bluuebunny/crossref_metadata_2025 huggingface dataset:
Instability of a heavy gas layer induced by a cylindrical convergent shock
Authors: Li Jianming , Ding Juchun , Luo Xisheng , Zou Liyong
Published: April 2022

The instability of a heavy gas layer (SF6 sandwiched by air) induced by a cylindrical convergent shock is studied experimentally and numerically. The heavy gas layer is perturbed sinusoidally on its both interfaces, such that the shocked outer interface belongs to the standard Richtmyer–Meshkov instability (RMI) initiated by the interaction of a uniform shock with a perturbed interface, and the inner one belongs to the nonstandard RMI induced by a rippled shock impacting a perturbed interface. Results show that the development of the outer interface is evidently affected by the outgoing rarefaction wave generated at the inner interface, and such an influence relies on the layer thickness and the phase difference of the two interfaces. The development of the inner interface is insensitive (sensitive) to the layer thickness for in-phase (anti-phase) layers. Particularly, the inner interface of the anti-phase layers presents distinctly different morphologies from the in-phase counterparts at late stages. A theoretical model for the convergent nonstandard RMI is constructed by considering all the significant effects, including baroclinic vorticity, geometric convergence, nonuniform impact of a rippled shock, and the startup process, which reasonably predicts the present experimental and numerical results. The new model is demonstrated to be applicable to RMI induced by a uniform or rippled cylindrical shock.
Parametric analysis of the effects of blade exit angle on the cavitation characteristics in a hydraulic torque converter
Authors: Guo Meng , Liu Cheng , Zhang Jiahua , Liu Shiqi , Ke Zhifang , Yan Qingdong , Khoo Boo Cheong
Published: April 2022

Hydraulic torque converters are prone to cavitation due to their high impeller rotational speeds and their complex three-dimensional flow characteristics. Since the blades are the core components of torque converters, the shapes of the blades are important to the hydraulic performance and cavitation characteristics. Different cavitation computational fluid dynamics (CFD) models for a torque converter were developed to simulate the internal cavitation flow for different pump and turbine blade exit angles, and the influence of the blade angles on the cavitation characteristics and cavitation flow field in the torque converter was investigated. Experimental prototypes were produced and tested for verification. The results indicate that the pump and turbine blade exit angles had significant effects on the cavitation number of the torque converter. Increasing the pump and turbine blade exit angles promotes the generation and intensification of cavitation, resulting in severe changes in the shapes and locations of the cavitation bubbles due to changes in the fluid impact angles. Additionally, cavitation is quickly suppressed and the performance is improved when the blade exit angles are reduced within an appropriate range, in particular, that of the turbine blade. These research results can provide guidance for the design of a high-performance hydraulic torque converter cascade system and the suppression of cavitation for practical engineering applications.
Aerodynamic performance of a bio-inspired flapping wing with local sweep morphing
Authors: Wang Chunyu , Liu Yi , Xu Duo , Wang Shizhao
Published: April 2022

Birds and bats frequently reconfigure their wing planform through a combination of flapping and local sweep morphing, suggesting a possible approach for improving the performance of micro aerial vehicles. We explore the effects of combined flapping and local sweep morphing on aerodynamic performance by employing a bio-inspired two-jointed flapping wing with local sweep morphing. The bio-inspired wing consists of inner and outer sections, which flap around the root joint (shoulder) and the midspan joint (wrist), respectively. The aerodynamic forces and the unsteady vortex structures are evaluated by numerically solving the incompressible Navier–Stokes equations. The results show that combined flapping and local sweep morphing can significantly enhance the aerodynamic performance. In particular, the average lift coefficient is 1.50 times greater than that of simple gliding with single local sweep morphing. Combined flapping and local sweep morphing also have a relatively high pitch moment and shift the aerodynamic center position backward, producing advantages in terms of maneuverability/agility and stability. We find that the vortex structures associated with the combined motion feature midspan vortices, which arise from the leading-edge vortices of the inner wing and contribute to the enhanced aerodynamic performance. We show that the kinematics of combined flapping and local sweep morphing can be further optimized if the midspan vortices are captured by the outer wing.
Long-wave instability of a regularized Bingham flow down an incline
Authors: Calusi B. , Farina A. , Fusi L. , Rosso F.
Published: April 2022

We investigate the linear stability of a flow down an incline when the fluid is modeled as a regularized Bingham-like fluid, i.e., a material whose constitutive equation is smoothed out. We perform a theoretical analysis by using the long-wave approximation method. The results show the existence of a critical condition for the onset of instability, which arises when the Reynolds number is above a critical threshold that depends on the tilt angle and on rheological parameters. The comparison of our findings with experimental studies is rather satisfactory.
A comparative study on post-stall flow separation control mechanism of steady and unsteady plasma actuators
Authors: Yang Peng-Yu , Zhang Xin , Yue Ting-Rui
Published: April 2022

