bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband, millimeter-wave anti-reflective structures on sapphire ablated with femto-second laser
Authors: Takaku R. , Hanany S. , Imada H. , Ishino H. , Katayama N. , Komatsu K. , Konishi K. , Kuwata-Gonokami M. , Matsumura T. , Mitsuda K. , Sakurai H. , Sakurai Y. , Wen Q. , Yamasaki N. Y. , Young K. , Yumoto J.
Published: December 2020

We designed, fabricated, and measured anti-reflection coating (ARC) on sapphire that has 116% fractional bandwidth and transmission of at least 97% in the millimeter wave band. The ARC was based on patterning pyramid-like sub-wavelength structures (SWS) using ablation with a 15 W femto-second laser operating at 1030 nm. One side of each of two disks was fabricated with SWS that had a pitch of 0.54 mm and a height of 2 mm. The average ablation volume removal rate was 1.6 mm3/min. Measurements of the two-disk sandwich show transmission higher than 97% between 43 and 161 GHz. We characterize instrumental polarization (IP) arising from differential transmission due to asymmetric SWS. We find that with proper alignment of the two-disk sandwich, RMS IP across the band is predicted to be 0.07% at normal incidence and less than 0.6% at incidence angles up to 20°. These results indicate that laser ablation of SWS on sapphire and on other hard materials such as alumina is an effective way to fabricate broadband ARC.
Blow-up issues for the weakly dissipative periodic b-family of equations revisited
Authors: Dong Xiaofang
Published: December 2020

In this paper, we study the weakly dissipative asymptotically equivalent shallow water wave equations on the circle, which is called the weakly dissipative periodic b-family of equations. Under the effect of dissipation, we derive two blow-up criteria to this equation with certain initial data. When the parameters α, λ, and b belong to a suitable range, our present blow-up criteria improve and extend the previous relevant blow-up results.
Boltzmann-based second-order constitutive models of diatomic and polyatomic gases including the vibrational mode
Authors: Mankodi Tapan K. , Myong R. S.
Published: December 2020

Describing diatomic and polyatomic gases at high temperatures requires a deep understanding of the excitation of molecules to a higher vibrational level. We developed new second-order constitutive models for diatomic and polyatomic gases with vibrational degrees of freedom, starting from the modified Boltzmann–Curtiss kinetic equation. The closing-last balanced closure and cumulant expansion of the calortropy production associated with the Boltzmann collision term are key to the derivation of the second-order models, compatible with the second law of thermodynamics. The topology of the constitutive models showed the presence of highly nonlinear and coupled protruding or sunken regions in the compression branch. It was also shown that the vibrational mode reduces the level of nonlinearity in the topology. In addition, analysis of a strong shock structure highlighted the interplay between the second-order effects in the constitutive relations and the vibrational–translational relaxation. Finally, the analysis showed that the results of the second-order models were in better agreement with the direct simulation Monte Carlo data, when compared with the results of the first-order models, especially in the profiles and slopes of density, velocity, and vibrational temperatures.
Anisotropic and trap-limited diffusion of hydrogen/deuterium in monoclinic gallium oxide single crystals
Authors: Reinertsen Vilde M. , Weiser Philip M. , Frodason Ymir K. , Bathen Marianne E. , Vines Lasse , Johansen Klaus Magnus
Published: December 2020

The effect of lattice anisotropy on the diffusion of hydrogen (H)/deuterium (2H) in β-Ga2O3 was investigated using secondary ion mass spectrometry (SIMS) and hybrid-functional calculations. Concentration-depth profiles of 2H-implanted single crystals show that 2H can diffuse along the direction perpendicular to the (010) surface at temperatures as low as 300 °C, whereas diffusion along the direction perpendicular to the (-201) surface occurs only around 500 °C. For both directions, the evolution of the 2H concentration–depth profiles after heat treatments can be modeled by trap-limited diffusion. Moreover, the traps can be present in the as-received crystals or created during ion implantation. Comparison of the experimentally obtained binding energy for 2H to the trap (2.3 ± 0.2 eV) with the binding energies determined from first-principles calculations suggests that intrinsic point defects (e.g., VGaib) or defect complexes (e.g., VGa(2)VO(2)) are excellent candidates for the trap and will play a crucial role in the diffusion of H or 2H in β-Ga2O3.
Quantification of the flame structure at multi-scale levels
Authors: Tan G. , Ahmed U. , Wang L. , Chakraborty N.
Published: December 2020

The interaction between flame and turbulence leads to the complex flame topology at multiple scales. In this work, the non-local statistical features of the flame surface topology in turbulent premixed combustion are investigated by using the dissipation element (DE) analysis. Considering a spatial point on the flame front, the gradient trajectory of the flame curvature reaches a local maximum curvature point and a local minimum curvature point along the ascending and descending directions, respectively. A DE is the patch consisting of the points whose gradient trajectories share the same pair of extremal points. The characteristic parameters are chosen as the distance and the curvature difference between two extremal points of each DE. Multi-scale DEs can also be defined to improve the understanding of the turbulent premixed flame surface topology at various scales by extending the extremal points at different scale levels. The results show that the turbulence intensity determines the flame corrugation and consequently the number of DEs, whereas the probability density functions of the normalized length scale of DEs remain unchanged. The conditional mean of the curvature difference with respect to the length scale is strongly dependent on the influence of turbulence on the flame, i.e., that scaling slope decreases with an increase in the turbulence intensity. However, for a given turbulence intensity, the scaling slopes of such conditional mean remain unchanged in different scale brackets.
Measuring the shock Hugoniot data of liquid nitrogen using a cryogenic system for shock compression
Authors: Sabeeh Akram M. , Fan Zhuo-Ning , Zhang Ming-Jian , Liu Qi-Jun , Liu Fu-Sheng
Published: December 2020

