bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen and moisture-induced healing of halide double perovskite surface defects
Authors: Bhawna  , Alam Aftab , Aslam M.
Published: August 2023

In this work, we studied the impact of environmental constituents such as oxygen (O2) and moisture on halide double perovskite (HDP) films. The transport measurements indicate that an increment in O2 concentration enhances the resistivity of a Cs2AgBiBr6 film by two orders of magnitude. The adsorption of O2 on the film’s surface helps in passivation of defects (∼50% reduction in defect density on O2 exposure), which inhibits ion migration and results in an increased resistivity of the film. The process of adsorption and desorption of O2 on the film surface is found to be fully reversible. In contrast, the resistivity of double perovskite films decreases by an order of magnitude in the presence of moisture. This is attributed to the generation of free protons as a result of the dissociation of water molecules at the films’ surface, hence exhibiting an increase in current under external bias. The HDP films possess high resistivity (for T < 100 °C) due to the desorption of physisorbed water layers from the surface, which gradually decreases with an increase in the operating temperature. This work demonstrates that O2 and moisture are a good combination for defect passivation in any HDPs, in general.
Tight bounds correlating peak absorption with Q-factor in composites and metallic clusters of particles
Authors: Deshmukh Kshiteej J. , Milton Graeme W.
Published: August 2023

Resonances are fundamentally important in the field of nano-photonics and optics. Thus, it is of great interest to know what are the limits to which they can be tuned. The bandwidth of the resonances in materials is an important feature, which is commonly characterized by using the Q-factor. We present tight bounds correlating the peak absorption with the Q-factor of two-phase quasi-static metamaterials and plasmonic resonators evaluated at a given peak frequency by introducing an alternative definition for the Q-factor in terms of the complex effective permittivity of the composite material. This composite may consist of well-separated clusters of plasmonic particles, and, thus, we obtain bounds on the response of a single cluster as governed by the polarizability. Optimal metamaterial microstructure designs achieving points on the bounds are presented. The most interesting optimal microstructure is a limiting case of doubly coated ellipsoids that attains points on the lower bound. We also obtain bounds on Q for three dimensional, isotropic, and fixed volume fraction two-phase quasi-static metamaterials and particle clusters with an isotropic polarizability. Some almost optimal isotropic microstructure geometries are identified.
Particle dynamics in compressible turbulent vertical channel flows
Authors: Li Tingting , Cui Zhiwen , Yuan Xianxu , Zhang Ying , Zhou Qiang , Zhao Lihao
Published: August 2023

In this work, we carry out direct numerical simulations of particle suspensions in the compressible turbulent vertical channel (TVC) flows with Mach number Ma = 1.5 and particle Stokes number St = 1–100. The compressibility effect is considered in the particle dynamic model for the first time in the study of compressible particle-laden wall turbulence. We find that in both incompressible and compressible flow, gravity weakens the wall-normal and spanwise fluctuations of particle velocities as the Stokes number increases. However, compared to the incompressible flow case, the compressible effect amplifies the mean velocity, fluctuations of velocity, and slip velocity of particle in the streamwise direction. The wall-normal and spanwise fluctuations of particle velocities are augmented by the compressible effect in the channel core region. Moreover, in the core region, the effect of fluid compressibility on the wall-normal and spanwise fluctuations of particle velocities attenuates as the Stokes number increases, indicating a competition between the compressible effect and the particle inertia effect. We, furthermore, conduct the quadrant analysis of the local fluctuation velocities of fluid at particle positions and observe preferential distributions in the second and the fourth quadrants at y+ = 12.5–13.5. For compressible TVC flows, the pattern of probability distributions is more elongated, and the percentage is slightly higher in the second and fourth quadrants than that of incompressible flows. This observation implies that more particles locate in the ejection and sweep events in compressible flows than that in incompressible flows, which is anticipated to influence the particle wall-normal transport.
Symmetry-projected cluster mean-field theory applied to spin systems
Authors: Papastathopoulos-Katsaros Athanasios , Henderson Thomas M. , Scuseria Gustavo E.
Published: August 2023

We introduce Sz spin-projection based on cluster mean-field theory and apply it to the ground state of strongly correlated spin systems. In cluster mean-fields, the ground state wavefunction is written as a factorized tensor product of optimized cluster states. In previous work, we have focused on unrestricted cluster mean-field, where each cluster is Sz symmetry adapted. We here remove this restriction by introducing a generalized cluster mean-field (GcMF) theory, where each cluster is allowed to access all Sz sectors, breaking Sz symmetry. In addition, a projection scheme is used to restore global Sz, which gives rise to the Sz spin-projected generalized cluster mean-field (SzGcMF). Both of these extensions contribute to accounting for inter-cluster correlations. We benchmark these methods on the 1D, quasi-2D, and 2D J1 − J2 and XXZ Heisenberg models. Our results indicate that the new methods (GcMF and SzGcMF) provide a qualitative and semi-quantitative description of the Heisenberg lattices in the regimes considered, suggesting them as useful references for further inter-cluster correlations, which are discussed in this work.
Density functional descriptions of interfacial electronic structure
Authors: Liu Zhen-Fei
Published: August 2023

