bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and experiment of a bionic flapping wing mechanism with flapping–twist–swing motion based on a single rotation
Authors: Ji Bing , Zhu Qiaolin , Guo Shijun , Yang Fan , Li Yushuai , Zhu Zenggang , Chen Si , Song Rui , Li Yibin
Published: June 2020

In the present study, a bionic flapping mechanism of a spatial six-bar configuration was designed to transform a single rotation of a motor into a three degrees of freedom “flapping–twist–swing” cooperative motion of a flapping wing. The kinematics model of the flapping mechanism movement was constructed. The flapping trajectory of the wing based on the kinematics model was to mimic the motion of a pigeon wing in landing flight. To reduce the manufacturing complexity, the flapping mechanism was simplified with only two degrees of freedom (flapping and twist) retained. Finally, a prototype model with a 0.9 m wing span was built and tested. A comparison among the experimental data, theoretical calculation results, and ADAMS simulation results revealed that the difference in the flapping and the twist amplitude between experimental observations and theoretical calculation results was 12.5% and 2.3%, respectively. This was owing to the elastic deformation of the bar and the mechanism simplification. The comparison results also indicated that the maximum difference in the inertial force was 5.9% in up-stroke and 6.7% in down-stroke, respectively. The experimental results showed that the inertial force of the model with the wing patagium was approximately 2.2 N, and the maximum positive and negative lift was 2.1 N and −1.5 N, respectively. It is hoped that this study can provide guidance for the design of bionic flapping wing mechanisms of a flapping wing aircraft for short landing flight.
Heat transfer suppression by suspended droplets on microstructured surfaces
Authors: Wei Mengyao , Song Youngsup , Zhu Yangying , Preston Daniel J. , Tan Chuan Seng , Wang Evelyn N.
Published: June 2020

Manipulating the degree of droplet contact with a surface significantly impacts applications involving drag reduction, corrosion inhibition, droplet transportation, and thermal management. Extensive studies have been conducted to study droplet wetting behavior on plain and micro/nanostructured surfaces, with a particular focus in the recent literature on heated surfaces, where evaporation beneath the droplet impacts the apparent wettability. In previous literature, the peak droplet lifetime and minimum heat transfer on heated surfaces were observed at the Leidenfrost point. In this study, however, we report the existence of two distinct peaks for droplet lifetime on heated surfaces structured with silicon micropillar arrays. Initially, droplets exhibit complete wetting at low surface temperatures, but as surface temperature increases, the wetting state transitions first to a contact non-wetting state (i.e., a Cassie–Baxter-like state) and then to the non-contact Leidenfrost state; two distinct local maxima in droplet lifetime are observed, one corresponding to each transition. The contact non-wetting transition temperature and Leidenfrost point increase with larger micropillar pitch and taller height, which we attribute primarily to the resulting lower effective thermal conductivity of the micropillar array beneath the droplets, in agreement with the analytical force-balance-based modeling. This study provides a comprehensive investigation of the effect of surface structuring on contact non-wetting and Leidenfrost phenomena and will serve as design guidelines in controlling the contact non-wetting and Leidenfrost temperatures for specific applications.
Ion temperature measurement techniques using fast sweeping retarding field analyzer (RFA) in strongly intermittent ASDEX Upgrade tokamak plasmas
Authors: Ochoukov R. , Dreval M. , Bobkov V. , Faugel H. , Herrmann A. , Kammerloher L. , Leitenstern P. ,   ASDEX Upgrade Team,   EUROfusion MST1 Team
Published: June 2020

This manuscript presents a new method of interpreting the ion temperature (Ti) measurement with a retarding field analyzer (RFA) that accounts for the intermittent/turbulent nature of the scrape off layer (SOL) plasmas in tokamaks. Fast measurements and statistical methods are desirable for an adequate description of random fluctuations caused by such intermittent events as edge localized modes (ELMs) and blobs. We use a RFA that can sweep its current–voltage (I–V) characteristics with up to 10 kHz. The RFA uses an electronics compensation stage to subtract the capacitive pickup due to the finite connecting cable capacitance, which greatly improves the signal-to-noise ratio. In the 10 kHz case, a single I–V characteristic is obtained in time, which is an order of magnitude faster than the ELM cycle. The fast sweeping frequency allows us to reconstruct the Ti probability density function (PDF), which we use as the Ti representation. The boundary conditions that we place on the I–V characteristics when calculating the Ti values impact the resulting Ti PDF. If the boundaries are insensitive to the plasma fluctuations, then the most probable Ti value of the PDF (20 eV–25 eV) is similar to the Ti value obtained via the classical conditional averaging method (20 eV–27 eV). However, if the boundary conditions follow the fluctuations, then the PDF-based method gives a substantially higher most probable Ti value (35 eV–60 eV). Overall, we show that a fast sweeping RFA diagnostic should be used in intermittent SOL plasmas to reconstruct the PDF for accurate Ti measurements.
Molecular dynamics studies on spark plasma sintering of Ge–Si based thermoelectric material
Authors: Kuznetsov Yuri , Bastrakova Marina , Dorokhin Mikhail , Erofeeva Irina , Demina Polina , Uskova Elena , Popov Alexander , Boryakov Alexei
Published: June 2020

