bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design, fabrication and application of magnetically actuated micro/nanorobots: a review
Authors: Wang Zhongbao , Xu Zhenjin , Zhu Bin , Zhang Yang , Lin Jiawei , Wu Yigen , Wu Dezhi 
Published: December 2021

Abstract
Magnetically actuated micro/nanorobots are typical micro- and nanoscale artificial devices with favorable attributes of quick response, remote and contactless control, harmless human-machine interaction and high economic efficiency. Under external magnetic actuation strategies, they are capable of achieving elaborate manipulation and navigation in extreme biomedical environments. This review focuses on state-of-the-art progresses in design strategies, fabrication techniques and applications of magnetically actuated micro/nanorobots. Firstly, recent advances of various robot designs, including helical robots, surface walkers, ciliary robots, scaffold robots and biohybrid robots, are discussed separately. Secondly, the main progresses of common fabrication techniques are respectively introduced, and application achievements on these robots in targeted drug delivery, minimally invasive surgery and cell manipulation are also presented. Finally, a short summary is made, and the current challenges and future work for magnetically actuated micro/nanorobots are discussed.
Rare earth doped metal oxide nanoparticles for photocatalysis: a perspective
Authors: Mehtab Amir , Ahmed Jahangeer , Alshehri Saad M , Mao Yuanbing , Ahmad Tokeer 
Published: December 2021

Abstract
Metal oxides are well-known materials that have been considered as the prominent photocatalysts. Photocatalysis is a promising way to address the environmental issues which are caused by fossil fuel the combustion and industrial pollutants. Lot of efforts such as doping of metal oxides with metals, non-metals have been made to enhance their photocatalytic activity. More specifically, in this review we have discussed detailed synthesis procedures of rare earth doped metal oxides performed in the past decades. The advantage of doping metal oxides with rare earth metals is that they readily combine with functional groups due to the 4f vacant orbitals. Moreover, doping rare earth metals causes absorbance shift to the visible region of the electromagnetic spectrum which results to show prominent photocatalysis in this region. The effect of rare earth doping on different parameters of metal oxides such as band gap and charge carrier recombination rate has been made in great details. In perspective section, we have given a brief description about how researchers can improve the photocatalytic efficiencies of different metal oxides in coming future. The strategies and outcomes outlined in this review are expected to stimulate the search for a whole new set of rare earth doped metal oxides for efficient photocatalytic applications.
Evolution and modulation of Ag filament dynamics within memristive devices based on necklace-like Ag@TiO2 nanowire networks
Authors: Weng Zhengjin , Zhao Zhiwei , Jiang Helong , Fang Yong , Lei Wei , Liu Changsheng 
Published: December 2021

Abstract
Random nanowire networks (NWNs) are regarded as promising memristive materials for applications in information storage, selectors, and neuromorphic computing. The further insight to understand their resistive switching properties and conduction mechanisms is crucial to realize the full potential of random NWNs. Here, a novel planar memristive device based on necklace-like structure Ag@TiO2 NWN is reported, in which a strategy only using water to tailor the TiO2 shell on Ag core for necklace-like core–shell structure is developed to achieve uniform topology connectivity. With analyzing the influence of compliance current on resistive switching characteristics and further tracing evolution trends of resistance state during the repetitive switching cycles, two distinctive evolution trends of low resistance state failure and high resistance state failure are revealed, which bear resemblance to memory loss and consolidation in biological systems. The underlying conduction mechanisms are related to the modulation of the Ag accumulation dynamics inside the filaments at cross-point junctions within conductive paths of NWNs. An optimizing principle is then proposed to design reproducible and reliable threshold switching devices by tuning the NWN density and electrical stimulation. The optimized threshold switching devices have a high ON/OFF ratio of ∼107 with threshold voltage as low as 0.35 V. This work will provide insights into engineering random NWNs for diverse functions by modulating external excitation and optimizing NWN parameters to satisfy specific applications, transforming from neuromorphic systems to threshold switching devices as selectors.
Investigating the n = 1 and n = 2 error fields in W7-X using the newly accelerated FIELDLINES code
Authors: Engels Dion , Lazerson Samuel A , Bykov Victor , Proll Josefine H E 
Published: December 2021