Heterogeneous interfaces are central to many energy-related applications in the nanoscale. From the first-principles electronic structure perspective, one of the outstanding problems is accurately and efficiently calculating how the frontier quasiparticle levels of one component are aligned in energy with those of another at the interface, i.e., the so-called interfacial band alignment or level alignment. The alignment or the energy offset of these frontier levels is phenomenologically associated with the charge-transfer barrier across the interface and therefore dictates the interfacial dynamics. Although many-body perturbation theory provides a formally rigorous framework for computing the interfacial quasiparticle electronic structure, it is often associated with a high computational cost and is limited by its perturbative nature. It is, therefore, of great interest to develop practical alternatives, preferably based on density functional theory (DFT), which is known for its balance between efficiency and accuracy. However, conventional developments of density functionals largely focus on total energies and thermodynamic properties, and the design of functionals aiming for interfacial electronic structure is only emerging recently. This Review is dedicated to a self-contained narrative of the interfacial electronic structure problem and the efforts of the DFT community in tackling it. Since interfaces are closely related to surfaces, we first discuss the key physics behind the surface and interface electronic structure, namely, the image potential and the gap renormalization. This is followed by a review of early examinations of the surface exchange-correlation hole and the exchange-correlation potential, which are central quantities in DFT. Finally, we survey two modern endeavors in functional development that focus on the interfacial electronic structure, namely, the dielectric-dependent hybrids and local hybrids.
Multi-scroll attractor and its broken coexisting attractors in cyclic memristive neural network
Authors: Lai Qiang , Chen Yidan
Published: August 2023

This paper proposes a simple-structured memristive neural network, which incorporates self-connections of memristor synapses alongside both unidirectional and bidirectional connections. Different from other multi-scroll chaotic systems, this network structure has a more concise three-neuron structure. This simple memristive neural network can generate a number of multi-scroll attractors in manageable quantities and shows the characteristics of the coexisting attractors and amplitude control. In particular, when the parameters are changed, the coexisting attractors break up around the center of gravity into two centrosymmetric chaotic attractors. Abundant dynamic behaviors are studied through phase portraits, bifurcation diagrams, Lyapunov exponents, and attraction basins. The feasibility of the system is demonstrated by building a circuit realization platform.
A high-temperature and high-pressure cell for in situ visualization of reaction processes by neutron imaging
Authors: Abe Jun , Matsumoto Yoshihiro , Miyazaki Tsukasa , Noma Takashi
Published: August 2023

This study developed a high-temperature and high-pressure (HTHP) cell for in situ neutron imaging of hydrothermal reactions. The cell’s maximum temperature and pressure were 500 °C and 50 MPa, respectively, and its vessel for observing reactions comprised SUS316 stainless steel. Neutron transmission images were obtained to observe the behavior of sub- and supercritical water and the decomposition of two plastics (polypropylene and polyethylene) at HTHP. The images showed that water’s density and phase changed with temperature and pressure, affecting neutron transmission (and thus image brightness). The plastics began to melt and change shape at 150–200 °C, and they decomposed at 500 °C and 20 MPa. This study provides a basis for future research using the HTHP cell to examine various reactions such as the decomposition of biomass samples, the reforming of heavy oil, and the synthesis of nano-materials using sub- and supercritical water.
Correlations between COVID-19 cases and temperature, air humidity, and social isolating rate with cross wavelet transform and wavelet coherence: Case study of New York and São Paulo cities
Authors: Aparecido Magrini Luciano , Monteiro Aguiar Baroni Mariana Pelissari , Goulart Amari , Cilene Gadotti Marta
Published: August 2023

The COVID-19 pandemic originated in 2019 and has become an endemic disease that we must learn to live with, similar to other strains of influenza. The Organization (WHO) declared on May 5, 2023, in Geneva, Switzerland, the end of the Public Health Emergency of International Concern regarding COVID-19. As vaccines become more widely available and the pandemic appears to be improved, our focus shifts to the challenges we still face. Understanding how external factors like temperature, air humidity, and social isolation impact the spread of the SARS-CoV-2 virus remains a crucial challenge beyond our control. In this study, potential links between the number of COVID-19 cases in São Paulo City (SPC) and New York City (NWC) were explored. Our analysis was carried out utilizing the continuous wavelet transform, alongside other tools such as cross-wavelet transform and wavelet coherence. Based on our findings, there appears to be a correlation between the variables related to low frequencies, which aligns with previous research on the topic. Particularly, our research has revealed a connection between COVID-19 cases and factors such as temperature, air humidity, and social isolation rates. Regarding the latter, our findings indicate that implementing social distancing measures was a wise public policy decision, although the correlation with daily COVID-19 cases requires careful analysis. For this study, we analyzed data from February of 2020, when the first cases were reported in the cities under investigation, SPC and NWC, up until December 31, 2022, by which time the vaccination campaign was well under way.
Evolution of high-density submarine turbidity current and its interaction with a pair of parallel suspended pipes
Authors: Guo Xingsen , Luo Qianyu , Stoesser Thorsten , Hajaali Arthur , Liu Xiaolei
Published: August 2023