In order to improve the aerodynamic performance of the wing at post-stall conditions, the experimental comparative investigations on the flow separation control over an ONERA 212 airfoil using steady and unsteady plasma actuators are carried out at Reynolds number of 3.1 × 105. The duty cycle ratio is fixed at 80%, and the non-dimensional unsteady frequency F+ is varied from 0.04 to 1. The lift coefficients are increased by 39.6% and 66%, respectively, after steady and unsteady operations (F+ = 0.08) at an angle of attack of 18°, which indicates that the unsteady actuation is more efficient than steady operation. Meanwhile, the study provides new insight into understanding the post-stall separation flow controlling mechanism. First, different from the general view that the injection of momentum is the controlling mechanism of steady operation, flow control using the steady actuation experiences four stages, namely, flow separation, promoting the instability of the separated shear layer to produce large-scale spanwise vortices, flow re-attachment, and the continuous generation of small-scale vortices in the separated shear layer. Second, flow control with the unsteady operation consists of several quasi-periodic flow processes. Each quasi-cycle is composed of three stages, namely, flow separation, promoting the separation of shear layer instability to produce large-scale spanwise vortices, and flow re-attachment. The off-time of the plasma actuator plays an important role in realizing the control effect of the unsteady actuation, and an effective strategy to promote the control effect of the unsteady operation is proposed based on the propagation time of the induced spanwise vortex.
Role of miRNAs in preimplantation embryo development and their potential as embryo selection biomarkers
Authors: Esmaeilivand Masoumeh , Abedelahi Ali , Hamdi Kobra , Farzadi Laya , Goharitaban Sepide , Fattahi Amir , Niknafs Behrooz
Published: April 2022

Context MicroRNAs (miRNAs) play different roles in oocyte fertilisation, degradation of maternal transcripts, embryo development, and implantation. During in vitro fertilisation (IVF), different miRNAs are released from embryos into the spent culture media (SCM) that can potentially reflect the status of the embryo. Aims This study is the assessment of miRNAs, which secreted in SCM during the IVF cycles can be used as noninvasive biomarkers to predict an embryo’s ability to form a blastocyst, implant, and give live birth. Methods Systematic literature search was conducted to review all recent studies about miRNAs as potential non-invasive biomarkers for selecting the best embryos in the assisted reproductive technology (ART) cycle. Key results Studies have shown that levels of some miRNAs in the SCM have an association with the implantation potential and pregnancy outcome of the embryo. Conclusions Embryo-secreted miRNAs can be used as potential non-invasive biomarkers for selecting the best embryos in the ART cycle. Unfortunately, few human studies evaluated the association between ART outcomes and miRNAs in SCM. Implications This review can pave the way for further miRNAs transcriptomic studies on human embryo culture media and introducing a specific miRNA profile as a multivariable prediction model for embryo selection in IVF cycles.
Internet memes we live by (and die by)
Authors: Xie Chaoqun
Published: April 2022

In the internet age, memes are at once products and driving forces of social practices. A meme contains a memetic message and a meme output, and boasts, if guided by a pragmatic way of thinking, several features, including, but not limited to, salience, frequency, adaptability, argumentativity, sociality, embeddedness, embodiedness, locality, relativity, emotionality and dynamicity. The current global COVID-19 pandemic serves as a fitting and timely touchstone to testify how human beings are surrounded by numerous good and evil memes in the online world, and how internet memes, as can be seen from the illustration of two specific memes, namely, the ‘stay home, stay safe’ meme and the ‘wear a mask’ meme, are impacting human life-worlds, online and offline, with their transformative power, be it constructive or destructive. Moreover, researching how memes plays a decisive part in internet-mediated interaction provides a lens of insight through which ‘deep states’ of human nature of both self and others can be uncovered and through which what Nietzsche (2002, 2017) called “a revaluation of values” is possible.
Stylistic humor across modalities
Authors: Piata Anna
Published: April 2022

This paper is concerned with ‘Classical Art Memes’, a category of internet memes that distinctively derives its visual input from classical and medieval art. I specifically show that humor in Classical Art Memes arises from incongruity among different stylistic varieties, namely a colloquial linguistic expression in the text and a classical-style artwork in the image. Given that stylistic incongruity cross-cuts modalities, I further argue that Classical Art Memes make a case for what I call ‘multimodal stylistic humor’. The analysis is based on a small corpus of when-memes, whereby the image complements a when-clause. The findings of the study suggest that humor in Classical Art Memes serves to convey affective meanings that emerge from the embodied affect in the image that is textually recontextualized in contemporary terms. Such meanings ultimately convey a critical commentary on knowable features of modern life.
Cereal-legume cropping systems for enhanced productivity, food security, and resilience.
Authors: Chikowo Regis , Chirwa Rowland , Snapp Sieglinde
Published: April 2022

This chapter presents four approaches to the integration of legumes (such as soyabean, groundnut, and cowpea) in maize-dominated systems, through intercropping, efficient spatial arrangements, and legume-cereal sequences: (i) grain legume-maize rotations for increased yield stability on smallholder farms, (ii) 'doubled-up' legume technology for soil fertility maintenance and human nutrition, (iii) innovative maize-common bean (Phaseolus vulgaris) intercropping and fertilizer application for improved productivity, (iv) targeted cropping sequences (rotations adapted to farm size limitations and farmer goals) and associated elements for sustainable intensification on small farms. The first three technologies are based specifically on legumes that smallholder farmers can introduce to increase the productivity of their farms. The fourth demonstrates how different legume-based technologies can be integrated on farms with different resources, allowing farmers to diversify and intensify their production in a sustainable manner.
Improved technologies for reducing post-harvest losses.
Authors: Mutungi Christopher , Abass Adebayo , Fischer Gundula , Kotu Bekele
Published: April 2022