The development of new fabrication technologies for Ge–Si thermoelectric materials requires a corresponding theoretical description of physical processes lying behind the synthesis. In the present paper, we investigated the interdiffusion of Si and Ge atoms at the Ge/Si interface, which takes place during spark plasma sintering of Ge and Si powders for fabrication of thermoelectric bulk. The calculation was performed using numerical simulation based on the classical molecular dynamics method. The diffusion coefficients of Si in Ge and vice versa were found at sintering temperatures of 900 K–1300 K and an external pressure of 7 MPa. The calculation results were used to analyze the experimental data derived from the measurements of Ge and Si profiles at the interface of thin Ge/Si plates subjected to spark plasma sintering at the temperature of 1160 K (887 °C). The comparison of measured and calculated diffusion profiles has shown good agreement with one another.
Sexual dimorphism in the dioecious monocot Lomandra leucocephala ssp. robusta and its potential ecosystem and conservation significance
Authors: Draper Jenna T. , Conran John G. , Crouch Nicholas , Weinstein Philip , Simpson Bradley S.
Published: June 2020

Dioecious plants constitute 7% of all angiosperm species, yet they occur in many habitat types, partially through the deployment of sexual dimorphisms that assist in reproduction. In the present work, the dioecious monocot Lomandra leucocephala ssp. robusta (Asparagaceae: Lomandroideae) was studied to understand how sexual dimorphisms can assist species conservation and inform us of a species’ potential significance in an ecosystem. Floral display was sexually dimorphic, as male inflorescences were displayed more prominently and more conspicuously in UV range. Male nectar analysed by thin-layer chromatography contained a higher glucose content than female nectar. However, both sexes contained hexose-rich nectar, a common indicator of generalist pollination, which was supported by observations of floral visitors. Floral extract comparison conducted via gas chromatography-mass spectrometry showed that male extracts contained more compounds that potentially convey greater resistance to biotic and abiotic threats. Chemical comparison of leaves by high performance liquid chromatography with peak area ratio analysis revealed this technique could be used as a tool for gender identification of individuals during non-flowering periods. Due to the generalist pollination mechanisms of L. leucocephala ssp. robusta, may have an important role in the conservation and support of local insect populations. The presence of chemical biotic and abiotic resistance may also make L. leucocephala ssp. robusta a significant contributor to the ongoing stabilisation of the sand dunes. Conservation efforts required for L. leucocephala ssp. robusta are likely to be minimal, as pollination services are provided by a diversity of pollinating taxa, including introduced species, which will be abundant regardless of variable flowering periods. Further observational study of L. leucocephala ssp. robusta pollinators and differences in pollinator visitation behaviours between sexes is recommended to better understand efficient pollination for the species, and potentially reveal a greater extent of ecosystem benefit for this species.
How do we support walking prescriptions for type 2 diabetes management? Facilitators and barriers following a 3-month prescription
Authors: Reynolds Andrew N. , Moodie Ian , Venn Bernard , Mann Jim
Published: June 2020

ABSTRACT
INTRODUCTIONPrescribing physical activity is an inexpensive method to promote patients’ long-term health, but determinants of adherence with physical activity prescriptions are seldom considered.
AIMTo identify facilitators and barriers experienced by adults with type 2 diabetes when prescribed regular walking.
METHODSParticipants were prescribed a regular walking routine that met current physical activity guidelines for type 2 diabetes management for a period of 3 months. Pre- and post-intervention questions considered participants’ self-rated health and physical activity amount. Thematic analysis of recorded interviews held after the 3-month prescription identified barriers and facilitators to adherence for participants.
RESULTSTwenty-eight adults (aged 60±9 years, body mass index 32.3±4.0kg/m2, HbA1c 59±16mmol/mol) participated in the 3-month intervention, providing 7 years of lived experience. Self-rated health (14%; 95% confidence interval (CI) 7–22%) and time spent walking (+11 min/day; 95% CI 4–18 min/day) increased following the prescription. Major themes motivating participants were: establishing a walking routine; the support of their family members; observing health benefits; and being monitored by a health professional. The greatest barriers were associated with walking in the evening and included feelings of insecurity in the dark or a preference for sedentary behaviour.
DISCUSSIONA prescription to walk increased time spent in physical activity and self-rated health in adults with type 2 diabetes. Health-care professionals can support walking prescriptions by promoting facilitators and reducing barriers to prescription adherence. Practical solutions to barriers include identifying alternative physical activity opportunities within the house or advice to develop support networks to provide company while walking.
Bacteria, garbage, insects and pigs
Authors: Simonsen Sandra
Published: June 2020

The present paper focuses on the symbolic meanings of metaphors and their potential social effects. Specifically, it examines the case of the Jewish Ultra-Orthodox “Ḥardakim” poster campaign distributed throughout Ultra-Orthodox communities in Israel in 2013. Following social group theory, the paper interprets the symbolic meanings of the main metaphors in the campaign in order to reconstruct the lifeworld of this religious group. On that basis, it offers a discussion of how metaphors were strategically utilized in order to draw social boundaries, uphold social norms and sanction group members who deviate from those. The paper’s empirical contribution is a case study of how symbolic meanings of metaphors as a part of propagandistic discourse targets and exploits social identities in order to mobilize collective emotions thereby provoking certain actions. It contributes theoretically by arguing that deeming norm-deviant group members internal threats is an efficient propaganda tool for maintaining intragroup behavioral codes.
Effects of cobalt on mechanical properties of high silicon ductile irons
Authors: González-Martínez R. , Sertucha J. , Lacaze Jacques
Published: June 2020