The method of large-eddy simulation (LES) coupled with the density transport equation is employed to simulate the evolution of a gravity-driven high-density turbidity current and its interaction with a pair of parallel suspended pipes. The LES method is validated first using data of a non-Boussinesq lock-exchange experiment and satisfying agreement between LES and experiment is achieved. The simulations reveal that a shear region forms between high- and low-density fluids each moving in opposite directions which lead to the generation of a series of vortices and a substantial mixing region. Close to the bottom boundary, low-density fluid is entrained near the head of the high-density turbidity current, forming a thin water cushion that separates the turbidity current's head from the seabed, the so-called hydroplaning effect, thereby reducing the density of the head and bottom friction. The current study suggests that the effect of hydroplaning phenomena leads to high speed and long distance of the turbidity current. Further, LES simulations of a turbidity current impacting a pair of parallel suspended pipes with different streamwise spacings are performed and impact forces are quantified. The turbulent wake generated by high-density fluid bypassing pipe 1 promotes velocity fluctuations leading to increased impact forces on pipe 2 with increasing streamwise spacing up to 8 times the pipeline diameter (8D). The results suggest that the streamwise spacing between two parallel pipes should be less than 2D to minimize hydrodynamic loads on pipe 2.
Relaxational dynamics of the T-number conversion of virus capsids
Authors: Clark Alexander Bryan , Safdari Mohammadamin , Zoorob Selim , Zandi Roya , van der Schoot Paul
Published: August 2023

We extend a recently proposed kinetic theory of virus capsid assembly based on Model A kinetics and study the dynamics of the interconversion of virus capsids of different sizes triggered by a quench, that is, by sudden changes in the solution conditions. The work is inspired by in vitro experiments on functionalized coat proteins of the plant virus cowpea chlorotic mottle virus, which undergo a reversible transition between two different shell sizes (T = 1 and T = 3) upon changing the acidity and salinity of the solution. We find that the relaxation dynamics are governed by two time scales that, in almost all cases, can be identified as two distinct processes. Initially, the monomers and one of the two types of capsids respond to the quench. Subsequently, the monomer concentration remains essentially constant, and the conversion between the two capsid species completes. In the intermediate stages, a long-lived metastable steady state may present itself, where the thermodynamically less stable species predominate. We conclude that a Model A based relaxational model can reasonably describe the early and intermediate stages of the conversion experiments. However, it fails to provide a good representation of the time evolution of the state of assembly of the coat proteins in the very late stages of equilibration when one of the two species disappears from the solution. It appears that explicitly incorporating the nucleation barriers to assembly and disassembly is crucial for an accurate description of the experimental findings, at least under conditions where these barriers are sufficiently large.
Effect of shock tunnel geometry on shockwave and vortex ring formation, propagation, and head on collision
Authors: Bauer Rachel L. , Johnson Emily M. , Douglas Alexander D. , Johnson Catherine E.
Published: August 2023

Vortex ring research primarily focuses on the formation from circular openings. Consequently, the role of tunnel geometry is less understood, despite there being numerous research studies using noncircular shock tunnels. This experimental study investigated shockwaves and vortex rings from different geometry shock tunnels from formation at the tunnel opening to head on collision with another similarly formed vortex ring using schlieren imaging and statistical analysis. The velocity of the incident shockwave was found to be consistent across all four shock tunnel geometries, which include circle, hexagon, square, and triangle of the same cross-sectional area. The velocity was 1.2 ± 0.007 Mach and was independent of the tunnel geometry. However, the velocities of the resulting vortex rings differed between the shapes, with statistical analysis indicating significant differences between the triangle and hexagon vortex velocities compared to the circle. Vortex rings from the square and circle shock tunnels were found to have statistically similar velocities. All vortex rings slowed as they traveled due to corner inversion and air drag. All shock tunnels with corners produce a wobble in the vortex rings. Vortex rings interact with opposing incident shockwaves prior to colliding with each other. Vortex velocity before and after shock–vortex interaction was measured and evaluated, showing statistically similar results. Shock–vortex interaction slows the shockwave upon interaction, while the shock–shock interaction resulted in no change in shock velocity. Although the vortex rings travel at different velocities, all head-on vortex ring collisions produce a perpendicular shockwave that travels at 1.04 ± 0.005 Mach.
Converging high-level coupled-cluster energetics via adaptive selection of excitation manifolds driven by moment expansions
Authors: Gururangan Karthik , Piecuch Piotr
Published: August 2023