The study of homonuclear diatomic molecules under high pressure and high temperature is a fundamental problem of condensed matter physics. In this research work, a cryogenic target (CT) was built to liquefy the gas and execute shock compression. The characteristics of the CT and the diagnostic system are explained in detail. We performed a shock compression of liquid nitrogen by using a two-stage light-gas gun at pressures up to 93 GPa (0.93 Mbar). Impactor velocities were measured with the magnetic velocimetry system, with a precision of 0.2%. The optical waveforms were recorded with the Doppler pin system, then further fast Fourier transform obtained velocity profiles in the sample. The measured velocity profiles were used to identify optical reflectance and obtain first-shock velocities, independent of the sample thickness above dissociative pressure (>30 GPa). The measured shock velocities had an uncertainty of less than 1%. First particle velocities were calculated by impedance matching, and the second velocities were directly calculated from the velocity profiles in an LiF anvil. The experimental shock Hugoniot results were observed to be consistent with those of the previous work. However, the principal Hugoniot softened above 27 GPa, and the uncertainties in the first and second-shock volumes were less than 0.7% and 3%, respectively.
Intrinsic water layering next to soft, solid, hydrophobic, and hydrophilic substrates
Authors: Chen Meng , Li Lin , Zhu Runliang , Zhu Jianxi , He Hongping
Published: December 2020

How a substrate modulates properties of water upon it and how far the perturbation is present remain to be fundamental questions in surface science. To answer these questions, we develop a layer-by-layer exfoliation method to identify physically meaningful water layers upon a substrate through molecular dynamics simulations under ambient conditions. The results show a qualitatively consistent long-ranged layer-by-layer propagation of the atomic structure, irrespective of whether the substrate is soft, solid, hydrophobic, or hydrophilic. The capillary-wave fluctuation of a water layer upon air or oil diverges with long wavelength but is truncated upon solid substrates by an effective field, which exhibits a long-ranged decay but its strength is almost irrelevant with substrate chemistry. The distinction in the water structure and atomic dynamics due to substrate specificity is mostly limited to the outmost layer. We conclude a long-ranged layering organization and a short-ranged substrate-dependent specificity for interfacial water.
Revealing a metastable cubic phase in CoFe2O4–SrTiO3 three-dimensional network heteroepitaxial nanostructure
Authors: Song Haili , Li Chao , Wang Chih-Kuo , Yang Jan-Chi , Lin Jianjun , Sun Lin , Cheng Yan , Qi Ruijuan , Zhang Yuanyuan , Huang Rong , Chu Ying-Hao , Duan Chun-Gang
Published: December 2020

CoFe2O4–SrTiO3 nanostructured thin films grown on a SrTiO3 (001) substrate are typical self-assembled vertical heteroepitaxial nanocomposites (VHNs) with CoFe2O4 nanopillars embedded into a SrTiO3 matrix. When the film thickness increased from ∼20 nm to ∼80 nm, a new three-dimensional network heteroepitaxial nanostructure in which a SrTiO3 core surrounded by a CoFe2O4 rhombus boundary was created. A new metastable CoFe1.48O3.22 cubic structure formed between the CoFe2O4 and SrTiO3 matrix/substrate as a result of the local strain field at a CoFe2O4/SrTiO3 interface forcing a part of tetrahedral Fe cations in CoFe2O4 to diffuse into the adjacent SrTiO3. Compared with the VHN structure, the new three-dimensional network heteroepitaxial nanostructure enhanced the perpendicular magnetic anisotropy mainly due to the shape anisotropy.
Length measurement of single-walled carbon nanotubes from translational diffusion and intensity fluctuations
Authors: Lee Antony , Cognet Laurent
Published: December 2020

A new approach is presented to measure the length distribution of dispersed single-walled carbon nanotubes (SWCNT). In this method, the diffusive trajectories of individual SWCNTs in solution are reconstructed from high frame rate video stacks. These trajectories allow the estimation of two key statistics for the SWCNTs: their translational diffusion coefficient and the autocorrelation time of their fluorescence intensity. We show that the autocorrelation time is a measure of the rotational diffusion coefficient of the SWCNTs and that the length of the SWCNTs can be estimated either from the rotational diffusion coefficients alone or by combining translational and rotational diffusion coefficients. Moreover, this last estimate does not require knowledge of the solution viscosity or of the SWCNT hydrodynamic diameter.
Compression ramp shock wave/boundary layer interaction control with high-frequency streamwise pulsed spark discharge array
Authors: Tang Mengxiao , Wu Yun , Guo Shanguang , Liang Hua , Luo Yanhao
Published: December 2020