High silicon ductile irons are being developed due to their advantages relating to pearlitic-ferritic grades (high ductility, fully ferritic structures, good machinability, etc.). Recent studies reported that silicon contents higher than 5.2 wt-% originates drastic embrittlement due to chemical ordering. For improving the mechanical properties, the addition of other alloying elements becomes an interesting way of work. This study focuses on the cobalt effect on as-cast microstructures and mechanical properties of ductile irons with silicon contents that maximise ultimate tensile strength. The results obtained show that addition of 4 wt-% cobalt increases the ultimate tensile strength by about 10% and decreases the silicon content at the maximum in this property respecting the unalloyed alloys because cobalt enhances ordering as does silicon.
How do you Reconstruct a Historic Private Library? A Methodological Review and Checklist for First-Time Historical-Bibliographic Sleuths
Authors: Penge Edwina
Published: June 2020

Despite the number of studies which set out to reconstruct an individual’s library, critical reviews of the methodology of library reconstruction seem to be lacking within the discourse of library history. So, the question arises, ‘How do you reconstruct a historic, private library?’ This article examines the practical ‘how to’ of library reconstruction with a view to offering guidance to librarians and, particularly, to students and new researchers who have encountered the remnants of, or clues to, ‘lost’ libraries and wondered where to go from there. As such, the article reviews the approaches used in previous reconstructions and considers whether these might be distilled into a reconstruction checklist which may guide the researcher as to actions to take and issues to consider when embarking on their reconstruction project.
Modeling of the impedance data of gadolinia doped ceria based actuators: a distribution function of relaxation times and machine learning approach
Authors: Paul Tanmoy
Published: June 2020

Gadolinia-doped ceria is one of the most extensively examined oxide ion conductors to exhibit large nonclassical electrostriction. The electromechanical response depends on the grain and grain boundaries which can be probed using electrochemical impedance spectroscopy. In this study, we have modeled the impedance spectra from buckled and free standing gadolinia doped ceria (Gd0.2Ce0.8O1.9) membrane in Al/Ti/Gd0.2Ce0.8O1.9/Ti/Al electromechanical device, at different AC excitation voltages (2, 4, 6, 8 and 10 V), and starting from room temperature to 100 °C. The analysis of impedance spectrum is commonly done by equivalent circuit modeling to obtain the resistors (

R

) and capacitors (

C

). However, to overcome the inherent problems like non-uniqueness, over fitting, presently different approaches have been chosen such as impedance spectroscopy genetic programming (ISGP) and artificial neural networks (ANNs). ISGP finds an analytic form of the distribution function of relaxation times (DFRTs) using impedance spectra. The DFRT analysis reveals that the grain boundary capacitance for the membrane ∼10−8–10−9 F decreases with increasing temperature and excitation voltages. Besides, neural networks, which are optimized by Bayesian regularization, simulate both the real and imaginary parts of impedance following the pattern of experimental data up to several Hz. The DFRT analysis on this simulated impedance data shows an effect of grain boundaries. Indeed, ANNs as optimized by Levenberg-Marquardt method, can estimate the

R

and

C

’s for present system with maximum relative errors of 24% and 22%, respectively.
Dynamic signatures of mode competition in optically injected high-β lasers
Authors: Lingnau Benjamin , Schicke David , Eichelmann Marcel , Lüdge Kathy
Published: June 2020

In this paper we theoretically investigate the statistical light-emission properties of an optically injected bimodal quantum-dot micropillar laser with high spontaneous emission rates. The nanostructured device is described in terms of a stochastic, semiclassically derived rate equation model. We focus on the stochastic switching dynamics between the two fundamental modes and correlate the results with an in-depth bifurcation analysis of the underlying deterministic dynamics. By analyzing different statistical measures, e.g. average intensity, auto- and cross-correlation functions, as well as dwell-time distributions, we give a road map on how to unravel the different dynamic regimes in the presence of large noise from experimentally accessible quantities.
Theoretical design of mid-infrared interband cascade lasers in SiGeSn system
Authors: Li Yuan , Song Zhigang , Li Zeyu , Sun Greg , Tan Chuan Seng , Fan Weijun , Wang Qi Jie
Published: June 2020

By carefully analyzing the latest composition-dependent parameters of SiGeSn alloys, we come to realize that this system could provide type-II energy band alignment at direct bandgap condition. The discovery inspires us to explore the mid-infrared interband cascade laser (ICL) in SiGeSn system. Based on the eight-band k ⋅ p model, we theoretically design three schemes of ICL, in which the active region and the carrier injectors are optimized simultaneously. Afterward, the properties of TE-mode optical gain spectrums and differential gain are investigated individually for each scheme. Furthermore, the spontaneous emission spectrums and radiative current density are also calculated. Our theoretical results indicate that the active region composed of double-electron and triple-hole quantum wells has the best gain performance, reaching 660 cm−1 for a single period of the ICL under 7.8 × 1018 cm−3 injected electron density. This work opens up another type of infrared lasers that can be developed from the group-IV system, offering a new pathway to achieving the monolithic integration in Si photonics.
A 3D biophysical model for cancer spheroid cell-enhanced invasion in collagen-oriented fiber microenvironment*
Authors: Hai Miaomiao , Liu Yanping , Xiong Ling , Li Guoqiang , Wang Gao , Zhang Hongfei , Shuai Jianwei , Chen Guo , Liu Liyu
Published: June 2020