A novel approach to rapidly converging high-level coupled-cluster (CC) energetics in an automated fashion is proposed. The key idea is an adaptive selection of excitation manifolds defining higher--than--two-body components of the cluster operator inspired by CC(P;Q) moment expansions. The usefulness of the resulting methodology is illustrated by molecular examples where the goal is to recover the electronic energies obtained using the CC method with a full treatment of singly, doubly, and triply excited clusters (CCSDT) when the noniterative triples corrections to CCSD fail.
Machine-learning data-driven modeling of laminar-turbulent transition in compressor cascade
Authors: Li Zhen , Ju Yaping , Zhang Chuhua
Published: August 2023

Laminar-turbulent transition plays a critical role in the aerodynamics of axial-flow compressor cascades. The Reynolds-averaged Navier–Stokes method is so far the most practicable and popular means for numerical simulations of transitional flows to support aerodynamic analysis and the design of compressor cascades. However, the prediction accuracy of the conventional transport equation-based transition models has reached a plateau. In the present work, a machine-learning data-driven transition modeling method that can take full advantage of high-fidelity simulation data is proposed. The turbulence intermittency is calculated algebraically from local flow quantities through a neural network. The proposed method is then applied to construct an algebraic transition model, which is tailored for compressor cascades and coupled with the Spalart–Allmaras turbulence model. The validation results show that the constructed transition model is able to predict flows in compressor cascades with transition in both the Kelvin–Helmholtz instability-induced and bypass modes. Furthermore, the constructed transition model exhibits higher prediction accuracy for both the transition modes than the conventional intermittency factor equation-based transition model. This work demonstrates the effectiveness and promising prospect of machine-learning and data-driven methods in the modeling of complex flow physics.
Phase fraction of ferroelectric Hf0.5Zr0.5O2 film regulated by the co-action of Ce doping and oxygen defects: First principles study
Authors: Tian Yushui , Zhou Yulu , Zhao Miao , Ouyang Yifang , Tao Xiaoma
Published: August 2023

In this work, the effects of cerium doping and oxygen defects of ferroelectric Hf0.5Zr0.5O2 (HZO) are systematically studied by first-principles calculations. According to the results, the combined effect of Ce atoms and oxygen vacancy has a significant effect on the improvement of the orthorhombic phase fraction in HZO, and the mechanism of this phenomenon is also studied. The optimal concentration of Ce doping is 9.375 formula unit%, and the optimal concentration of oxygen vacancy is 9.375 formula unit%. The interaction between Ce doping and oxygen defects is also discussed from the perspective of structural stability and electrical balance. These findings are helpful for the preparation of Ce-doped HZO ferroelectric thin films and provide experience for the study of other dopants.
Miniaturized metachronal magnetic artificial cilia
Authors: Cui Zhiwei , Wang Ye , Zhang Shuaizhong , Wang Tongsheng , den Toonder Jaap M. J.
Published: August 2023

Biological cilia, hairlike organelles on cell surfaces, often exhibit collective wavelike motion known as metachrony, which helps generating fluid flow. Inspired by nature, researchers have developed artificial cilia as microfluidic actuators, exploring several methods to mimic the metachrony. However, reported methods are difficult to miniaturize because they require either control of individual cilia properties or the generation of a complex external magnetic field. We introduce a concept that generates metachronal motion of magnetic artificial cilia (MAC), even though the MAC are all identical, and the applied external magnetic field is uniform. This is achieved by integrating a paramagnetic substructure in the substrate underneath the MAC. Uniquely, we can create both symplectic and antiplectic metachrony by changing the relative positions of MAC and substructure. We demonstrate the flow generation of the two metachronal motions in both high and low Reynolds number conditions. Our research marks a significant milestone by breaking the size limitation barrier in metachronal artificial cilia. This achievement not only showcases the potential of nature-inspired engineering but also opens up a host of exciting opportunities for designing and optimizing microsystems with enhanced fluid manipulation capabilities.
Regularization of electromagnetic field for self-force problem in de Sitter spacetime
Authors: Yaremko Yurij , Duviryak Askold
Published: August 2023

The paper is concerned with the motion of a point electric charge in de Sitter spacetime. A point particle of mass m and charge q moving on a geodesic curve produces electromagnetic field that diverges at a particle’s position. The field is determined by the electromagnetic Green’s function by Higuchi and Lee (2008 Phys. Rev. D 78 084031). The self-force contains both divergent and finite terms, and the latter are responsible for the radiation reaction. Our derivation of an effective equations of motion is based on conservation laws corresponding to the group of isometry of de Sitter space. The Nöther quantities consist of particle’s individual characteristics and energy, momentum, and angular momentum carried by particle’s electromagnetic field. Following the Detweiler–Whiting concept that a charge’s motion should only be enforced by the regular component of its own field, we ignore the divergent terms in conservation laws. We assume that the divergencies are absorbed by particle’s individual characteristics within the renormalization procedure. Finite radiative terms together with kinematic particle’s characteristics constitute ten conserved quantities of closed particle plus field system. Their differential consequences yield the effective equations of motion of radiating charge in an external electromagnetic field and gravitation. Contributions to already renormalized particle’s four-momentum and its inertial mass originated from electromagnetic field and background gravity are also derived from ten balance equations.
Label-free identification of cell death mechanism using scattering-based microscopy and deep learning
Authors: Khoubafarin Somaiyeh , Kharel Ashish , Malla Saloni , Nath Peuli , Irving Richard E , Kaur Devinder , Tiwari Amit K , Ray Aniruddha
Published: August 2023