A streamwise array of pulsed spark discharge operating at a high frequency of 10 kHz is used to control the shock wave/boundary layer interaction (SWBLI) induced by a 24° compression ramp (CR) in a Mach 2.0 flow. High-speed schlieren imaging at 50 000 frames/s is deployed for flow visualization. The schlieren snapshots, as well as statistics of the schlieren sequence, show that the intensity weakening effect on the shock wave can be achieved for a long time up to 20 ms, which is the first experimental demonstration of stable control on the CR-SWBLI with plasma actuators. Then, based on fast Fourier transform analyses, the low-frequency unsteadiness of the shock wave is also significantly modified and the dominant oscillation frequency is switched to the high frequency St = 0.32. The mechanism of the encouraging control outcome is finally discussed that the strong separation wave induced by a CR is replaced by a multistage weak compression wave produced through a high-frequency actuator array.
Asymmetric splash and breakup of drops impacting on cylindrical superhydrophobic surfaces
Authors: Zhang Haixiang , Zhang Xiwen , Yi Xian , He Feng , Niu Fenglei , Hao Pengfei
Published: December 2020

Drop splash and breakup on cylindrical surfaces play an important role in a wide variety of industrial applications. In this work, water drops with a wide range of impact velocities (1.4 m/s–4.5 m/s) and cylindrical stainless steels with different diameters (1 mm–20 mm) are employed to investigate the asymmetric splash and breakup characteristics of drops impacting on cylindrical superhydrophobic surfaces. We identify two interesting phenomena, asymmetric splash and converging breakup. The splash behavior is found to be asymmetric in different directions, and the drops preferentially splash in the axial direction. Fundamentally, we propose two disparate splash thresholds, referring to the Weber number We and the diameter ratio D* = D/D0, in the azimuthal and axial directions, respectively. The converging breakup is caused by the much more rapid converging of the liquid rim in the axial direction than in the azimuthal direction. The aspect ratio βzmax/βxmax, governing the converging breakup, increases with We and decreases with D*. Fortuitously, the splashing angle θ is demonstrated to only depend on D* rather than We, and the relational expression of θ and D* is provided. Ultimately, we put forward universal relations between the mean diameter and velocity of secondary droplets, resulting from the converging breakup, and the dimensionless parameter We/D*. The results of this work are expected to provide valuable insights into anti-icing and microfluidics fields.
Optical microprism cavities based on dislocation-free GaN
Authors: Hjort Filip , Khalilian Maryam , Bengtsson Jörgen , Bengths Marcus , Gustavsson Johan , Gustafsson Anders , Samuelson Lars , Haglund Åsa
Published: December 2020

Three-dimensional growth of nanostructures can be used to reduce the threading dislocation density that degrades III-nitride laser performance. Here, nanowire-based hexagonal GaN microprisms with flat top and bottom c-facets are embedded between two dielectric distributed Bragg reflectors to create dislocation-free vertical optical cavities. The cavities are electron beam pumped, and the quality (Q) factor is deduced from the cavity-filtered yellow luminescence. The Q factor is ∼500 for a 1000 nm wide prism cavity and only ∼60 for a 600 nm wide cavity, showing the strong decrease in Q factor when diffraction losses become dominant. Measured Q factors are in good agreement with those obtained from quasi-3D finite element frequency-domain method and 3D beam propagation method simulations. Simulations further predict that a prism cavity with a 1000 nm width will have a Q factor of around 2000 in the blue spectral regime, which would be the target regime for real devices. These results demonstrate the potential of GaN prisms as a scalable platform for realizing small footprint lasers with low threshold currents.
Splashing of liquid droplet on a vibrating substrate
Authors: Khabakhpasheva T. I. , Korobkin A. A.
Published: December 2020

The unsteady axisymmetric problem of a liquid drop impacting onto a rigid vibrating substrate is studied. Initially, the drop is spherical and touches the flat substrate at a single point. Then, the substrate starts to move toward the drop and vibrate with a small amplitude and high frequency. The early stage of the impact is studied by using the potential flow theory and the Wagner approach in dimensionless variables. The effect of the substrate vibration on the drop impact is described by a single parameter. It is shown that the vibration of the substrate leads to oscillations of the pressure in the contact region. The low-pressure zone periodically appears in the wetted part of the substrate. The low-pressure zone can approach the contact line, which may lead to ventilation with separation of the liquid from the substrate. The magnitude of the low pressure grows in time. The acceleration of the contact line oscillates with time, leading to splashing of the droplet with the local increase of the thickness of the spray jet sheet at a distance from the contact line. The phase shift of the substrate vibration with respect to the impact instant is not studied. Splashing can be produced only by a forced vibration of the substrate. The impact onto an elastically supported rigid plate does not produce splashing. The obtained results and the theoretical model of the initial stage of drop impact are valid for certain ranges of parameters of the problem.
Spin–orbit torque driven four-state switching in splicing structure
Authors: Song Yuhang , Zhao Xiaotian , Liu Wei , Liu Long , Li Shangkun , Zhang Zhidong
Published: December 2020