The process of in situ tumors developing into malignant tumors and exhibiting invasive behavior is extremely complicated . From a biophysical point of view, it is a phase change process affected by many factors, including cell-to-cell, cell-to-chemical material, cell-to-environment interaction, etc. In this study, we constructed spheroids based on green fluorescence metastatic breast cancer cells MDA-MB-231 to simulate malignant tumors in vitro, while constructed a three-dimensional (3D) biochip to simulate a micro-environment for the growth and invasion of spheroids. In the experiment, the 3D spheroid was implanted into the chip, and the oriented collagen fibers controlled by collagen concentration and injection rate could guide the MDA-MB-231 cells in the spheroid to undergo directional invasion. The experiment showed that the oriented fibers greatly accelerated the invasion speed of MDA-MB-231 cells compared with the traditional uniform tumor micro-environment, namely obvious invasive branches appeared on the spheroids within 24 hours. In order to analyze this interesting phenomenon, we have developed a quantitative analyzing approach to explore strong angle correlation between the orientation of collagen fibers and invasive direction of cancer cell. The results showed that the oriented collagen fibers produced by the chip can greatly stimulate the invasion potential of cancer cells. This biochip is not only conducive to modeling cancer cell metastasis and studying cell invasion mechanisms, but also has the potential to build a quantitative evaluation platform that can be used in future chemical drug treatments.
A high performance fast-Fourier-transform spectrum analyzer for measuring spin noise spectrums*
Authors: Tong Yu , Wang Lin , Zhang Wen-Zhe , Zhu Ming-Dong , Qin Xi , Jiang Min , Rong Xing , Du Jiangfeng
Published: June 2020

A high performance fast-Fourier-transform (FFT) spectrum analyzer, which is developed for measure spin noise spectrums, is presented in this paper. The analyzer is implemented with a field-programmable-gate-arrays (FPGA) chip for data and command management. An analog-to-digital-convertor chip is integrated for analog signal acquisition. In order to meet the various requirements of measuring different types of spin noise spectrums, multiple operating modes are designed and realized using the reprogrammable FPGA logic resources. The FFT function is fully managed by the programmable resource inside the FPGA chip. A 1 GSa/s sampling rate and a 100 percent data coverage ratio with non-dead-time are obtained. 30534 FFT spectrums can be acquired per second, and the spectrums can be on-board accumulated and averaged. Digital filters, multi-stage reconfigurable data reconstruction modules, and frequency down conversion modules are also implemented in the FPGA to provide flexible real-time data processing capacity, thus the noise floor and signals aliasing can be suppressed effectively. An efficiency comparison between the FPGA-based FFT spectrum analyzer and the software-based FFT is demonstrated, and the high performance FFT spectrum analyzer has a significant advantage in obtaining high resolution spin noise spectrums with enhanced efficiency.
Fabrication and performance evaluation of GaN thermal neutron detectors with 6LiF conversion layer*
Authors: Zhu Zhifu , Sun Zhijia , Zou Jijun , Tang Bin , Xiu Qinglei , Wang Renbo , Qu Jinhui , Deng Wenjuan , Wang Shaotang , Peng Junbo , Wang Zhidong , Tang Bin , Zhang Haiping
Published: June 2020

A GaN-based pin neutron detector with a 6LiF conversion layer was fabricated, and can be used to detect thermal neutrons. Measurement of the electrical characteristic of the GaN-based pin neutron detector showed that the reverse leakage current of the neutron detector was reduced significantly after deposition of a 6LiF conversion layer on the detector surface. The thermal neutrons used in this experiment were obtained from an 241Am–Be fast neutron source after being moderated by 100-mm-thick high-density polyethylene. The experimental results show that the detector with 16.9-μm thick 6LiF achieved a maximum neutron detection efficiency of 1.9% at a reverse bias of 0 V, which is less than the theoretical detection efficiency of 4.1% calculated for our GaN neutron detectors.
Design and investigation of dopingless double-gate line tunneling transistor: Analog performance, linearity, and harmonic distortion analysis*
Authors: Xu Hui-Fang , Han Xin-Feng , Sun Wen
Published: June 2020

The tunnel field-effect transistor (TFET) is proposed by using the advantages of dopingless and line-tunneling technology. The line tunneling is created due to the fact that the gate electric field is aligned with the tunneling direction, which dramatically enhances tunneling area and tunneling current. Moreover, the effects of the structure parameters such as the length between top gate and source electrode, the length between top gate and drain electrode, the distance between bottom gate and drain electrode, and the metal position on the on-state current, electric field and energy band are investigated and optimized. In addition, analog/radio-frequency performance and linearity characteristics are studied. All results demonstrate that the proposed device not only enhances the on/of current ratio and reduces the subthreshold swing, but also offers eight times improvement in cut-off frequency and gain band product as compared with the conventional point tunneling dopingless TFET, at the same time; it shows better linearity and small distortions. This proposed device greatly enhances the potential of applications in dopingless TFET.
Hardening effect of multi-energyW2+-ion irradiation on tungsten–potassium alloy*
Authors: Song Yang-Yi-Peng , Qiu Wen-Bin , Chen Long-Qing , Yang Xiao-Liang , Deng Hao , Liu Chang-Song , Zhang Kun , Tang Jun
Published: June 2020