This chapter outlines several post-harvest loss reduction technologies validated by the Africa RISING program that will improve the efficacy of drying, threshing, and storage operations, and gives evidence of their potential impact. The chapter also provides evidence on the cumulative benefits of combining all three technologies.
Be autonomous or stay away! Providing evidence for autonomy beliefs as legitimizing myths for the stigma of schizophrenia (¡Sé autónomo o mantente al margen! Ofreciendo evidencias para las creencias en la autonomía consideradas como mitos legitimizantes para el estigma de la esquizofrenia)
Authors: Lampropoulos Dimitrios , Apostolidis Thémis
Published: April 2022

Authors suggest that in liberal contexts, groups considered as lacking autonomy, such as people with schizophrenia, can face stigma. Following Social Dominance theory, we hypothesized that perceived autonomy of people with schizophrenia mediates the relation between SDO and stigmatizing attitudes. Participants from the general population ( N = 255; 76.5% women, Mage = 25.33, SD = 12.3) responded to our questionnaire assessing one’s SDO, perceived autonomy and stigmatizing attitudes towards schizophrenia (i.e., dangerousness and desired social distance). Analysis of direct paths from SDO to perceived autonomy ( b = −.45, p < .001) and from the latter to perceived dangerousness ( b = −.33, p < .001) and to social distance ( b = −.46, p < .001), as well as analysis of indirect paths ( b = .15, p < .01) for perceived dangerousness ( b = .25, p < .001 for social distance), confirmed our hypotheses, and our model showed a good data fit. Our results provide evidence for the stigmatizing role of the autonomy ideal for people with disabilities and invite further development regarding anti-stigma efforts.
4D printing of Ni–Mn–Ga magnetic shape memory alloys: A review
Authors: Milleret Anastassia
Published: April 2022

4D printing has grown tremendously in the last decade, enabling functional structures made of smart materials to be manufactured. Current metal 4D printing research has focused on thermal shape memory alloys (SMAs) and to a lesser extent on magnetic SMAs. This review assesses the progress in 4D printing of Ni–Mn–Ga, highlighting the key challenges and opportunities for applications. The mechanism of the magnetic SMAs and the influence of 4D printing process parameters on the microstructure and material properties are explored, with an emphasis on laser powder bed fusion processing. Control of porosity, microstructure, texture and impact of post-processing on magnetic performance are the key challenges for the development of Ni–Mn–Ga 4D printing.
Review on operation of spinel-containing slags of the non-ferrous metallurgy
Authors: Kleeberg Cora
Published: April 2022

Operation of slags and their valorisation are one major topic in the metallurgical industry. Different phases within the slag have influences on the slag properties, which requires fundamental knowledge on the system to consider effective measures to reach the individual optimisation targets. Solid phases like spinels in slags have an impact on viscosity, resulting in operational issues, increased metal losses and other effects in daily operation. In this document an overview on spinel-containing slags of the non-ferrous metallurgical processes is given, with focus on operation in liquid state. It shows a summary of the current state of experimental and modelling work in this field done by different research groups. The importance of studies on thermodynamic properties and phase diagrams to solve practical operational issues is outlined.
Influence of prestress grinding hardening residual stress on rolling contact fatigue
Authors: Sun Cong , Xiu Shichao , Xing Chunsheng , Lu Hanmin , Wang Dawei , Wang Rensheng
Published: April 2022

The rolling contact fatigue is commonly seen in industrial applications. Studies mainly focus on fatigue evolution caused by heat treatment. However, the combined machining includes thermal-mechanical coupling and transformation. The generated residual stress can be another factor to decide contact fatigue. A sequent study is conducted to investigate the influence of residual stress on contact fatigue after prestress grinding hardening. To figure out the rolling crack initiation and propagation on residual stress surface, a united calculation combined with finite element method and analytic method is proposed. Based on the above analysis, the rolling contact fatigue can be adjusted by controlling the initial residual stress of machining surface, which is meaningful for surface anti-fatigue manufacturing with longer life span requirements.
The epitaxial growth of TiC on ZrC in low-carbon steel
Authors: Luo Hanyu , Cao Jianchun
Published: April 2022

In order to explore and control the precipitation behaviour of Ti-Zr composite microalloyed low-carbon steel during multi-pass deformation, the precipitation form and orientation relationship of TiC and ZrC were studied by transmission electron microscopy (TEM) in this paper. The results show that the initial precipitation of ZrC can form heterogeneous nucleation sites of TiC, and TiC particles will epitaxially grow on the surface of ZrC to form a gourd-like composite precipitate. Electron diffraction analysis shows that there are two main orientation relationships between TiC and ZrC, which are (200)TiC[Formula: see text] TiC//(200)ZrC[Formula: see text] ZrC, (020)TiC[Formula: see text] TiC//(020)ZrC[Formula: see text] ZrC.
A semi-empirical model for peak temperature estimation in friction stir welding of aluminium alloys
Authors: Ambrosio Danilo , Aldanondo Egoitz , Wagner Vincent , Dessein Gilles , Garnier Christian , Vivas Javier , Cahuc Olivier
Published: April 2022