We prepared a splicing structure by using electron beam lithography, in which Pt and Ta were spliced together as the spin source upon perpendicularly magnetized Pt/Co/Pt heterostructures. It is found that Pt and Ta can modulate both spin–orbit torque and Dzyaloshinskii–Moriya interaction on the same magnetic layer, respectively. The four-state magnetization switching is achieved with the combinations of two spliced parts, which is observed by using a magneto-optical Kerr microscope. The initial nucleation position determines the chirality. The Pt side stabilizes a right-hand Néel domain wall and the Ta side stabilizes a left-hand Néel domain wall. Our study provides a method for further increasing the storage density and studying spin–orbit torque laterally.
The relationship between the subtropical ridge and Australian temperatures
Authors: Pepler Acacia , Ashcroft Linden , Trewin Blair
Published: December 2020

The intensity and latitude of the subtropical ridge over eastern Australia is strongly associated with southeast Australian rainfall, particularly during the cool months of the year. We show that the subtropical ridge also exerts a strong influence on temperatures across much of Australia, with warmer daytime temperatures and more warm extremes across southern Australia when the subtropical ridge is stronger than average, which is largely independent of the relationship between the subtropical ridge and rainfall. A strong subtropical ridge is also linked to warmer than average minimum temperatures over southern Australia throughout much of the year, except from May to August when a strong ridge is associated with cooler mean minimum temperatures and an increased frequency of cool nights. This relationship, and the observed strengthening of the subtropical ridge during autumn and winter in recent decades, can partially explain the weaker warming trends in minimum temperatures in southeast Australia compared to elsewhere in the country over the period 1960-2016.
Quantifying merging fire behaviour phenomena using unmanned aerial vehicle technology
Authors: Filkov Alexander , Cirulis Brett , Penman Trent
Published: December 2020

Catastrophic wildfires are often a result of dynamic fire behaviours. They can cause rapid escalation of fire behaviour, increasing the danger to ground-based emergency personnel. To date, few studies have characterised merging fire behaviours outside the laboratory. The aim of this study was to develop a simple, fast and accurate method to track fire front propagation using emerging technologies to quantify merging fire behaviour at the field scale. Medium-scale field experiments were conducted during April 2019 on harvested wheat fields in western Victoria, Australia. An unmanned aerial vehicle was used to capture high-definition video imagery of fire propagation. Twenty-one junction and five inward parallel fire fronts were identified during the experiments. The rate of spread (ROS) of junction fire fronts was found to be at least 60% higher than head fire fronts. Thirty-eight per cent of junction fire fronts had increased ROS at the final stage of the merging process. Furthermore, the angle between two junction fire fronts did not change significantly in time for initial angles of 4–14°. All these results contrast with previous published work. Further investigation is required to explain the results as the relationship between fuel load, wind speed and scale is not known.
Base of fresh water, groundwater salinity, and well distribution across California
Authors: Kang Mary , Perrone Debra , Wang Ziming , Jasechko Scott , Rohde Melissa M.
Published: December 2020

Significance

To sustainably manage groundwater, water managers and regulators currently rely upon understanding the depths at which groundwater transitions from fresh (shallower) to more saline (deeper). This base of fresh water, while important, remains poorly understood. Here we show that, in California, 1) available base-of-fresh-water data do not represent actual base of fresh water, as exemplified by the widespread occurrence of fresh water deeper than the defined bases of fresh water, and 2) wells are already penetrating or encroaching on the defined bases of fresh water. We conclude that using current base-of-fresh-water data may limit efforts to manage deep groundwater effectively.
A case study of one teacher’s introduction to task-based language teaching
Authors: Ariatna  , Ellis Rod
Published: December 2020

This article reports a practitioner research study where one of the authors worked with an Indonesian secondary school
teacher to help her introduce task-based language teaching into her own classroom. We report a study involving classroom observation,
interviews, and a reflective journal and show that the teacher was able to develop a good understanding of TBLT principles, construct
well-structured lessons around tasks, and, in the main, to implement TBLT effectively. We also found that there was also a generally
positive response to TBLT from the students and pre- and post- tests provided evidence of language learning. However, we also observed that
while the teacher was able to adopt the role of facilitator, she still sometimes continued to behave as a traditional instructor, dominating
the interactions through display questions and nominating students. We conducted this case study as part of our work as teacher educators
and conclude with a list of the insights we gained can inform professional development programmes for TBLT in Indonesia.
Computer-mediated instruction using ondoku practice for developing elementary school students’ pronunciation
skills
Authors: Wong Steven , Shintani Natsuko
Published: December 2020

This article reports on an elementary school teacher’s research project that evaluated a new teaching practice for
Japanese elementary school students. The project was conducted in two fifth-grade classes comprising a total of 59 students. The
teacher-researcher designed a computer-mediated instructional activity consisting of four-steps called ondoku, which
engaged individual students in reading a given story aloud. It involved the students (a) studying a model reading-aloud video, (b)
video-recording their own reading-aloud performance, (c) receiving teacher corrective feedback on their pronunciation and (d) studying the
feedback and recording and then submitting a second performance. All the steps were carried out in sequence using individual iPads. The
teacher also administered a questionnaire to examine students’ engagement in and perspectives regarding the activity. Analysis involved
comparing the pronunciation in the first and second corrected video files. The results showed that feedback led to successful repair 62
times out of the 108 corrections. In 16 instances, the students were aware of the error and attempted repair but still produced an incorrect
utterance. In 30 instances, the students made no repair. Reflecting on the results and the students’ responses to the questionnaire, the
teacher proposed some changes to the activity.
‘What does the fox say?’
Authors: Hong Seongeun , Kellogg David
Published: December 2020