Abstract
No fusion device can be created without some uncertainty; there is always a slight deviation from the geometric specification. These deviations can add up create a deviation of the magnetic field. This deviation is known as the (magnetic) error field. Correcting these error fields is desired as they cause asymmetries in the divertor loads and can thus cause damage to the device if they grow too large. These error fields can be defined by their toroidal (n) and poloidal number (m). The correction of the n = 1 and n = 2 fields in Wendelstein 7-X (W7-X) is investigated in this work. This investigation focuses on field line diffusion to the divertor, a proxy for divertor heat flux. Such work leverages the 25× speedup obtained through the implementation of a new particle-wall collision model. The n = 1 and n = 2 error fields of the as-built coils model of W7-X are corrected by scanning phase and amplitude of the trim and control coils. Reductions in the divertor load asymmetry by factors of four are demonstrated using error field correction. It is found that the as-built coils model has a significantly lower

m

/

n
=
1

/

1

error field than found in experiments (Bozhenkov et al 2018 Nucl. Fusion
59 026004).
Kelvin-Helmholtz instability and induced magnetic reconnection at the Earth’s magnetopause: a 3D simulation based on satellite data
Authors: Faganello M , Sisti M , Califano F , Lavraud B 
Published: December 2021

Abstract
A 3D two-fluid simulation, using plasma parameters as measured by MMS on 8 September 2015, shows the nonlinear development of the Kelvin–Helmholtz instability at the Earth’s magnetopause. It shows extremely rich dynamics, including the development of a complex magnetic topology, vortex merging and secondary instabilities. Vortex induced and mid-latitude magnetic reconnection coexist and produce an asymmetric distribution of magnetic reconnection events. Off-equator reconnection exhibits a predominance of events in the Southern Hemisphere during the early nonlinear phase, as observed by satellites at the dayside magnetopause. The late nonlinear phase shows the development of vortex pairing for all latitudes while secondary Kelvin–Helmholtz instability develops only in the Northern Hemisphere, leading to an enhancement of the occurrence of off-equator reconnection there. Since vortices move tailward while evolving, this suggests that reconnection events in the Northern Hemisphere should dominate at the nightside magnetopause.
The effect of magnetic island on toroidal ion temperature gradient mode instability
Authors: Zhang Guodong , Guo Weixin , Wang Lu 
Published: December 2021

Abstract
In this work, we have investigated the influence of magnetic island (MI) on electrostatic toroidal ion temperature gradient (ITG) mode, where the ions are described by gyro-kinetic equations including MI, and adiabatic approximation is used for electrons. The eigen-equation for short-wavelength toroidal ITG mode in Fourier-ballooning representation is derived, and the corresponding eigenvalue as well as mode structure are solved. Both the flattening effects of MI on plasma pressure and MI-scale

E
⃗

×

B
⃗

shear flow are considered. It is found that when only considering the flattening effects of MI, the ITG mode can be stabilized compared to the case without MI. Meanwhile, the effective toroidal ITG mode drive can be enhanced by including MI-scale

E
⃗

×

B
⃗

flow, which indicates the dominant destabilizing by MI-scale

E
⃗

×

B
⃗

flow over the stabilizing by flattening profile, which results in a higher growth rate than the case without MI. It is also found that the total flow shearing may prevent the ITG turbulence spreading from the X-point of MI but is not strong enough to prevent spreading from the separatrix across the O-point of larger MI via comparison between the flow shearing rate and the linear growth rate. Furthermore, the corresponding width of the lowest-order mode structure in the ballooning angle is slightly widened (narrowed) for the case without (with) MI-scale

E
⃗

×

B
⃗

flow, compared to the case without MI. Moreover, the shifted even symmetry in the ballooning angle is not qualitatively influenced by the presence of MI. The mode structure is radially asymmetric but is symmetric with respect to the phase of MI at the O-point.
Low-energy electron beam generation in inductively coupled plasma via a DC biased grid
Authors: Jung Jiwon , Lee Moo-Young , Hwang Jae-Gu , Lee Moo-Hyun , Kim Min-Seok , Lee Jaewon , Chung Chin-Wook 
Published: December 2021