Tungsten is one of the most promising plasma-facing materials (PFMs) to be used in the nuclear fusion reactor as divertor material in the future. In this work, W2+-ions bombardment is used to simulate the neutron irradiation damage to commercial pure tungsten (W) and rolled tungsten–potassium (W–K). The 7 MeV of 3 × 1015 W2+-ions/cm2, 3 MeV of 4.5 × 1014 W2+, and 2 MeV of 3 × 1014 W2+-ions/cm2 are applied at 923 K in sequence to produce a uniform region of 100 nm–400 nm beneath the sample surface with the maximum damage value of 11.5 dpa. Nanoindentation is used to inspect the changes in hardness and elastic modulus after self-ion irradiation. Irradiation hardening occurred in both materials. The irradiation hardening of rolled W–K is affected by two factors: one is the absorption of vacancies and interstitial atoms by potassium bubbles, and the other is the interaction between potassium bubbles and dislocations. Under the condition of 11.5 dpa, the capability of defect absorption can reach a threshold. As a result, dislocations finally dominate the hardening of rolled W–K. Specific features of dislocation loops in W–K are further observed by transmission electron microscopy (TEM) to explain the hardening effect. This work might provide valuable enlightenment for W–K alloy as a promising plasma facing material candidate.
Symmetry-broken silicon disk array as an efficient terahertz switch working with ultra-low optical pump power*
Authors: Han Zhanghua , Jiang Hui , Tan Zhiyong , Cao Juncheng , Cai Yangjian
Published: June 2020

The advancement of terahertz technology in recent years and its applications in various fields lead to an urgent need for functional terahertz components, among which a terahertz switch is one example of the most importance because it provides an effective interface between terahertz signals and information in another physical quantity. To date many types of terahertz switches have been investigated mainly in the form of metamaterials made from metallic structures and optically-active medium. However, these reported terahertz switches usually suffer from an inferior performance, e.g., requiring a high pump laser power density due to a low quality factor of the metallic metamaterial resonances. In this paper, we report and numerically investigate a symmetry-broken silicon disk based terahertz resonator array which exhibits one resonance with ultrahigh quality factor for normal incidence of the terahertz radiations. This resonance, which can never be excited for regular circular Si disks, can help to realize a superior terahertz switch with which only an ultra-low optical pump power density is required to modify the free carrier concentration in Si and its refractive index in the terahertz band. Our findings demonstrate that to realize a high terahertz transmittance change from 0 to above 50%, the required optical pump power density is more than 3 orders of magnitude smaller than that required for a split-ring resonator (SRR) based terahertz switch reported in the literature.
Band alignment of p-type oxide/ε-Ga2O3 heterojunctions investigated by x-ray photoelectron spectroscopy*
Authors: Rao Chang , Fei Zeyuan , Chen Weiqu , Chen Zimin , Lu Xing , Wang Gang , Wang Xinzhong , Liang Jun , Pei Yanli
Published: June 2020

The ε-Ga2O3 p–n heterojunctions (HJ) have been demonstrated using typical p-type oxide semiconductors (NiO or SnO). The ε-Ga2O3 thin film was heteroepitaxial grown by metal organic chemical vapor deposition (MOCVD) with three-step growth method. The polycrystalline SnO and NiO thin films were deposited on the ε-Ga2O3 thin film by electron-beam evaporation and thermal oxidation, respectively. The valence band offsets (VBO) were determined by x-ray photoelectron spectroscopy (XPS) to be 2.17 eV at SnO/ε-Ga2O3 and 1.7 eV at NiO/ε-Ga2O3. Considering the bandgaps determined by ultraviolet-visible spectroscopy, the conduction band offsets (CBO) of 0.11 eV at SnO/ε-Ga2O3 and 0.44 eV at NiO/ε-Ga2O3 were obtained. The type-II band diagrams have been drawn for both p–n HJs. The results are useful to understand the electronic structures at the ε-Ga2O3 p–n HJ interface, and design optoelectronic devices based on ε-Ga2O3 with novel functionality and improved performance.
Symmetry-controlled edge states in graphene-like topological sonic crystal*
Authors: Yang Zhang-Zhao , Chen Jin-Heng , Peng Yao-Yin , Zou Xin-Ye
Published: June 2020

Unique topological states emerged in various topological insulators (TI) have been proved with great application value for robust wave regulation. In this work, we demonstrate the parity inversion related to the definition of the primitive cell in one common lattice, and realize a type of symmetry-controlled edge states confined on the zigzag interfaces of the graphene-like sonic topological crystal. By simply sliding the selected ‘layer’ near the interface, the coupling of the pseudospin states induced by the multiple scattering for the C
6v
lattice results in the adjustment of the edge states. Based on the physics of the states, we experimentally propose a prototype of acoustic topological filter hosting multiple channels with independent adjustable edge states and realize the selective high transmission. Our work diversifies the prospects for the applications of the gapped edge states in the robust wave regulation, and proposes a frame to design new topological devices.
Measuring orbital angular momentum of acoustic vortices based on Fraunhofer’s diffraction*
Authors: Gong Chao-Fan , Li Jing-Jing , Guo Kai , Zhou Hong-Ping , Guo Zhong-Yi
Published: June 2020

Acoustic vortex (AV) beam is triggering the significant research interest in information and communication sciences due to its infinite and mutual orthogonal orbital angular momentums (OAMs). Therefore, measuring the topological charges of an AV beams become a task with great significance. In this work, we present a Fraunhofer diffraction (FD) pattern of an AV beam that can be used to quantitatively detect the OAMs of AV beams. We both theoretically and numerically investigate the FD patterns of AV beams passing through a multipoint interferometer (MPI). It is demonstrated that the topological charges of the AV beams can be determined from the interference intensity patterns. The proposed method may pave the way to the practical applications of AV beams.
Dynamic recombination of triplet excitons in polymer heterojunctions*
Authors: Wang Ya-Dong , Liu Jian-Jun , Wang Xi-Ru , Liu Yan-Xia , Meng Yan
Published: June 2020