The late M. A. K. Halliday sketched a language-based theory of learning which posited three overlapping functions of learning language, learning through language, and finally learning about language as the young learner struggles to direct his or her own learning from language. Here we focus on one aspect of this struggle for what Vygotsky called conscious awareness and mastery of learning, namely questions. First we examine Hasan’s case that learning particular kinds of questions enable participation in classroom discourse while others disable it. Next, we look at Vygotsky’s case that self-directed questions (rhetorical and narrativized questions) have a key role to play in learning through questions. Finally, we consider what path the child has to take in learning about questions in English as a foreign language. Using ordinary classroom tasks under ordinary classroom conditions, we trace changes in children’s questions over six months, and we find statistically significant changes, particularly remarkable in retelling dialogues containing questions as narratives. But we also find very few new wh-questions, and we suggest that this is because mastery and conscious awareness of the structure of wh-questions still lie in the next, or proximal, zone of the children’s development.
Implementing task-based language education in primary education
Authors: Van den Branden Kris , Van Gorp Koen
Published: December 2020

This article provides a critical analysis of the language policy measures that were taken by the Flemish government
(Belgium) to improve the quality of the teaching of the national language (Dutch) in compulsory education in Flanders and in the Flemish
education system in Brussels. It builds on Van den Branden (2006a), which documented the
implementation of task-based language teaching (TBLT) in primary, secondary and adult education in Flanders in the period between 1995 and
2005. Focusing on primary education, this article examines the different periods and trends in the government’s attempts to push the
innovation of Dutch language education, and analyses its impact on the practice of teaching the language of schooling. The article
highlights the gradual shift in focus from introducing TBLT materials and supporting the individual teacher to mandating the design of a
school-wide language policy involving the whole school team, and from a top-down implementation to a more bottom-up driven, collaborative
innovation process. The major aim of the article is to identify the factors that impacted on the effects of the innovation policy, against
the backdrop of the growing influx of pupils who do not acquire Dutch (the main medium of instruction) as their mother tongue.
So-adj-a construction as a case of obsolescence in progress
Authors: Rudnicka Karolina
Published: December 2020

The main focus of this study is the so-adj-a construction seen as an instantiation of grammatical obsolescence in progress. Starting at where Klégr’s (2010) synchronic study of the construction’s local grammar and syntactic functions leaves it, the present work provides a diachronic account of changes in the frequency of use in the last two centuries; their implications; and an overview of possible causes that had led to the situation in which the construction became considerably rare in Present Day English. Methodologically, the paper features quantitative and statistical analyses of corpus data. The work uses the framework for the investigation of grammatical obsolescence designed in the author’s doctoral thesis (Rudnicka 2019). Additionally, the present chapter suggests extravagance as a cognitive motivation behind the emergence of the so-adj-a construction.
Captivating, splendid or instructive?
Authors: Boot Peter , Koolen Marijn
Published: December 2020

What is the impact of reading fiction? We analyze online Dutch book reviews to detect overall affective impact, narrative feelings, response to style and reflection. We create a set of rules that analyze the reviews and detect the impact aspects. We evaluate the detection by asking raters about the presence of these aspects in reviews and comparing these ratings to our detection. Interrater agreements are weak to moderate; however, there is a significant correlation between the model’s predictions for all impact aspects except reflection. The detected impact correlates with book genres in the way one would expect: Narrative feelings are highest for thrillers, and stylistic response is highest for literary books. We can thus estimate some aspects of the response books evoke in readers. Initial results suggest that the appreciation of style is linked to reflection in the reader. However, the concepts underlying the impact categories need further exploration.
Synergy of experiment and model for reactive HiPIMS: effect of discharge parameters on WOx composition and deposition rate
Authors: Rezek J , Kozák T , Kumar N , Haviar S
Published: December 2020

Reactive high-power impulse magnetron sputtering of tungsten oxide films using metallic tungsten target (72 mm in diameter) in argon-oxygen atmosphere (total pressure of 0.75 Pa) was carried out. The effect of various discharge parameters on the deposition rate and film oxygen concentration was investigated. Moreover, a model combining a reactive high-power impulse magnetron sputtering model and a discharge plasma model for the ionization region was successfully used for deeper insight into the effect of particular discharge parameters such as voltage pulse length (from 100 –800 µs), oxygen partial pressure (from 0.25–0.50 Pa) or the value of pulse-averaged target power density (from 2.5–500 W cm−2). The results of the presented model, most notably trends in the target- and substrate oxide fraction, composition of particle fluxes onto the substrate, degree of W atom ionization or degree of O2 molecule dissociation are discussed and put into context with experimentally measured quantities.
Enhanced and tunable double Fano resonances in plasmonic metasurfaces with nanoring dimers
Authors: Du Mengyuan , Shen Zhe
Published: December 2020