The detection of cell death and identification of its mechanism underpins many of the biological and medical sciences. A scattering microscopy based method is presented here for quantifying cell motility and identifying cell death in breast cancer cells using a label-free approach. We identify apoptotic and necrotic pathways by analyzing the temporal changes in morphological features of the cells. Moreover, a neural network was trained to identify the cellular morphological changes and classify cell death mechanisms automatically, with an accuracy of over 95%. A pre-trained network was tested on images of cancer cells treated with a different chemotherapeutic drug, which was not used for training, and it correctly identified cell death mechanism with ∼100% accuracy. This automated method will allow for quantification during the incubation steps without the need for additional steps, typically associated with conventional technique like fluorescence microscopy, western blot and ELISA. As a result, this technique will be faster and cost effective.
Formation of reactive chlorine species in Cl− solutions treated by plasma-supplied O atoms and some implications for biological inactivation functions
Authors: Gao Yuting , Liu Zhijie , Pang Bolun , Wang Sitao , Chen Bohan , Qu Zhongping , Zhou Renwu
Published: August 2023

Plasma activated saline solution (PAS) has attracted increased attention in recent years due to wide range of promising applications including sterilization, water treatment, wound healing, and cancer treatment. As we know, reactive oxygen and nitrogen species (RONS) play an important role in plasma applications and its production and action mechanisms have been intensively studied. However, less attention has been paid to the role of reactive chlorine species (RCS). Therefore, researching the mechanism underlying the RCS formation in O-treated saline is necessary to regulate the RCS dose for improving plasma applications. In this work, the concentration of free chlorine (Cl2, HClO, ClO−) are focused to investigate the effect of the addition of Cl− and O2. Results show that the presence of chlorine in solutions, oxygen radicals in plasma jet and the pH of the solution are important factors in the further chemical reactions to RCS. The production of RCS and RONS can be selectively regulated by controlling the three conditions described above. Furthermore, some implications for biological inactivation functions are performed by the A549 lung carcinoma cells to verify the anticancer effects induced by PAS. Schematic of plausible mechanisms of the aqueous chemical processes in solutions are speculated by experimental results. These results provide new insight into the mechanism of chemical activity of PAS, which in turn promotes its more effective biomedical effects.
Ferromagnetic resonators synthesized by metal-organic decomposition epitaxy
Authors: Nguyen Nhat , Herrington Bryce , Chorazewicz Kayetan , (Paul) Wang Szu-Fan , Zielinski Ruthi , Turner John , Ashby Paul D , Kilic Ufuk , Schubert Eva , Schubert Mathias , Parrott Ronald A , Sweet Allen A , Streubel Robert
Published: August 2023

Metal-organic decomposition epitaxy is an economical wet-chemical approach suitable to synthesize high-quality low-spin-damping films for resonator and oscillator applications. This work reports the temperature dependence of ferromagnetic resonances and associated structural and magnetic quantities of yttrium iron garnet nanofilms that coincide with single-crystal values. Despite imperfections originating from wet-chemical deposition and spin coating, the quality factor for out-of-plane and in-plane resonances approaches 600 and 1000, respectively, at room temperature and 40 GHz. These values increase with temperature and are 100 times larger than those offered by commercial devices based on complementary metal-oxide semiconductor voltage-controlled oscillators at comparable production costs.
First principles modeling of mechanical properties of binary alloys containing Ga, Sn, and In for soldering applications
Authors: Mattes Spencer , Brennan Scott , Woodcox Michael
Published: August 2023

Using density functional theory, the elastic properties of various binary Ga, Sn, and In-based alloys have been calculated to determine their viability as potential replacements for toxic Pb-based solders. Computed quantities such as the bulk K, shear G, and Young’s E moduli were used to evaluate the mechanical behavior of the studied materials. The Pugh ratio γ and Poisson’s ratio ν were utilized to quantify the ductility of the alloys. Through comparative charge density analysis, we illustrated the relationship between the relative charge distributions and the aforementioned ductility metrics. Among the 52 studied alloys, 27 were determined to be stable/metastable at room temperature, and each of these stable/metastable materials are expected to be ductile. To facilitate the discovery and implementation of thermodynamically accessible and ductile solders, this work focuses on the mechanical properties of the alloys expected to be stable/metastable. Based on the cutoff criteria for stability and ductility established at the end of this work (

E

F
o
r
m

<

10 meV/atom and γ > 4.00), the α-Ga0.125In0.875, GaII0.750In0.250, GaII0.833Sn0.167 and In0.875Ga0.125 alloys warrant further study for soldering applications.
Correlation effects on topological end-states in finite-size graphene nanoribbons in the GW approximation
Authors: Honet Antoine , Henrard Luc , Meunier Vincent
Published: August 2023