Process parameters and base material thermal properties strongly affect peak temperature evolution in friction stir welding (FSW). This work develops a semi-empirical model for peak temperature estimation during FSW of aluminium alloys. Several bead-on-plate runs were conducted on AA5083-H111, AA6082-T6 and AA7075-T6. Different rotational and welding speeds were tested while measuring the temperature with a thermocouple embedded in the tool. A polynomial model was proposed with the model's coefficients strongly correlating to the material thermal properties. Additionally, a threshold peak temperature was defined to avoid cold defects by combining temperature measurements with joint quality information obtained from X-ray scans. The efficiency of the model and the defined threshold are proven by applying them to the literature.
Actomyosin fibers DApPLE epithelial apical junctions
Authors: Manzano Alejandra R. , Martín-Belmonte Fernando
Published: April 2022

Epithelial cell morphology is essential for cellular homeostasis, but the mechanisms by which cell shape is established remain unclear. In this study, Marivin et al. (2022. J. Cell Biol.https://doi.org/10.1083/jcb.202111002) identify DAPLE as a linker between polarity complexes and the actomyosin network at apical junctions. By recruiting CD2P and activating Gαβγ-mediated RhoA signaling, DAPLE ensures proper cell shape and function.
Life-threatening viral disease in a novel form of autosomal recessive IFNAR2 deficiency in the Arctic
Authors: Duncan Christopher J.A. , Skouboe Morten K. , Howarth Sophie , Hollensen Anne K. , Chen Rui , Børresen Malene L. , Thompson Benjamin J. , Stremenova Spegarova Jarmila , Hatton Catherine F. , Stæger Frederik F. , Andersen Mette K. , Whittaker John , Paludan Søren R. , Jørgensen Sofie E. , Thomsen Martin K. , Mikkelsen Jacob G. , Heilmann Carsten , Buhas Daniela , Øbro Nina F. , Bay Jakob T. , Marquart Hanne V. , de la Morena M. Teresa , Klejka Joseph A. , Hirschfeld Matthew , Borgwardt Line , Forss Isabel , Masmas Tania , Poulsen Anja , Noya Francisco , Rouleau Guy , Hansen Torben , Zhou Sirui , Albrechtsen Anders , Alizadehfar Reza , Allenspach Eric J. , Hambleton Sophie , Mogensen Trine H.
Published: April 2022

Type I interferons (IFN-I) play a critical role in human antiviral immunity, as demonstrated by the exceptionally rare deleterious variants of IFNAR1 or IFNAR2. We investigated five children from Greenland, Canada, and Alaska presenting with viral diseases, including life-threatening COVID-19 or influenza, in addition to meningoencephalitis and/or hemophagocytic lymphohistiocytosis following live-attenuated viral vaccination. The affected individuals bore the same homozygous IFNAR2 c.157T>C, p.Ser53Pro missense variant. Although absent from reference databases, p.Ser53Pro occurred with a minor allele frequency of 0.034 in their Inuit ancestry. The serine to proline substitution prevented cell surface expression of IFNAR2 protein, small amounts of which persisted intracellularly in an aberrantly glycosylated state. Cells exclusively expressing the p.Ser53Pro variant lacked responses to recombinant IFN-I and displayed heightened vulnerability to multiple viruses in vitro—a phenotype rescued by wild-type IFNAR2 complementation. This novel form of autosomal recessive IFNAR2 deficiency reinforces the essential role of IFN-I in viral immunity. Further studies are warranted to assess the need for population screening.
Non-gravitational force measurement and correction by a precision inertial sensor of TianQin-1 satellite
Authors: Zhou An-Nan , Cai Lin , Xiao Chun-Yu , Tan Ding-Yin , Li Hong-Yin , Bai Yan-Zheng , Zhou Ze-Bing , Luo Jun
Published: April 2022

Non-gravitational force models are critical not only for the applications of satellite orbit determination and prediction, but also for the studies of gravitational reference sensors in space-based gravitational wave detection missions and accelerometers in gravity satellite missions. In this paper, based on the inertial sensor data from the TianQin-1 (TQ-1) mission, a correction has been made in the non-gravitational force models by applying additional terms related to the orbital periods. After taking into account this correction, about 37 hours of TQ-1 inertial sensor data is calibrated in the sensitive axes, i.e. y- and z-axes, by comparing with the simulated non-gravitational accelerations. It is indicated that the peak-to-peak value of the non-gravitational acceleration correction terms are about 2% and 13% of the measured accelerations in the y- and z-axes, respectively. Within the frequency band below 0.01 Hz, the root mean square of calibration residual errors in y- and z-axes are suppressed from 1.03 × 10−9 and 3.872 × 10−9 m s−2 to 8.14 × 10−10 and 1.343 × 10−9 m s−2, respectively. The bias and scale factor of the inertial sensor are also obtained from the calibration by the method of least-squares fit. Meanwhile, the inertial sensor measurements are validated and their signal compositions are analyzed.
Development of 4D-printed shape memory polymer large-stroke XY micropositioning stages
Authors: Cheah Dik Son , Alshebly Yousif Saad , Mohamed Ali Mohamed Sultan , Nafea Marwan
Published: April 2022