The appearance of the double-resonance substrate has promoted the application of surface-enhanced Raman scattering (SERS). By controlling the frequencies of the double resonances to match the excitation and Raman scattering frequencies, the detection of the object to be measured can be more effective. For the double-resonance substrate, while the resonance frequencies can be highly controllable, the electric field enhancement is also one of the important factors affecting the application in SERS. In this paper, we designed a metasurface composed of a nanoring dimer array, silica dielectric and gold film. The nanoring dimer array and gold film are separated by the silica dielectric to form a resonant cavity. The localized surface plasmon resonance generated in the nanoring dimer array is coupled with the cavity mode of the resonant cavity. Double Fano resonance with strong electric field enhancement is generated at the gap of the nanoring dimer. The electric field enhancement value can reach 100, which is an order of magnitude larger than that of the nanoring metasurface without the gap structure. The double Fano resonance peaks can be flexibly adjusted while maintaining large electric field enhancements by changing the following parameters: the period of the nanoring dimer array along the direction of the short axis, the ratio of the inner and outer radius of the nanoring and the length of the resonant cavity. Therefore, the proposed metasurface-enhanced Raman scattering substrate provides both the enhanced and tunable double Fano resonances necessary for high-sensitivity, high-selectivity and high-throughput detection. In addition, we proved that the length of the cavity can be determined by theoretical calculation, which avoids a lot of simulation processes.
Autofocusing based on cosine similarity in dual-wavelength digital holographic microscopy
Authors: Yu Hongqiang , Jia Shuhai , Liu Yuba , Peng Jun , Zhou Xing , Yang Shuming
Published: December 2020

An autofocusing method based on cosine similarity in dual-wavelength digital holographic microscopy is proposed. In our experiments, red and green lasers are employed for illumination and the generated holograms are recorded by a color camera. During the refocusing process, the reconstructed optical field near the focus plane contains more regular features than the one on the defocus plane. Moreover, due to the wavelength dependency of the diffraction process, the further away from the focus plane, the greater the difference in the reconstructed optical fields from the two wavelengths. Therefore, the focus plane can be determined by finding the maximum value of the cosine similarity between the amplitude vectors from the reconstructed optical fields of the two wavelengths. Simulation and experimental results demonstrate the effectiveness of the proposed method in off-axis dual-wavelength digital holographic microscopy for shape measurement.
Application of functionalized graphene in Li–O2 batteries
Authors: Cui Xinhang , Luo Yani , Zhou Yin , Dong Wenhao , Chen Wei
Published: December 2020

Li–O2 batteries (LOB) are considered as one of the most promising energy storage devices using renewable electricity to power electric vehicles because of its exceptionally high energy density. Carbon materials have been widely employed in LOB for its light weight and facile availability. In particular, graphene is a suitable candidate due to its unique two-dimensional structure, high conductivities, large specific surface areas, and good stability at high charge potential. However, the intrinsic catalytic activity of graphene is insufficient for the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in LOB. Therefore, various surface functionalization schemes for graphene have been developed to tailor the surface chemistry of graphene. In this review, the properties and performances of functionalized graphene cathodes are discussed from theoretical and experimental aspects, including heteroatomic doping, oxygen functional group modifications, and catalyst decoration. Heteroatomic doping breaks electric neutrality of sp2 carbon of graphene, which forms electron-deficient or electron-rich sites. Oxygen functional groups mainly create defective edges on graphene oxides with C−O, C=O, and −COO−. Catalyst decoration is widely attempted by various transition and precious metal and metal oxides. These induced reactive sites usually improve the ORR and/or OER in LOB by manipulating the adsorption energies of O2, LiO2, Li2O2, and promoting electron transportation of cathode. In addition, functionalized graphene is used in anode and separators to prevent shuttle effect of redox mediators and suppress growth of Li dendrite.
EMC3-EIRENE modelling of tungsten behavior under resonant magnetic perturbations on EAST: Effects of tungsten sputtering and impurity screening
Authors: Dai S Y , Zhang H M , Lyu B , Sun Y W , Jia M N , Feng Y , Wang Z X , Wang D Z
Published: December 2020

The studies on tungsten (W) sputtering and transport characteristics on EAST tokamak under resonant magnetic perturbation (RMP) fields have been performed with the three-dimensional edge transport code EMC3-EIRENE. The estimation of the W sputtering flux has been carried out based on EMC3-EIRENE modeling for RMP and no RMP applications. The W sputtering flux shows a small difference between RMP and no RMP cases due to weak sensitivity of W sputtering yield on deuterium impact energy for low edge plasma density. However, for high edge plasma density, the strong dependence of W sputtering yield on deuterium impact energy comes into play, which results in a remarkable difference in the W sputtering flux between RMP and no RMP cases. Impacts of the W impurity perpendicular transport on W ions transport have been investigated. With low W perpendicular transport coefficient for RMP case, the edge plasma has a better W ions screening effect for high edge plasma density. The increased W perpendicular transport coefficient results in a good W ions screening effect for both high and low edge plasma densities.
Direct growth of tungsten disulfide on gallium nitride and the photovoltaic characteristics of the heterojunctions
Authors: Wen Yu , Debbarma Rousan , Rasul Md Golam , Shahbazian-Yassar Reza , Berry Vikas , Shi Junxia
Published: December 2020