Abstract
Low-energy electron beam generation using a DC biased grid was investigated in an inductively coupled plasma (ICP). The electron beam was measured in argon gas at various pressures, ICP source powers, and substrate voltages (V
sub). At a low ICP source power (50 W), an electron beam was generated even at small values of V
sub (10 V), however at a high ICP source power (200 W), an electron beam was only generated when a higher voltage (30 V) was applied due to the short sheath thickness on the grid surface. The sheath on the grid surface is an important factor for generating electron beams because low-energy electrons are blocked. If the sheath thickness to small, a high voltage should be applied to generate an electron beam, as accelerate regions cannot exist without the sheath. At high pressure, since electrons experience numerous neutral collisions, a high substrate voltage is needed to generate an electron beam. However, if the applied substrate voltage becomes too high (40 V) at high pressure, high-energy electrons result in secondary plasma under the grid. Therefore, maintaining a low pressure and low ICP source power is important for generating electron beams.
Three-dimensional tomographically reconstructed optical emission profiles of Hall thruster plasmas
Authors: Kim Jinwoo , Lee Dongho , Doh Guentae , Park Sanghoo , Kim Holak , Choe Wonho 
Published: December 2021

Abstract
A diagnostic system was developed for spectrally resolved, three-dimensional tomographic reconstruction of Hall thruster plasmas, and local intensity profiles of Xe I and Xe II emissions were reconstructed. In this diagnostic system, 28 virtual cameras were generated using a single, fixed charge-coupled device camera by rotating the Hall thruster to form a sufficient number of lines of sight. The Phillips–Tikhonov regularization algorithm was used to reconstruct local emission profiles from the line-integrated emission signals. The reconstruction performance was evaluated using both azimuthally symmetric and asymmetric synthetic phantom images including 5% Gaussian white noise, which resulted in a root-mean-square error of the reconstruction within an order of 10−3 even for a 1% difference in the azimuthal intensity distribution. Using the developed system, three-dimensional local profiles of Xe II emission (541.9 nm) from radiative decay of the excited state 5p4(3P2)6p2[3]°5/2 and Xe I emission (881.9 nm) from 5p5(2P°3/2)6p2[5/2]3 were obtained, and two different shapes were found depending on the wavelength and the distance from the thruster exit plane. In particular, a stretched central jet structure was distinctively observed in the Xe II emission profile beyond 10 mm from the thruster exit, while gradual broadening was found in the Xe I emission. Approximately 10% azimuthal nonuniformities were observed in the local Xe I and Xe II intensity profiles in the near-plume region (<10 mm), which could not be quantitatively distinguished by analysis of the frontal photographic image. Three-dimensional Xe I and Xe II intensity profiles were also obtained in the plume region, and the differences in the structures of both emissions were visually confirmed.
Study of ion separation mechanism in the multi-component vacuum arc discharge
Authors: Sun Qiang , Zhou Qianhong , Zhang Hantian , Yang Wei , Dong Ye , Song Mengmeng 
Published: December 2021

Abstract
The separation phenomenon of light and heavy ions was widely observed experimentally in the vacuum arc discharge with multi-component composite cathode. In this work, a two-dimensional axisymmetric multi-fluid model is used to study the separation mechanism in the multi-component composite cathode vacuum arc. The multi-component vacuum arcs are simulated as a whole which includes separate cathode spot jets, the mixing region, and common arc column. The results show that the plasma jets originated from the separate cathode spot mix together to form a common arc column after a certain distance from the cathode. Due to the rapid increase of ion temperature dozens of times in mixing region of cathode spot jet, the effect of pressure gradient becomes far greater than that of the collisions between light and heavy ions. This leads to a shift in the predominant ion motion mechanism from ion–ion collision (single cathode spot jet region) to pressure expansion (the mixing region). Finally, the light ions gain higher velocities under pressure expansion. In addition, the effect of thermal conductivity and viscosity leads to the wider high temperature regions for light ions, thus making a wider distribution of corresponding ion flux. The numerical results are qualitatively consistent with the experimental results. This paper provides an insight into ion separation mechanism in the multi-component vacuum arc.
Transient behavior of drift and ionization in atmospheric pressure nitrogen discharge
Authors: Dhali S K 
Published: December 2021