The dynamic recombination of two triplet excitons with opposite spins in the heterojunction structure has been investigated using a nonadiabatic evolution method. We demonstrate that luminous composite states including the excited polaron and the biexciton can be formed efficiently via the triplet exciton–triplet exciton reaction in the heterojunction and therefore this reaction can enhance the electroluminescence efficiency considerably, which is consistent qualitatively with experimental observations. Meanwhile, we find that, although the heterojunctions are beneficial to the generation of luminescent particles, large band offset caused by the heterojunction structure is not helpful to improve the electroluminescence efficiency. In addition, the mechanism of the triplet exciton–triplet exciton reaction in heterojunction is different from that of two similar coupling chains. Our results may deepen the understanding of the electroluminescence mechanism in polymer light-emitting devices.
Absolute cross sections of ultra-soft x-ray radiation in electron scattering upon atoms
Authors: Kornev A S , Zon B A , Amusia M Ya
Published: June 2020

Synopsis

The soft-photon approximation (SPA) is shown to give quantitative interpretation of absolute measurement of bremsstrahlung (BrS) cross section, σ, on atomic targets in the region of large wavelengths λ, for which σ∼ 1/λ2.
Towards understanding the electronic structure and ion fragmentation patterns of indole and related compounds
Authors: Sa’adeh H , Plekan O , Ponzi A , Toffoli D , Bolognesi P , Chiarinelli J , Castrovilli M C , Vozzi C , Faccialà D , Devetta M , Ciavardini A , Avaldi L , Coreno M , Callegari C , Richter R , Prince K C
Published: June 2020

Synopsis

Electronic structure and VUV-induced fragmentation of selected molecules of the indole family have been studied using valence photoemission spectroscopy (PES), core X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) and Photo-Electron Photo-Ion Coincidence (PEPICO).
Benchmark calculations for photoionization of neutral iron
Authors: Zatsarinny O , Bartschat K , Fernandez-Menchero L , Tayal S S
Published: June 2020

Synopsis

The B-spline R-matrix method is used to investigate the photoionization of neutral iron from its ground and the lowest 43 excited states in the energy region from the ionization thresholds to 2 Ry. The sensitivity of the predictions is checked by comparing results obtained in different approximations. Including all terms from the 3d64p and 3d54s4p configu-rations considerably changes both the low-energy resonance structure and the background cross sections.
An investigation of photo-double ionization in benzene
Authors: Howard J , Sokell E , Bolognesi P , Avaldi L
Published: June 2020

Synopsis

A photo-double ionization (PDI) coincidence technique has been used to study electron correlation as a function of photon impact energy on Benzene (C6H6). The simultaneous emission of two photoelectrons from the benzene π orbital has been measured using two sets of hemispherical electron energy analysers. Angle resolved single and coincidence photoelectron spectra are reported, providing new data on the PDI mechanism.
The Small Quantum System (SQS) Instrument at European XFEL: Results of commissioning and first experiments
Authors: Meyer M , Baumann T M , Achner A , Boll R , De Fanis A , Grychtol P , Ilchen M , Mazza T , Montaño J , Music V , Ovcharenko Y , Rennhack N , Rivas D E , Wagner R , Ziołkowski P , Rolles D , Walter P , Erk B , Keitel B , Plönjes E , Mann K , Lange S , Schäfer B , Chalupský J , Burian T , Juranova K , Vyšín L , Hájková V , Juha L
Published: June 2020

Synopsis

The Small Quantum System (SQS) instrument on the soft X-ray undulator SASE3 of the European XFEL went into operation during 2018. We present first results from the instrument characterizing the focus properties and the time-of-flight as well as velocity map imaging spectrometers of the AQS chamber.
Ultrafast ionization and fragmentation dynamics of polycyclic atomatic hydro-carbons by XUV radiation
Authors: Manschwetus B , Chopra P , Tikhonov D , Köckert H , Gruet S , Lahl J , Maclot S , Peschel J , Steber A L , Lee J W L , Boll R , Bari S , Dörner S , Allum F , Erk B , He Lanhai , Passow C , Rompotis D , Lemmens A , Mason R , Heathcote D , Burt M , Wiese J , Johny M , Müller E , Ziaee F , Kazemi M M , Schirmel N , Olshin P , Cheng X , Ramm D , Trippel S , Mullins T , Rijs A , Küpper J , Vallence C , Brouard M , Rolles D , Johnsson P , Schnell M
Published: June 2020

Synopsis

In the interstellar medium polycyclic aromatic hydrocarbon molecules (PAH) are exposed to strong ionizing radation leading to complex organic photochemistry. We investigated these ultrafast fragmentation reactions after ionization of the PAHs phenanthrene, fluorene and pyrene at a wavelength of 30.3 nm using pump probe spectroscopy at a free electron laser. We observe double ionization and afterwards hydrogen abstraction and acetylene loss with characteristic time scales for the reaction processes below one hundred femtoseconds.
Rydberg polyatomic molecules: Electronic structure and experimental proposal for their creation
Authors: González-Férez R , Rittenhouse S T , Schmelcher P , Sadeghpour H R
Published: June 2020