Photovoltaic device construct with a 2D nanomaterial atop a 3D wide bandgap semiconductor enables van Hove singularity induced enhanced light absorption on the front surface in close proximity (few atoms above) to the depletion region. Here, thin layers of tungsten disulfide (WS2) varying from mono to few layers were grown directly on both n-gallium nitride (GaN) and p-GaN via low pressure chemical vapor deposition. The conditions for WS2 growth were optimized for a larger coverage of the GaN substrate. The WS2 film was characterized using confocal Raman spectroscopy and x-ray photoelectron spectroscopy. Ultraviolet photoelectron spectroscopy measurement was conducted to elucidate the electronic band structures of WS2 on top of GaN. Afterwards, WS2/GaN heterojunction photovoltaic devices were fabricated. The current density–voltage (J–V) tests were conducted to illustrate the electrical performance. The device showed an open circuit voltage of 0.53 mV and a short circuit current density of 60 µA cm−2, 85% higher than that of a WS2/Si solar cell. An external quantum efficiency was measured to be near 60% for red and infrared, and above 50% in the violet region.
An inclined MHD mixed radiative-convection flow of a micropolar hybrid nanofluid within a lid-driven inclined odd-shaped cavity
Authors: Mansour M A , Mahdy A , Ahmed S E
Published: December 2020

The present article scrutinizes the impact of partial slip on mixed-radiative interaction convection flow of a non-Newtonian micropolar hybrid nanofluid with an inclined magnetic field in an odd-shaped porous cavity due to separated heating. Partial slip influence is assumed to be along an inclined walls af and ef. A source of constant heat flux on the walls bc and cd is implemented. Besides, the two walls ab and de are kept to be at low temperature T

c
. The other lid-driven porous cavity walls are selected to be adiabatic. The flow controlling equations are solved implementing the finite difference technique and the numerical computations are confirmed with earlier published papers successfully. Features of the temperature, streamlines and angular velocity as well Nusselt number are provided and argued for miscellaneous cases. The alteration of the vortex parameter enhances values of the angular velocity while the stream lines did not show any changes. An enhancement in values of the local Nusselt number is demonstrated as the geometry inclination angle is growing, while variations of lengths and locations of the active boundaries have negative impacts on the local Nusselt number. The outcomes show that, at a certain values of Darcy number (Da = 0.01), there is an improvement in average Nusselt number up to 9.9% when the nanoparticle parameter varied from 0 (pure) to 10%.
Subwavelength three-dimensional Rydberg atom localization by optical absorption microscopy
Authors: Zhang Hengfei , Yuan Jinpeng , Wu Chaohua , Wang Lirong , Xiao Liantuan , Jia Suotang
Published: December 2020

We propose a scheme for subwavelength three-dimensional (3D) Rydberg atom localization in a (V + Ξ)-type atomic system by spatial optical absorption microscopy. Position-dependent atom–field interaction allows atom position information to be obtained via measurement of the probe absorption. Some distinctive spatial localization patterns are discovered by adjusting the detuning and Rabi frequency of the laser fields. A 100% probability of finding the Rydberg atom at a specific position in 3D subwavelength space is achieved under appropriate conditions. This scheme may provide a novel approach for realizing high-precision 3D Rydberg atom localization in experiment.
Study of the CKM angle γ sensitivity using flavor untagged

decays *
Authors: Ao D. , Decamp D. , Qian W. B. , Ricciardi S. , Sazak H. , T’Jampens S. , Tisserand V. , Wang Z. R. , Yang Z. W. , Zhang S. N. , Zhou X. K.
Published: December 2020

A sensitivity study on the measurement of the CKM angle

from

decays is conducted using the D-meson reconstructed in the quasi flavour-specific modes

,

, and

, as well as CP-eigenstate modes

and

, where the notation

corresponds to a

or

meson. The LHCb experiment is presented as a use case. A statistical uncertainty of approximately

can be achieved with the

collision data collected in the LHCb experiment from 2011 to 2018. The sensitivity to

should be of the order

after accumulating 23 fb-1 of

collision data by 2025, whereas it is expected to improve further by 300 fb-1 by the second half of the 2030 decade. The accuracy is dependent on the strong parameters

and

, which together with

describe the interference between the leading amplitudes of the

decays.
On the influence of inlet perturbations on slug dynamics in horizontal multiphase flow—a computational study
Authors: Schmelter S , Knotek S , Olbrich M , Fiebach A , Bär M
Published: December 2020

When multiphase flows are modeled numerically, complex geometrical and operational features of the experiments, such as the phase mixing section, are often not resolved in detail. Rather simplified boundary conditions are prescribed, which usually cause less irregular dynamics in the system than present in reality. In this paper, a perturbation that randomly disturbs the secondary components of the velocity vector at the inlet is proposed in order to capture the experimentally observed instabilities at the interface between the phases. This in particular enhances the formation of slugs in the pipe. Different amplitudes of the perturbation are investigated. One observes that, the higher the perturbation amplitude, the earlier the slugs occur. On the other hand, sufficiently far away from the inlet, the flow pattern shows the same dynamics for different perturbation amplitudes. Hence, no specific frequency is imposed by the prescribed perturbation. The simulation results are validated by comparison with liquid level data from a corresponding experiment.
Numerical investigation of the tritium permeation phenomenon through cooling plates in breeding blankets
Authors: Urgorri F.R. , Moreno C. , Rapisarda D.
Published: December 2020