This paper presents two novel large-stroke XY micropositioning stages that are fabricated completely using four-dimensional (4D) printed polylactic acid (PLA). The proposed designs do not require manual training to perform actuation. Instead, printing speed is used to achieve shape programming and manipulate the deformation and shrinking levels of the PLA microactuators that control the microstage. A relationship between the printing speed, number of layers, and deformation value is formulated to model the performance of the microactuators based on these variables. The same approach is then used to develop the two proposed designs in this work. One-way actuations in the x- and y-axes are achieved using PLA actuators that are printed at speeds in the range of 40–80 mm s−1, while the rest of the structure (passive part) is printed at a speed of 10 mm s−1 to minimize unwanted deformations. The microactuators are activated by immersing the designs in hot water at 85 °C. The maximum values of the x- and y-actuations are achieved when using the highest printing speed for the microactuators. Design 1 offers actuation values of 1.99 and 1.40 mm along the x- and y-axes, respectively, while these values are 1.76 and 2.30 mm when using Design 2. The proposed designs offer a cost-effective batch fabrication solution for micropositioning applications, where the weight of the PLA required for Design 1 and Design 2 is 48.37 g and 12.61 g, respectively, which respectively costs $0.65 and $0.17. The performance of the x- and y-axes actuations show repeatable results with standard deviation values of 0.062 and 0.050 for Designs 1, and 0.054 and 0.047 for Design 2, respectively. Moreover, the standard deviation of the reproducibility of the x- and y-axes actuations are 0.064 and 0.051 for Designs 1, and 0.054 and 0.048 for Design 2, respectively. In addition, the designs offer a promising performance compared to the currently available large-stroke micropositioning stages in terms of the simplicity of the fabrication process and the area ratio.
Vortex lattices in binary Bose–Einstein condensates: collective modes, quantum fluctuations, and intercomponent entanglement
Authors: Yoshino Takumi , Furukawa Shunsuke , Ueda Masahito
Published: April 2022

We study binary Bose–Einstein condensates subject to synthetic magnetic fields in mutually parallel or antiparallel directions. Within the mean-field theory, the two types of fields have been shown to give the same vortex-lattice phase diagram. We develop an improved effective field theory to study properties of collective modes and ground-state intercomponent entanglement. Here, we point out the need to introduce renormalized coupling constants for coarse-grained densities. We show that the low-energy excitation spectra for the two types of fields are related to each other by suitable rescaling with the renormalized coupling constants. By calculating the entanglement entropy, we find that for an intercomponent repulsion (attraction), the two components are more strongly entangled in the case of parallel (antiparallel) fields, in qualitative agreement with recent studies for a quantum (spin) Hall regime. We also find that the entanglement spectrum exhibits an anomalous square-root dispersion relation, which leads to a subleading logarithmic term in the entanglement entropy. All of these are confirmed by numerical calculations based on the Bogoliubov theory with the lowest-Landau-level approximation. Finally, we investigate the effects of quantum fluctuations on the phase diagrams by calculating the correction to the ground-state energy due to zero-point fluctuations in the Bogoliubov theory. We find that the boundaries between rhombic-, square-, and rectangular-lattice phases shift appreciably with a decrease in the filling factor.
Helicity dependent Wigner phase shift for photoionization in a circularly polarized laser field
Authors: Wang Run , Zhang Qingbin , Cao Chuanpeng , Li Min , Liu Kunlong , Lu Peixiang
Published: April 2022

The sensitivity of strong-field ionization to atomic orbital helicity has attracted much attention from physicists, due to its potential application in attosecond spectroscopy and spintronics. In order to intuitively observe the physical mechanisms of helicity-dependent ionization rates during photoionization, the concept of the Wigner phase can be used to characterize the different interactions between the rotating electrons and the Coulomb potential. Here, we find that in both one- and three-photon ionization schemes, the electrons liberated more easily by the circularly polarized laser field suffer less influence of the Coulomb potential during the propagation and then accumulate less Winger phase. This result indicates that the strength of the interaction between the rotating electrons and the Coulomb potential can explain the helicity-dependent ionization for different ionization mechanisms universally, which is also supported by our classical ensemble analysis. Our work provides an intuitive perspective towards the physics picture of ionization propensity rules.
Ionization by electron impacts and ionization potential depression
Authors: Benredjem Djamel , Pain Jean-Christophe , Calisti Annette , Ferri Sandrine
Published: April 2022

We calculate the cross-section of ionization by free-electron impacts in high or moderate density plasmas. We show that the so-called ionization potential depression (IPD) strongly affects the magnitude of the cross-section in the high-density domain. We use the well-known IPD formulas of Stewart–Pyatt and Ecker–Kröll. A more recent approach based on classical molecular dynamics simulation is also investigated. The latter provides an alternative way to calculate IPD values. At near-solid densities the effects of the free-electron degeneracy should be investigated. The rates are then calculated within the Fermi–Dirac statistics. We first use the semi-empirical formula of Lotz for ionization cross-section. The results may differ significantly from measured cross-sections or calculations with reliable atomic codes. Then, in a second step, we propose a new formula that combines the Lotz formula and a polynomial expansion in terms of the ratio of the energy of the incident electron and the ionization energy. The coefficients of the polynomial expansion are adjusted to fit the cross-section provided by robust atomic codes. A great advantage of the new formula is that it allows a fully analytical calculation of the ionization rate. Our results are compared to experiments measuring IPDs, cross-sections and rate coefficients on aluminum at high and moderate densities and on Be-like CNO ions.
CASPPNet: a chained atrous spatial pyramid pooling network for steel defect detection
Authors: Zheng Zhouzhou , Hu Yaohua , Zhang Yan , Yang Huanbo , Qiao Yichen , Qu Zhanghao , Huang Yuxiang
Published: April 2022