Synopsis

We describe the electronic structure and main features of ultralong range Rydberg molecules formed by a Rydberg atom, either Rb or K, and the heteronuclear diatomic molecule KRb. By analyzing their electronic structure, we propose a protocol to create these molecules experimentally from a mixture of ultracold atoms and ultracold molecules.
Laser-Assisted Self Induced Feshbach Resonance : a new tool for controlling ultracold atomic collisions
Authors: Devolder A , Luc-Koenig E , Atabek O , Desouter-Lecomte M , Dulieu O
Published: June 2020

Synopsis

We propose a new kind of Feshbach Resonance (FR) : the Laser-Assisted Self-Induced Feshbach Resonance (LASIFR), applicable for all mixtures of ultracold atoms. The interspecies scattering length characterizing elastic collisions, a key property for many applications of ultracold quantum gases, can be controlled by a LASIFR through the laser intensity and the frequency. It can be also used for the formation of ultracold polar molecules.
Quantum phases of biased bosonic ladders subject to a magnetic field
Authors: Qiao X , Zhang X B , Zhang A X , Yu Z F , Xue J K
Published: June 2020

Synopsis

The quantum phase transition of the Plane Wave I phase, the Plane Wave II phase, and interestingly, a new phase named Moving Biased Vortex phase are revealed in the biased bosonic two-leg ladder system.
Atomic and molecular Auger decay in CHCl3 molecule
Authors: Vasconcelos D N , Santos A C F , Morcelle V , Macdonald M A , Sant’Anna M M , Tenório B N C , Rocha A B , Bonfin V B , Appathurai N , Zuin L
Published: June 2020

Synopsis

The dissociation following Cl 2p core–shell excitation in CHCl3 molecule is studied. It is observed the presence of atomic Auger lines associated with the decay of dissociated Cl* atoms. Calculations were compared with the corresponding experimental photoexcited and photoionized spectra to study the competition between the atomic and molecular Auger decays.
Solitons in two-leg bosonic ladder subject to an artificial magnetic field
Authors: Cai L X , Zhang A X , Xue J K
Published: June 2020

Synopsis

The nonlinear dynamics in two-leg ladder system subject to an artificial magnetic field are discussed in detail. The critical conditions for the formation of soliton and for the transition from diffusion to self-trapping are presented, and confirmed by the numerical simulations of the full discrete nonlinear Schrödinger equation.
Hybrid Electrostatic Ion Beam Trap (HEIBT): design and simulation of ion-ion and ion-neutral low-energy collisions and ion-laser photoreactions
Authors: Shahi A , Singh R , Ossia Y , Rappaport M L , Heber O , Zajfman D , Strasser D
Published: June 2020

Synopsis

A new hybrid electrostatic ion beam trap (HEIBT) is designed and simulated for low-energy ion-ion, ion-neutral merged beam collision studies as well as ion-laser interaction experiments. The HEIBT is made possible by the design of dichroic electrostatic mirrors that reflect or transmit ion beams of different charge and energy. The experimental setup allows fragment imaging detection of the investigated reaction products ejected outside the trap.
Theoretical study of the dielectronic recombination process of Mg-like W62+ ions
Authors: Xie L Y , Nai G W , Jiang J , Zhang D H , Dong C Z
Published: June 2020

Synopsis

The dielectronic recombination of Mg-like W62+ (3s2) ions was studied using the flexible atomic code based on the relativistic configuration interaction method with considering Breit and QED corrections. Theoretical results are compared with the experimental results from electron beam ion trap, good consistency is obtained.
Ultrafast laser induced structural dynamics probed by time-resolved photoelectron spectroscopy
Authors: Villa M de Anda , Lévy A , Gaudin J , Bouillaud R , Descamps D , Dorado B , Fedorov N , Grisenti R , Hatifi M , Jouin H , Lamour E , Macé S , Martin P , Petit S , Prigent C , Sobierajski R , Steydli S , Trassinelli M , Wawro A , Vernhet D
Published: June 2020

Synopsis

This work aims to study laser-induced lattice dynamics when there is strong electron-lattice temperature non-equilibrium for which the material properties are poorly known. The proposed experimental technique is time-resolved photoelectron spectroscopy (Tr-PES). The main challenges of such technique are the superposition of pump and probe spectra and the distortion of the probe spectra due to the interaction with pump-induced electrons, called space charge effect (SCE). We strongly reduced this effect by tuning the 100eV XUV beamline we have developed, enabling us to investigate Copper samples.
Theoretical investigation of electron-ion recombination process of Fe14+ ion
Authors: Xie L Y , Pan J P , Zhang D H , Jiang J , Dong C Z
Published: June 2020

Synopsis

The Δn=1 dielectronic, trielectronic, and quadruelectronic recombinations of Fe14+ ion are systematically studied using the flexible atomic code based on the relativistic configuration interaction method. The theoretical rate coefficients are identified and compared with the experimental measurements at heavy-ion storage ring (TSR), good agreement is obtained.
Autodetachment spectroscopy of the metastable HD− and

D2−

anions
Authors: Marion R , Číźek M , Urbain X
Published: June 2020

Synopsis

The autodetachment spectrum of decaying HD− and

D
2
−

has been recorded with a velocity-map imaging spectrometer. Coincident detection of the neutral molecule permits the selection of events occuring in the center of the spectrometer. The discrete features of the spectrum are assigned to transitions between well identified ro-vibrational levels. Energies, lifetimes and branching ratios predicted with the non-local potential framework developed for associative detachment satisfactorily reproduce the experimental results.
Spectroscopy and kinetics of IR laser interaction with atmospheric molecules: Effects of cooling and chaos
Authors: Ternovsky E , Glushkov A , Svinarenko A , Bunyakova Yu
Published: June 2020