Finite size armchair graphene nanoribbons (GNRs) of different families are theoretically studied using the Hubbard model in both mean-field and GW approximations, including spin correlation effects. It is shown that correlation primarily affect the properties of topological end states of the nanoribbons. A representative structure of each of the three GNR families is considered but the seven-atom width nanoribbon is studied in detail and compared to previously published experimental results, showing a clear improvement when correlations are included. Using isolated spin contributions to scanning tunneling microscopy (STM) simulations, spin-polarized measurements in STM are also suggested to help distinguish and highlight correlation effects.
Design and tactile classification of flexible tactile sensor for soft gripper
Authors: Dong Shuo , Cai Lihua , Wei Yangyang , She Jianguo
Published: August 2023

Tactile object recognition is very important in robot sorting and handling system. The existing researches on tactile recognition mainly focus on rigid grippers, which cannot be directly applied to soft grippers with better safety and applicability. In this paper, a tactile sensor for soft gripper is proposed. The tactile sensor consists of a carbon composite Velostat and a flexible printed circuit designed for soft gripper. The sensor is equipped with signal scanning, amplifying and processing systems. A number of performance tests were carried out on the designed tactile sensor to prove that it has good performance in sensing sensitivity, loading stability, repeatability. In addition, tactile sensors are applied to tactile classification. The two fingers of the flexible gripper were loaded with a sensor and nine different objects were contacted. The tactile information of the objects was obtained through the stable gripper, and the tactile data was trained and classified by the support vector machine. Finally, the tactile recognition accuracy of the double-exponent data was 91.1%.
Rolling bearing fault diagnosis under time-varying speeds based on time-characteristic order spectrum and multi-scale domain adaptation network
Authors: Xu Zhenli , Tang Guiji , Pang Bin , Qi Xiaofan
Published: August 2023

In practical industrial applications, rolling bearing generally operates under variable conditions and its vibration signal significantly fluctuates in amplitude and frequency. This increases the feature distribution differences of the bearing fault samples and makes the health status identification of the bearing more difficult. To this end, a new intelligent fault diagnosis method for bearing under time-varying speed conditions is proposed based on time-characteristic order (TCO) spectrum and multi-scale domain adaptation network (MSDAN). Firstly, by using the good noise robustness and high time–frequency aggregation properties of the synchrosqueezed wave packet transform (SSWPT), the TCO spectrum method based on SSWPT is proposed to eliminate the impact of speed fluctuation, reducing the distribution shift of bearing data under time-varying speeds. Secondly, an MSDAN model based on global-local feature fusion is established to extract the domain-invariant features closely related to the bearing fault state from the TCO spectrum. Finally, the local maximum distribution discrepancy is introduced to capture the discriminative fine-grained features. The feasibility of the proposed method is verified in various transfer tasks on two different bearing datasets with time-varying speeds. Compared with some state-of-art methods, the proposed method can eliminate the sample distribution differences under time-varying speeds, significantly improving its accuracy and generalization performance in cross-domain fault diagnosis of rolling bearing.
Large-area Fe–C eutectic fixed-points for radiation and contact thermometry
Authors: Can Mehtap , Gözönünde Can , Arifoviç Narcisa , Yıldız Fikret , Nasibov Humbat
Published: August 2023

High-quality metal (carbide)–carbon eutectic materials based on high-temperature fixed points (HTFPs) are widely used in radiometry and thermometry as reference standards. HTFPs on the base of iron–carbon (Fe–C) binary eutectic alloys, with a nominal melting temperature of about 1154 °C (just above the copper freezing point of 1084.62 °C), are one of the promising candidates among the eutectic materials. To establish new HTFPs as reference metrological tools for high-temperature thermometry, their performance should be thoroughly investigated regarding reproducibility and stability. In this work, two large-area (8 mm aperture, 107 mm cavity/thermowell length) Fe–C fixed-point cells were constructed and studied in detail using a radiation thermometer and two different thermocouples (TCs). Three different furnaces were used to explore the thermal behaviors of the cells at various furnace gradients and furnace offsets. The melting temperature at the inflections point of the melting curves of the cells studied across extensive measurement campaigns demonstrated good performance with repeatability of less than 9 mK (assessed from four successive runs) and reproducibility—less than 100 mK (at different furnaces and furnace offsets). The melting temperature agreement between both cells in the same experimental conditions was better than 30 mK. In addition, the equivalence of the developed large-area cells and a small-area radiometric cell (3 mm cavity aperture, and 35 mm cavity length) were comparatively examined in the same experimental conditions. The coherence of the obtained results for the melting temperature of large-area Fe–C cells indicates the feasibility of using large-volume cells for precise calibration of both radiation thermometers and TCs.
Students’ contextualizing knowledge on the mirage incident, reflection and refraction: a case study
Authors: Doğru M Said , Kurnaz M Altan
Published: August 2023