Understanding and predicting tritium transport is considered a key issue for the design of safe and self-sufficient fusion power plants. Indeed, tritium generated in the breeder materials is susceptible to permeate to the blanket coolant circuits where it is harder to remove and process. Therefore, the predictive models become very important to evaluate the performance of any blanket design. In this work, 2D finite volume methods are employed to analyze in detail the tritium permeation through a cooling plate considering a set of different parameters that affect the breeding blanket (BB) performance. Different BB configurations are studied varying the geometrical parameters defining the plate: the wall thickness and the cooling channel pitch. Moreover, the analyses cover every permeation regime, from diffusion-limited to surface-limited, including intermediate situations. This way, results are applicable to every BB concept which employs cooling plates with independence of their specific materials, temperatures and tritium concentrations. Results have been compared with those of 1D models in order to define form factors that can be used to increase the precision of system level tritium transport models. A total of 91 simulations have been carried out to find correlations that allows computing the form factors in a wide variety of situations. Results show that the accuracy of 1D models and consequently the accuracy of most system level models strongly depends on the permeation regime and can be poor in some conditions. However, this study demonstrates that the use of form factors can be used for an effective increase of system level exactness.
Soil moisture seasonality alters vegetation response to drought in the Mongolian Plateau
Authors: Lu Zihan , Peng Shushi , Slette Ingrid , Cheng Guoquan , Li Xiran , Chen Anping
Published: December 2020

The Mongolian Plateau (MP) experienced the most severe decadal drought of the past two millennia from 2000 to 2009 and several shorter-term droughts in the 2010s. Using satellite-based near-infrared reflectance of vegetation (

NI

R

V

), we examined changes in vegetation productivity of the MP from 2000 to 2018. During this time, soil moisture in March (

S

M

Mar

) mainly determined spring

NI

R

V

, and early-summer (June and July) precipitation mainly determined summer

NI

R

V

.

Our study revealed three distinct periods: the severely dry period of 2000–2009, recovery in 2010–2012, and a relatively stable period with occasional short-term droughts after 2012. While vegetation productivity experienced a significant decrease during the severe decadal drought, summer and spring productivity quickly recovered after 2010, following an increase in growing season (GS) rainfall and winter snowfall. Greater

S

M

Mar

, which resulted from previous GS precipitation, contributed to smaller declines in vegetation productivity during the short-term droughts in 2014, 2015 and 2017. The decline in vegetation productivity during the severe decadal drought damaged livestock operations in Mongolia, but had a limited effect on operations in Inner Mongolia of China, where human intervention is stronger. Given evidence that drought impacts are increasing worldwide, it is important to understand the factors determining ecosystem drought responses. Many drought studies have focused on GS precipitation, but our results show that pre-GS SM can play an important role in determining drought impacts. Our results also demonstrate that strong interventions will be needed in order to sustain livestock operations during intensifying drought.
Phase transition in random noncommutative geometries
Authors: Khalkhali Masoud , Pagliaroli Nathan
Published: December 2020

We present an analytic proof of the existence of phase transition in the largeNlimit of certain random noncommutative geometries. These geometries can be expressed as ensembles of Dirac operators. When they reduce to single matrix ensembles, one can apply the Coulomb gas method to find the empirical spectral distribution. We elaborate on the nature of the largeNspectral distribution of the Dirac operator itself. Furthermore, we show that these models exhibit both a single and double cut region for certain values of the order parameter and find the exact value where the transition occurs.
Extracting the local electronic states of Pt polycrystalline films surface under electrochemical conditions using polarization-dependent total reflection fluorescence x-ray absorption near edge structure spectroscopy
Authors: Wakisaka Yuki , Uehara Hiromitsu , Yuan Qiuyi , Kido Daiki , Wada Takahiro , Uo Motohiro , Uemura Yohei , Yokoyama Toshihiko , Kamei Yutaro , Kuroda Seiichi , Ohira Akihiro , Takakusagi Satoru , Asakura Kiyotaka
Published: December 2020

The local atomic information about the interface between the 30 nm-thick Pt polycrystalline films and the solution with and without perfluorosulfonic acid polymers (Nafion®) for the model cathode catalyst of fuel cell has been captured under electrochemical conditions using polarization-dependent total reflection fluorescence x-ray absorption near edge structure spectroscopy (PTRF–XANES). The results show that the formation of sub-monolayer-equivalent PtO or adsorbed hydrogen/oxygen species in the surface region can be successfully observed in the PTRF–XANES spectra when the thickness of the solution layer and the incidence angle are properly controlled. This capability enables us to examine the metal /(Nafion®/) solution interface structure through XANES together with other surface analysis methods, which will enhance comprehensive understanding of the nature of the interface of the fuel cell system.