Synopsis

Spectroscopy and kinetics of energy and heat exchange in the mixture CO2-N2-H2O under passing the CO2laser pulses is studied. To describe the energy exchange and relaxation processes in the CO2.- N2- H2O mixture, which interacts with a laser pulse, we use the modified 3-mode model of the kinetic processes New data on the resonant absorption relative coefficient α(CO2) for the European mid-latitude atmospheric model are presented. It is also studied a chaotic behaviour of the carbon and nitrogen dioxide concentration time series (Munich & Gdansk reg.) and the low-D chaos effect is found.
Double-continuum R-matrix theory and codes for many-electron atoms: ionizing electron collisions and time-dependent laser-induced double-ionization
Authors: Plummer M , Noble C J
Published: June 2020

Synopsis

An extension of ab initio many-electron R-matrix theory is described which is relevant both to the time-dependent description of excitation and single and double ionization of atoms in laser pulses, and to time-independent calculation of intermediate energy electron collisions where ionized states of the target atom can be excited. Corresponding general many-electron ‘inner region’ code modules have been developed for use in combination with existing R-matrix method codes for diverse applications with up to two electrons explicitly described by a continuum orbital basis.
Role of methylation in electron scattering on X(CH3)4 (X = C, Si, Ge) molecules
Authors: Stefanowska-Tur S , Szmytkowski Cz , Ptasińka-Denga E , Mozejko P
Published: June 2020

Synopsis

Total cross sections (TCS) for low-energy electron scattering from X(CH3)4 (where X = C, Si, Ge) molecules have been measured using linear transmission method. Present results and those obtained previously for XH4 molecules were used to determine how methylation of the target is reflected in TCS energy dependence.
Investigation of TEOP transitions in dielectronic recombination with H-like ions
Authors: Lyashchenko K N , Andreev O Yu , Yu D
Published: June 2020

Synopsis

We consider theoretically the process of dielectronic recombination (DR) with H-like ions where two-electron one-photon (TEOP) transitions take place. We focus our attention on the channel with transitions to the ground state of the He-like ions and emission of Kαα
photon. Total and differential cross sections of DR with TEOP are calculated for wide range of H-like ions: from B4+ to Xe53+. The resonant Fano-like structure of the cross section is observed. The resonant energies, widths and TEOP transition probabilities are calculated.
Cascade and direct processes in multiple Auger decay of core-excited states of N2
Authors: Odagiri T , Taniguchi T , Kaneyasu T , Tanaka H , Adachi J , Lablanquie P , Hikosaka Y
Published: June 2020

Synopsis

We report here a detailed experimental study on multiple Auger decay after core excitation into the π*
valence and Rydberg orbitals in N2 by an electron-electron coincidence technique.
On the effect of cascade transitions after electron-impact excitation of Zn by spin-polarized electrons
Authors: Bartschat K , Zatsarinny y , Bostock C J , Fursa D V , Bray I , Grum-Grzhimailo A N
Published: June 2020

Synopsis

We investigate the possible effect of cascade transitions from the (4s5p)3P0,1,2 states to the (4s5s)3S1 state of Zn. Our calculations suggest that the excitation cross sections and the polarization of the cascade radiation cannot explain the serious controversy between two existing experimental datasets below the cascade threshold and raise additional questions regarding the measurements at higher energies.
Electron impact excitation of highly charged Ge-Like Xe ion
Authors: Bharti S , Sharma L , Srivastava R
Published: June 2020

Synopsis

A systematic study of electron impact excitation of Ge-like highly charged xenon ions have been carried out in Extreme Ultraviolet (EUV) range within fully relativistic multiconfiguration Dirac-Fock framework. The cross section calculation reported here are performed for dipole allowed transitions for Xe22+ ions from ground state 4s24p2
to 4s24p3 and 4s24p4d excited fine structure levels. The analytic fitting for the cross section data for incident electron energy range within 50 to 1500 eV have been provided for further applications in various plasma diagnostic techniques.
Development of accurate anharmonic vibrational state theory using a novel vibrational coordinate based on backflow transformation
Authors: Ishii K , Tashikawa M , Kita Y
Published: June 2020

Synopsis

The anharmonic vibrational state theory based on quantum Monte Carlo method is one of the most accurate methods to solve a vibrational Schrödinger equation of molecular systems. In anharmonic vibrational state analyses, one should take account of the inter-mode couplings, which cannot be included by the conventional normal mode coordinates only. In this study, thus, we have developed a novel vibrational coordinate based on backflow transformation which enable us to take correlation effects in quantum many-body systems directly.
Nonlocal treatment of resonant vibrational excitation in electron-dioxygen collision
Authors: Alt V , Houfek K
Published: June 2020

Synopsis

The cross sections for vibrational excitations of O2 through collisions with electron are calculated using the nonlocal discrete-state-in-continuum model and its local approximation and compared to experimental results.
Distribution of dipole oscillator strengths for the formation of excited hydrogen atom from C2H2
Authors: Kumagai Y , Odagirit T , Nakano M , Suzuki I H , Hosaka K , Kitajima M , Kouchi N
Published: June 2020

Synopsis

Dipole oscillator strengths for the formation of excited hydrogen atom from C2H2 were measured to investigate formation and decay of molecular superexcited states. It seems that non-adiabatic transition plays an important role in the formations of the hot hydrogen atom.