The purpose of this study is to examine how high school students apply optical principles and relate them to contexts where reflection, refraction, and dispersion occur together. The study group consists of 60 students enrolled in a high school in the Western Black Sea Region. The data consists of progressive (multiple-choice and open-ended) questions that direct students to specific contexts in which they can explain optical principles. The questions aim to determine students’ contextual and contextualized knowledge. The analysis of the data was carried out by making classifications. The findings are that about half of the students correctly associate the events of ‘reflection’, ‘refraction’ and ‘mirage’ with the given contexts and about three quarters of them cannot define the relevant concepts in the context. According to the findings, it was concluded that the contextual knowledge of the students about the concepts given was partially, but their contextualized knowledge was not sufficient. It is recommended to associate the subjects including the concepts of reflection, refraction and mirage with daily events in order to make them concrete and fun for students in the teaching process, to use up-to-date topics that may attract students ‘attention, and to diversify and increase the contexts appropriate to students’ levels. In addition, it is recommended to make sense of the concept in context in addition to context-concept association in teaching processes.
Saline bolus for negative contrast perfusion imaging in magnetic particle imaging
Authors: Mohn Fabian , Exner Miriam , Szwargulski Patryk , Möddel Martin , Knopp Tobias , Graeser Matthias
Published: August 2023

Objective. Magnetic particle imaging (MPI) is capable of high temporal resolution measurements of the spatial distribution of magnetic nanoparticles and therefore well suited for perfusion imaging, which is an important tool in medical diagnosis. Perfusion imaging in MPI usually requires a fresh bolus of tracer material to capture the key signal dynamics. Here, we propose a method to decouple the imaging sequence from the injection of additional tracer material, without further increasing the administered iron dose in the body with each image. Approach. A bolus of physiological saline solution without any particles (negative contrast) diminishes the steady-state concentration of a long-circulating tracer during passage. This depression in the measured concentration contributes to the required contrast dynamics. The presence of a long-circulating tracer is therefore a prerequisite to obtain the negative contrast. As a quantitative tracer based imaging method, the signal is linear in the tracer concentration for any location that contains nanoparticles and zero in the surrounding tissue which does not provide any intrinsic signal. After tracer injection, the concentration over time (positive contrast) can be utilized to calculate dynamic diagnostic parameters like perfusion parameters in vessels and organs. Every acquired perfusion image thus requires a new bolus of tracer with a sufficiently large iron dose to be visible above the background. Main results. Perfusion parameters are calculated based on the time response of the proposed negative bolus and compared to a positive bolus. Results from phantom experiments show that normalized signals from positive and negative boli are concurrent and deviations of calculated perfusion maps are low. Significance. Our method opens up the possibility to increase the total monitoring time of a future patient by utilizing a positive-negative contrast sequence, while minimizing the iron dose per acquired image.
Mechanical, optoelectronic and thermoelectric properties of lead-free inorganic Li-based double perovskites Li2GeZ6 (Z = Cl, Br, I) for energy applications
Authors: Alburaih Huda A , Nazir Sadia , Laref A
Published: August 2023

In the present work, we investigate lead-free halide DPs Li2GeZ6 (Z = Cl, Br, I) to explore their optoelectronic device applications. The PBEsol functional and modified Becke–Johnson (mBJ) have been brought to determine the lattice constant and band gap, respectively. Calculated formation energies values are found to be −2.48 eV, −2.04 eV, and −1.88 eV for Li2GeCl6, Li2GeBr6, and Li2GeI6, respectively, and all the studied compounds satisfy Born stability criteria for the cubic phase. Band structures computed using mBJ functional yield band gap values of 3.4 eV, 1.8 eV, and 0.4 eV for Li2GeCl6, Li2GeBr6, and Li2GeI6, accordingly, indicating the suitability of these materials for optical devices. The refractive index, absorption, and reflectivity analyses have been evaluated for optical performance in energy ranges from 0–8 eV. Moreover, thermal and electrical conductivities, power factor, and figure-of-merit have been determined under the effect of temperature with the help of the BoltzTrap code. All these aspects, when taken together, provide a comprehensive picture of optical and thermoelectric characteristics and their applications in energy devices.
Anisotropic fluid solution in f (Q) gravity satisfying vanishing complexity factor
Authors: Kaur Simranjeet , Maurya S K , Shukla Sacheendra
Published: August 2023

This paper presents a study on a spherically symmetric anisotropic solution in f(Q) gravity in the framework of vanishing complexity formalism, which derives a relation between gravitational potentials. The Durgapal-Fuloria metric is used to solve the system of equations derived under the linear functional form of f(Q) = β
1
Q + β
2, while the constants are evaluated by joining the interior solution to the Schwarzschild (Anti-) di Sitter exterior solution at the boundary. This study also examines the physical viability and dynamical stability of the solution for the compact star in f(Q)-gravity theory, which shows that the solution found in this study is well-behaved.
Theoretical simulated fabrication of nanostructure by interference of four-beam guided mode excited by 193 nm laser
Authors: Di Xiujuan , Yao Haizi , Wang Xiangxian , Ren Yaqian , Qi Yunping , Yang Hua
Published: August 2023