Automatic machine vision-based defect detection has been successfully applied to many industrial visual inspection applications. However, automatic steel surface defect detection is still a challenging task due to diverse defect categories, low-contrast between defect and complex texture background. To address these challenges, a chained atrous spatial pyramid pooling network (CASPPNet) is proposed for steel surface defect detection. In CASPPNet, chained atrous spatial pyramid pooling is designed to enlarge receptive field and obtain enrich semantic information. An improved global attention feature fusion module is introduced to achieve feature interaction and salience. Moreover, residual boundary refinement block is introduced to get more complete defect boundary. Comparative experimental results verify that our method is superior to the state-of-the-art segmentation methods on public accessible SD-saliency-900 datasets and can meet the requirement of real-time online detection (the detection efficiency is at over 47 FPS on a single GPU).
Magnetohydrodynamic dynamo effect from electrostatic drift velocity field on sustainment of reversed field pinch plasmas in three-dimensional KTX equilibrium
Authors: Zu Yiming , Mao Wenzhe , Liu Jinmao , Liu Haifeng , Zhang Shoubiao , Lan Tao , Li Hong , Xie Jinlin , Liu Adi , Zhou Chu , Xu Yuhong , Ding Weixing , Zhuang Ge , Liu Wandong
Published: April 2022

A dynamo is necessary for reversed field pinch (RFP) configuration sustainment in a continuous way or oscillation cycles by self-organization. A dynamo velocity field from electrostatic drift is studied in three-dimensional (3D) equilibrium for Keda Torus eXperiment RFP plasmas in quasi-multi-helical (QMH) and quasi-single-helical (QSH) states. The 3D equilibrium reconstruction is computed by VMEC code. It is found that the electrostatic potential provides helical modulation of plasma flow in QSH states. The electrostatic potential in QMH states is processed as a superposition of limited helical harmonics, and it shows an axisymmetric pattern. Non-axisymmetric components are negligible in QMH states because of flux surface averaging of the electrostatic field and corresponding electrostatic drift flow. The electrostatic drift velocity is comparable to the total plasma drift in QSH states; this implies that the electrostatic drift may play an important role in sustaining the helical configuration in RFP plasma.
Mechanical properties of novel folded kirigami metamaterials under quasi-static compression
Authors: Li Bangzheng , Huang Zhixin , Lin Yongshui , Kang Xiao , Li Ying
Published: April 2022

Origami and kirigami are effective approaches to fabricate lightweight cellular metamaterials with extraordinary mechanical properties. However, the novel designs of such metamaterials are still limited. In this paper, a novel metamaterial similar to typical Kelvin foams is proposed and fabricated via origami and kirigami methods, and its mechanical properties are investigated. Quasi-static compression tests are first conducted to analyze the deformation characteristics and stress–strain responses. Numerical simulations are then carried out to simulate the tests. Furthermore, two methods including adjusting the wall thickness and introducing openings are adopted to alter the relative density of the metamaterials, and their influences on the plateau stress and specific energy absorption (SEA) are explored. Finally, analytical studies are conducted to predict the plateau stress, and good agreement between the analytical, numerical, and experimental results are obtained. The results reveal that the kinetic energy is primarily dissipated by unfolding the constitutive elements along the creases, and three typical stages of linear-like elastic, plateau, and densification are generated in the stress–strain curves. Increasing the wall thickness significantly improves the plateau stress and SEA. Introducing smaller openings has minor influences on the plateau stress, while the stress level drops remarkably when the opening size exceeds a critical value. By adopting an appropriate opening size, the increment of the SEA can be up to 29% in comparison with non-opening counterparts. The findings of the present study provide an alternative to fabricating cellular materials with outstanding performance.
Trapped magnetic field distribution above a superconducting linear Halbach array
Authors: Houbart M , Fagnard J-F , Dular J , Dennis A R , Namburi D K , Durrell J H , Geuzaine C , Vanderheyden B , Vanderbemden P
Published: April 2022

In applications requiring a large magnetic force, permanent magnets with non-parallel magnetization directions can be assembled in a Halbach array to generate a large gradient of magnetic flux density. The saturation magnetization of permanent magnets, however, brings a fundamental limit on the performance of this configuration. In the present work, we investigate experimentally the assembly of cuboid bulk, large grain melt-textured YBa2Cu3O

7
−
x

superconductors (

∼

14
×
14
×
14

mm3) with orthogonal c-axes so as to form a basic unit of Halbach array. The experiments are carried out at 77 K. The experimental distribution of the magnetic flux density above the array of trapped-field superconductors is compared to a similar array made of permanent magnets. A simple analytical model is developed and is shown to accurately reproduce the main experimental observations. The results suggest that a redistribution occurs in the current flowing in the central sample when the distance between the superconductors is reduced, whereas the neighbouring superconductors are unaffected. It is shown that this current redistribution yields a reduced contribution of the central sample to the magnetic flux density above the centre of the array and a new negative contribution associated with stray fields to the magnetic flux density at this location. This interpretation is confirmed by modelling of the distribution of transport currents in the superconductor using a 3D finite element model.
Infinitesimal reference frames suffice to determine the asymmetry properties of a quantum system
Authors: Alexander Rhea , Gvirtz-Chen Si , Jennings David
Published: April 2022

