be the result of the short-range interactions between spins in this system. The maximum magnetic entropy changes reach values of 3.99 J/(kg·K), 2.81 J/(kg·K) and 4.20 J/(kg·K) at the magnetic field of 7T, and the relative cooling power (RCP) values of La0.7-x
Gd
x
Ca0.3MnO3 (x=0, 0.05, 0.1) are 478.8 J/kg, 431.1 J/kg and 536.98 J/kg respectively.
On the masses of A = 54 isospin septet and the isobaric multiplet mass equation *
Authors: Li Hong-Fu , Xu Xing , Wang Meng , Zhang Yu-Hu , Fu Chao-Yi , Huang Wen-Jia
Published: February 2022

Using the ground-state mass of 52Ni and two-proton decay energy of 54Zn, the ground-state mass excess of 54Zn is deduced to be –6504(85) keV. This value is about 2 MeV lower than the prediction of the quadratic form of the isobaric multiplet mass equation (IMME). A cubic fit to the existing mass data of the

,

isospin multiplet yields a surprisingly large d coefficient of IMME, i.e.,

, being

deviated from zero, and the resultant

ratio significantly deviates from the systematics. This phenomenon is analyzed in this study, and we conclude that the breakdown of the quadratic form of IMME could be likely due to the mis-assignment of the

isobaric analog state (IAS) in the

nucleus 54Fe or extremely strong isospin mixing.
Effects of a kaonic meson on the ground-state properties of nuclei *
Authors: Guo Jing , Chen D. H. , Zhou Xian-Rong , Chen Q. B. , Schulze H.-J.
Published: February 2022

The effects of an additional

meson on the ground-state properties of nuclei are investigated within an axially-deformed Skyrme-Hartree-Fock approach combined with a Skyrme-type kaon-nucleon interaction. The

meson increases the binding energies of all nuclei, whereas it affects deformations only for light nuclei without shell closure. The nucleon drip lines are modified due to the strongly attractive

interaction. This is attributed to the behavior of the highest-occupied nucleon single-particle levels near the drip lines, which is analyzed in detail.
Defects properties and vacancy diffusion in Cu2MgSnS4
Authors: Tse Kin Fai , Wang Shengyuan , Wong Man Hoi , Zhu Junyi
Published: February 2022

Cu2ZnSnS4 (CZTS) is a promising photovoltaic absorber material, however, efficiency is largely hindered by potential fluctuation and a band tailing problem due to the abundance of defect complexes and low formation energy of an intrinsic CuZn defect. Alternatives to CZTS by group I, II, or IV element replacement to circumvent this challenge has grown research interest. In this work, using a hybrid (HSE06) functional, we demonstrated the qualitative similarity of defect thermodynamics and electronic properties in Cu2MgSnS4 (CMTS) to CZTS. We show SnMg to be abundant when in Sn- and Cu-rich condition, which can be detrimental, while defect properties are largely similar to CZTS in Sn- and Cu-poor. Under Sn- and Cu-poor chemical potential, there is a general increase in formation energy in most defects except SnMg, CuMg remains as the main contribution to p-type carriers, and SnMg may be detrimental because of a deep defect level in the mid gap and the possibility of forming defect complex SnMg+MgSn. Vacancy diffusion is studied using generalized gradient approximation, and we find similar vacancy diffusion properties for Cu vacancy and lower diffusion barrier for Mg vacancy, which may reduce possible Cu-Mg disorder in CMTS. These findings further confirm the feasibility of CMTS as an alternative absorber material to CZTS and suggest the possibility for tuning defect properties of CZTS, which is crucial for high photovoltaic performance.