This study proposed a lithography method for fabricating periodic nanostructures using the interference of four-beam TE0 guided modes excited by a 193 nm deep ultraviolet laser. The physical mechanism and normalized electric field intensity distribution of four-beam TE0 guided mode interference were theoretically analyzed and numerically simulated using the finite element method. The simulation results confirmed the ability of this method to fabricate periodic structures with a half-pitch resolution of 30.35 nm (approximately λ/6.36), an aspect ratio of 3.95, and a contrast ratio of 1. The theoretically calculated value of the resolution was consistent with the numerical simulation value. The resolution and aspect ratio of the fabricated nanostructures could be adjusted through changes to the thickness of the resist. Moreover, the shape of the fabricated nanostructures, such as the one-dimensional sub-wavelength grating structure and two-dimensional square array lattice structure, were adjustable via changes to the number and azimuth of the excited TE0 guided modes. The results obtained in this study provide valuable theoretical information for the practical manufacture of ultra-high-resolution lithography.
Mechanical and corrosion characteristics of micro-arc oxidized magnesium alloy (ZE41) friction stir welds in modified SBF
Authors: Sivashanmugam N , Harikrishna KL , Rao S R Koteswara , Justin S J Samuel , Wilson P
Published: August 2023

Magnesium is a popularly known class of biodegradable metallic biomaterials, and it has spent most of its time in corrosion environments that must be validated before it can be used in real bio applications. This work studies the adaptability of rare earth magnesium alloy (Mg-RE) ZE41 welds for in vitro bio applications. Magnesium rare earth ZE41 alloy plates were welded through a friction stir joining process. The fabrication of a defect-free and strong friction stir butt joint was confirmed by microscopic analysis and mechanical tests. The joint efficiency of 79.25% was arrived from the tensile test based on ultimate tensile strength (UTS). The microhardness at WN, HAZ and base material were measured as 82, 63, and 70 respectively. A silicate electrolyte-based micro-arc oxidation (MAO) coating process was carried out on base and weld samples to study the corrosion behaviour of uncoated and coated samples in modified simulated body fluid (m-SBF). The average coating thickness of the samples was 40 μm. Then the processed samples were immersed in the m-SBF solution for 0.25 h, 72 h, and 168 h, and the degradation behaviour of all the samples was studied. The surface morphology and compositions were analysed through x-ray diffraction and field emission scanning electron microscopy (FE-SEM) on all the MAO-coated and uncoated bases as well as weld samples. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation (PDP) tests were employed to evaluate the electro-chemical induced corrosion behaviour of the samples. The results revealed that MAO-coated ZE41 welded samples have better corrosion mitigation properties with a corrosion rate of 12.45 mpy after 168 h of immersion than all other counterparts due to the compact oxide layer formation and further apatite mineral phase deposition that helps to delay the surface degradation of friction stir welded ZE41.
Future deceleration due to backreaction in a Universe with multiple inhomogeneous domains
Authors: Halder Ashadul , Pandey Shashank Shekhar , Majumdar A.S.
Published: August 2023

We formulate a model of spacetime with inhomogeneous matter distribution in multiple domains. In the context of the backreaction framework using Buchert's averaging procedure, we evaluate the effect of backreaction due to the inhomogeneities on the late time global evolution of the Universe. Examining the future evolution of this universe, we find that it can transit from the presently accelerating phase to undergo future deceleration. The future deceleration is governed by our model parameters. We constrain the model parameters using observational analysis of the Union 2.1 supernova Ia data employing the Markov Chain Monte Carlo method.
Host group degeneracy in gravitational lensing time delay determination of H
0
Authors: Teodori Luca , Blum Kfir
Published: August 2023

Massive elliptical galaxies, that serve as lenses in gravitational lensing time delay measurements of the Hubble parameter H
0, often reside in a host group.
We consider degeneracies in the modeling of the group halo. When the group effect on imaging can be summarized by its flexion (the next order term beyond shear in the tidal expansion), the posterior likelihood map can develop disjoint local minima, associated with an approximate discrete symmetry of a dominant flexion term. Monte-Carlo Markov Chain (MCMC) algorithms that are not designed to explore a rich posterior landscape can miss some of the minima, introducing systematic bias. We study mock data and demonstrate that the bias in H
0 can exceed 10%, and pulls the inference value of H
0 above its truth value, for a reason that can be traced to the structure of a mismodeled flexion term. MCMC algorithms that are designed to cope with a rich posterior landscape can uncover the structure. If the group is X-ray bright enough, X-ray data may also help to resolve the degeneracy, by pinpointing the group's center of mass. Finally, we show that some implementations in the literature used an inaccurate kinematical prior, mis-modeling the group velocity dispersion by as much as 20%.