Symmetry principles are fundamental in physics, and while they are well understood within Lagrangian mechanics, their impact on quantum channels has a range of open questions. The theory of asymmetry grew out of information-theoretic work on entanglement and quantum reference frames, and allows us to quantify the degree to which a quantum system encodes coordinates of a symmetry group. Recently, a complete set of entropic conditions was found for asymmetry in terms of correlations relative to infinitely many quantum reference frames. However, these conditions are difficult to use in practice and their physical implications unclear. In the present theoretical work, we show that this set of conditions has extensive redundancy, and one can restrict to reference frames forming any closed surface in the state space that has the maximally mixed state in its interior. This in turn implies that asymmetry can be reduced to just a single entropic condition evaluated at the maximally mixed state. Contrary to intuition, this shows that we do not need macroscopic, classical reference frames to determine the asymmetry properties of a quantum system, but instead infinitesimally small frames suffice. Building on this analysis, we provide simple, closed conditions to estimate the minimal depolarization needed to make a given quantum state accessible under channels covariant with any given symmetry group.
Wide-range T
2 resistivity and umklapp scattering in moiré graphene
Authors: Ishizuka Hiroaki , Levitov Leonid
Published: April 2022

We argue that the unusually strong electron–electron interactions in the narrow bands in moiré superlattices originate from compact Wannier orbitals. Enhanced overlaps of electronic wavefunctions, enabled by such orbitals, result in a strong el–el superlattice umklapp scattering. We identify the umklapp scattering processes as a source of the strong temperature-dependent resistivity observed in these systems. In a simple model, the umklapp scattering predicts a T-dependent resistivity that grows as T
2 with a numerical prefactor that grows as the Wannier orbital radius decreases. We quantify the enhancement in el–el scattering by the Kadowaki–Woods (KW) ratio, a quantity that is sensitive to umklapp scattering but, helpfully, insensitive to the effects due to the high density of electronic states. Our analysis predicts anomalously large KW ratio values that clearly indicate the importance of the umklapp el–el processes and their impact on the T-dependent resistivity.
Detection of glucose concentration using a surface plasmon resonance biosensor based on barium titanate layers and molybdenum disulphide sheets
Authors: Almawgani Abdulkarem H M , Taya Sofyan A , Daher Malek G , Colak Ilhami , Wu Feng , Patel Shobhit K
Published: April 2022

Diabetes is rapidly becoming a serious and life-threatening disease. It affects 415 million persons worldwide and is a leading cause of death among those aged 20 to 59. It is essential to develop a rapid-detection, accurate and sensitive glucose detector. In this work, a biosensor based on surface plasmon resonance (SPR) is proposed theoretically for the detection of glucose concentration. To realize higher sensitivity, the proposed SPR sensor contains a barium titanate layer placed between the metal (Ag) thin film and the molybdenum disulphide layer. Barium titanate material shows notable dielectric properties, such as low loss and a high index of refraction. It is expected to give a large shift in the resonance angle caused by a tiny change in the analyte refractive index. By optimizing the thicknesses of barium titanate and Ag and the number of molybdenum disulphide layers, the proposed biosensor can exhibit an ultra-high sensitivity of 307.36 deg RIU−1. The extremely high sensitivity makes the proposed SPR-based biosensor encouraging to be used in many fields of biosensing.
Collimation and monochromaticity of γ-rays generated by high-energy electron colliding with tightly focused circularly polarized laser with varied intensities
Authors: Chang Yifan , Wang Chang , Wang Yubo , Long Zhaonan , Zeng Zirui , Tian Youwei
Published: April 2022

The collision of high-energy electron and laser pulses produces nonlinear inverse Thomson scattering, which can generate γ-rays. We study the effect of laser intensity on the energy angular distribution and spectrum of γ-ray radiation in tightly focused pulses. The γ-rays at non-relativistic intensity have good collimation and monochromaticity, and the radiation energy increases with the laser intensity. The ‘jumping point’ phenomenon of radiation energy variation under relativistic intensity and the ‘black hole’ of energy angular distribution were discovered. As the laser intensity increases, there is a red shift in the radiative harmonic spectrum. And at relativistic intensity, supercontinuum (tunable) γ-rays can be obtained. These findings help us use NITS for optical research.
Observation of V-type electromagnetically induced transparency and optical switch in cold Cs atoms by using nanofiber optical lattice
Authors: Qin Xiateng , Jiang Yuan , Ma Weixin , Ji Zhonghua , Peng Wenxin , Zhao Yanting
Published: April 2022

Optical nanofiber (ONF) is a special tool to achieve the interaction between light and matter with ultralow power. In this paper, we demonstrate V-type electromagnetically induced transparency (EIT) in cold atoms trapped by an ONF-based two-color optical lattice. At an optical depth of 7.35, 90% transmission can be achieved by only 7.7 pW coupling power. The EIT peak and linewidth are investigated as a function of the coupling optical power. By modulating the pW-level control beam of the ONF-EIT system in sequence, we further achieve efficient and high contrast control of the probe transmission, as well as its potential application in the field of quantum communication and quantum information science by using one-dimensional atomic chains.
Numerical investigation of the nonlinear spectral broadening aiming at a few-cycle regime for 10 ps level Nd-doped lasers
Authors: Yang Xi-Hang , Wu Fen-Xiang , Xu Yi , Hu Jia-Bing , Bai Pei-Le , Chen Hai-Dong , Chen Xun , Leng Yu-Xin
Published: April 2022