Abstract
The fluid models are frequently used to describe a non-thermal plasma such as a streamer discharge. The required electron transport data and rate coefficients for the fluid model are parametrized using the local field approximation (LFA) in first order models and the local-mean-energy approximation (LMEA) in second order models. We performed Monte Carlo simulations in Nitrogen gas with step changes in the E/N (reduced electric field) to study the behavior of the transport properties in the transient phase. During the transient phase of the simulation, we extract the instantaneous electron mean energy, which is different from the steady state mean electron energy, and the corresponding transport parameters and rate coefficients. Our results indicate that the mean electron energy is not a suitable parameter for mobility/drift of electrons due to big difference in momentum relaxation and energy relaxation. However, the high energy threshold rates such as ionization show a strong correlation to mean electron energy. In second order models where the energy-balance equation is solved, we suggest that it would rather be appropriate to use the local electric field to find electron drift velocity in gases such as Nitrogen and the local mean electron energy to determine the ionization and excitation rates.
Design and modelling tools for DC HTS cables for the future railway network in France
Authors: Hajiri Gabriel , Berger Kévin , Dorget Rémi , Lévêque Jean , Caron Hervé 
Published: December 2021

Abstract
The use of high-temperature superconducting (HTS) cables in power systems increases the transmission capacity, whereas reducing the volume of the installation. In addition, in high current applications, HTS cables considerably reduce power losses, right-of-ways and total system mass. This paper presents different multi-physics studies to be performed to accurately design the direct current (DC) HTS cables for the future railway network planned by the French company SNCF. The process used to design DC cables for high operating current (between 5 kA and 20 kA at 1750 V) made of commercial (RE)BaCuO tapes is presented. In this design process, the critical current density dependence J
c(B, θ, T) of the superconducting tapes, the thermal properties of the materials used as well as different cable cooling configurations are considered. Finally, we discuss the selection of the appropriate cooling configuration to ensure adequate cooling of the cable.
Spontaneous trail formation in populations of auto-chemotactic walkers
Authors: Mokhtari Zahra , Patterson Robert I A , Höfling Felix 
Published: December 2021

Abstract
We study the formation of trails in populations of self-propelled agents that make oriented deposits of pheromones and also sense such deposits to which they then respond with gradual changes of their direction of motion. Based on extensive off-lattice computer simulations aiming at the scale of insects, e.g. ants, we identify a number of emerging stationary patterns and obtain qualitatively the non-equilibrium state diagram of the model, spanned by the strength of the agent–pheromone interaction and the number density of the population. In particular, we demonstrate the spontaneous formation of persistent, macroscopic trails, and highlight some behaviour that is consistent with a dynamic phase transition. This includes a characterisation of the mass of system-spanning trails as a potential order parameter. We also propose a dynamic model for a few macroscopic observables, including the sub-population size of trail-following agents, which captures the early phase of trail formation.
Quantum batteries at the verge of a phase transition
Authors: Barra Felipe , Hovhannisyan Karen V , Imparato Alberto 
Published: December 2021

Abstract
Starting from the observation that the reduced state of a system strongly coupled to a bath is, in general, an athermal state, we introduce and study a cyclic battery–charger quantum device that is in thermal equilibrium, or in a ground state, during the charge storing stage. The cycle has four stages: the equilibrium storage stage is interrupted by disconnecting the battery from the charger, then work is extracted from the battery, and then the battery is reconnected with the charger; finally, the system is brought back to equilibrium. At no point during the cycle are the battery–charger correlations artificially erased. We study the case where the battery and charger together comprise a spin-1/2 Ising chain, and show that the main characteristics—the extracted energy and the thermodynamic efficiency—can be enhanced by operating the cycle close to the quantum phase transition point. When the battery is just a single spin, we find that the output work and efficiency show a scaling behavior at criticality and derive the corresponding critical exponents. Due to always present correlations between the battery and the charger, operations that are equivalent from the perspective of the battery can entail different energetic costs for switching the battery–charger coupling. This happens only when the coupling term does not commute with the battery’s bare Hamiltonian, and we use this purely quantum leverage to further optimize the performance of the device.
Assessment of weak-coupling approximations on a driven two-level system under dissipation
Authors: Teixeira W S , Semião F L , Tuorila J , Möttönen M 
Published: December 2021

Abstract
The standard weak-coupling approximations associated to open quantum systems have been extensively used in the description of a two-level quantum system, qubit, subjected to relatively weak dissipation compared with the qubit frequency. However, recent progress in the experimental implementations of controlled quantum systems with increased levels of on-demand engineered dissipation has motivated precision studies in parameter regimes that question the validity of the approximations, especially in the presence of time-dependent drive fields. In this paper, we address the precision of weak-coupling approximations by studying a driven qubit through the numerically exact and non-perturbative method known as the stochastic Liouville–von Neumann equation with dissipation. By considering weak drive fields and a cold Ohmic environment with a high cutoff frequency, we use the Markovian Lindblad master equation as a point of comparison for the SLED method and study the influence of the bath-induced energy shift on the qubit dynamics. We also propose a metric that may be used in experiments to map the regime of validity of the Lindblad equation in predicting the steady state of the driven qubit. In addition, we study signatures of the well-known Mollow triplet and observe its meltdown owing to dissipation in an experimentally feasible parameter regime of circuit electrodynamics. Besides shedding light on the practical limitations of the Lindblad equation, we expect our results to inspire future experimental research on engineered open quantum systems, the accurate modeling of which may benefit from non-perturbative methods.
Collimated neutron beam design for TRR thermal column
Authors: Mozafari Vanani M.J. , Kasesaz Y. , Hosseinipanah M. , Akhound A. 
Published: December 2021

Abstract
Tehran Research Reactor (TRR) is the main neutron source in
Iran which can be used for different applications of neutrons such
as neutron radiography and neutron therapy. TRR has a thermal column
which can provide high intensity flux of thermal neutrons for
users. The aim of this study is to design a neutron collimator for
TRR thermal column to produce parallel neutron beam with suitable
intensity of thermal neutrons. To achieve this goal, Monte Carlo
code of MCNX has been used to evaluate different configurations,
geometries and materials of neutron collimator. The results show
that the final selected configuration can provide a uniform thermal
neutron beam with a flux of
1.21E+13 (cm-2·s-1) which is suitable for
many different neutron applications.
Nesting and degeneracy of Mie resonances of dielectric cavities within zero-index materials
Authors: Duan Xueke , Chen Haoxiang , Ma Yun , Qian Zhiyuan , Zhang Qi , Lai Yun , Peng Ruwen , Gong Qihuang , Gu Ying 
Published: December 2021

Abstract
Resonances in optical cavities are used to manipulate light propagation, enhance light–matter interaction, modulate quantum states, and so on. However, the index contrast between the traditional cavities and the host is generally not high, which to some extent limited their performances. By putting dielectric cavities into a host of zero-index materials, index contrast in principle can approach infinity. Here, we analytically deduced Mie resonance conditions at this extreme circumstance. Interestingly, we discovered a so-called resonance nesting effect, in which a set of cavities with different radii can possess the same type of resonance at the same wavelength. We also revealed previously unknown degeneracy between the 2
l
-TM (2
l
-TE) and

2

l
+
1

-TE (

2

l
+
1

-TM) modes for ɛ ≈ 0 (µ ≈ 0) material, and the 2
l
-TM and 2
l
-TE for both ɛ ≈ 0 and µ ≈ 0. Such extraordinary resonance nesting and degeneracy provide additional principles to manipulate cavity behaviors.