We present a cascaded nonlinear spectral broadening scheme for Nd-doped lasers, featuring with long pulse duration and high average power. This scheme is based on two multi-pass cells (MPCs) and one multiple-plate supercontinuum generation (MPSG), and the numerical investigation is driven by a home-made Nd-doped fiber laser with 12 ps pulse duration, 50 kHz repetition rate and 100 W average power. The MPC-based first two stages allow us to broaden the pulse spectrum to 4 nm and 43 nm respectively, and subsequently, the MPSG-based third stage allows us to reach 235 nm spectral bandwidth. This broadened spectrum can support a Fourier-transfer-limited pulse duration of 9.8 fs, which is shorter than three optical cycles. To the best of our knowledge, it is the first time to demonstrate the possibility of few-cycle pulses generation based on the 10 ps level Nd-doped lasers. Such few-cycle and high average power laser sources should be attractive and prospective, benefiting from the characteristics of structure compact, low-cost and flexibility.
Defect physics of the quasi-two-dimensional photovoltaic semiconductor GeSe
Authors: Yan Saichao , Wei Jinchen , Wang Shanshan , Huang Menglin , Wu Yu-Ning , Chen Shiyou
Published: April 2022

GeSe has recently emerged as a photovoltaic absorber material due to its attractive optical and electrical properties as well as earth abundancy and low toxicity. However, the efficiency of GeSe thin-film solar cells (TFSCs) is still low compared to the Shockley–Queisser limit. Point defects are believed to play important roles in the electrical and optical properties of GeSe thin films. Here, we perform first-principles calculations to study the defect characteristics of GeSe. Our results demonstrate that no matter under the Ge-rich or Se-rich condition, the Fermi level is always located near the valence band edge, leading to the p-type conductivity of undoped samples. Under Se-rich condition, the Ge vacancy (VGe) has the lowest formation energy, with a (0/2–) charge-state transition level at 0.22 eV above the valence band edge. The high density (above 1017 cm−3) and shallow level of VGe imply that it is the p-type origin of GeSe. Under Se-rich growth condition, Sei has a low formation energy in the neutral state, but it does not introduce any defect level in the band gap, suggesting that it neither contributes to electrical conductivity nor induces non-radiative recombination. In addition, Gei introduces a deep charge-state transition level, making it a possible recombination center. Therefore, we propose that the Se-rich condition should be adopted to fabricate high-efficiency GeSe solar cells.
Spin–orbit coupling adjusting topological superfluid of mass-imbalanced Fermi gas
Authors: Feng Jian , Zhang Wei-Wei , Lin Liang-Wei , Cai Qi-Peng , Zhang Yi-Cai , Ma Sheng-Can , Liu Chao-Fei
Published: April 2022

Topological superfluid state is different from the normal superfluid one due to the excitation energy gap on the boundary. How to obtain the topological superfluid state by using spin–orbit coupling to control the s-waves paired mass-imbalanced Fermi gas is a recent novel topic. In this paper, we study the topological superfluid phase diagram of two-dimensional mass-imbalanced Fermi gas with Rashba spin–orbit coupling at zero temperature. We find that due to the competition among mass imbalance, pairing interaction and spin–orbit coupling, there is a double-well structure in the thermodynamic potential, which affects the properties of the ground state of the system. We comprehensively give the phase diagrams of the system on the plane of spin–orbit coupling and chemical potential, and the phase diagrams on the plane of the reduced mass ratio and two-body binding energy. This study not only points out the stable region of topological superfluid state of mass-imbalanced Fermi gas, but also provides a detailed theoretical basis for better observation of topological superfluid state in experiments.
Femtosecond laser-induced Cu plasma spectra at different laser polarizations and sample temperatures
Authors: Liu Yitong , Wang Qiuyun , Jiang Luyun , Chen Anmin , Han Jianhui , Jin Mingxing
Published: April 2022

Laser-induced breakdown spectroscopy (LIBS) is a good technique for detecting and analyzing material elements due to the plasma emission produced by the high-power laser pulse. Currently, a significant topic of LIBS research is improving the emission intensity of LIBS. This study investigated the effect of laser-polarization on femtosecond laser-ablated Cu plasma spectra at different sample temperatures. The measured lines under circularly polarized lasers were higher than those under linearly and elliptically polarized lasers. The enhancement effect was evident at higher Cu temperatures when comparing the plasma spectra that have circular and linear polarizations for different target temperatures. To understand the influence of laser-polarization and sample temperature on signal intensity, we calculated the plasma temperature (PT) and electron density (ED) . The change in PT and ED was consistent with the change in the atomic lines as the laser polarization was being adjusted. When raising the Cu temperature, the PT increased while the ED decreased. Raising the Cu temperature whilst adjusting the laser-polarization is effective for improving the signal of femtosecond LIBS compared to raising the initial sample temperature alone or only changing the laser polarization.