bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of defects and surface roughness on the vortex penetration and vortex dynamics in superconductor–insulator–superconductor multilayer structures exposed to RF magnetic fields: numerical simulations within TDGL theory
Authors: Wang Qing-Yu , Xue Cun , Dong Chao , Zhou You-He 
Published: January 2022

Abstract
Vortex penetration and vortex dynamics are significantly important to superconducting devices, for example, the superconducting cavities, since vortex motions will create substantial dissipation. In experiments, different kinds of defects as well as different degrees of surface roughness were observed. By considering these in superconductor–insulator–superconductor (SIS) structures, vortex penetration and vortex dynamics are very complex due to their interactions with defects and the influence of surface roughness, especially for radio-frequency (RF) magnetic fields, which are quite different from ideal defect-free SIS multilayer structures. In this paper, within the Ginzburg–Landau theory, we perform numerical simulations to study the effects of nanoscale defects, surface roughness, and cracks in the coating layer on the vortex penetration and superheating field in Nb3Sn–I–Nb multilayer structures exposed to a quasi-static magnetic field. The validation of the numerical simulations is verified by good consistency with previous theoretical results in ideal defect-free SIS multilayer and single Nb structures. Furthermore, we explore the vortex dynamics and induced voltages in SIS multilayer structures exposed to RF magnetic fields for both ideal defect-free structures and real situations that include surface roughness. Our numerical simulations indicate that, unlike the quasi-static case, the advantage of SIS multilayer structures over a single Nb structure depends on the degree of surface roughness as well as the frequency and amplitude of the RF magnetic field. The results of this paper provide deep insight to evaluate the actual performance-limiting characteristics of next-generation superconducting RF cavities with different proposed candidate materials, which are quite susceptible to nonideal surfaces.
Experimental estimates of the photon background in a potential light-by-light scattering study
Authors: Doyle L , Khademi P , Hilz P , Sävert A , Schäfer G , Schreiber J , Zepf M 
Published: January 2022

Abstract
High power short pulse lasers provide a promising route to study the strong field effects of the quantum vacuum, for example by direct photon–photon scattering in the all-optical regime. Theoretical predictions based on realistic laser parameters achievable today or in the near future predict scattering of a few photons with colliding Petawatt laser pulses, requiring single photon sensitive detection schemes and very good spatio-temporal filtering and background suppression. In this article, we present experimental investigations of this photon background by employing only a single high power laser pulse tightly focused in residual gas of a vacuum chamber. The focal region was imaged onto a single-photon sensitive, time gated camera. As no detectable quantum vacuum signature was expected in our case, the setup allowed for characterization and first mitigation of background contributions. For the setup employed, scattering off surfaces of imperfect optics dominated below residual gas pressures of 1 × 10−4 mbar. Extrapolation of the findings to intensities relevant for photon–photon scattering studies is discussed.
Analysis of hydrogen fueling, recycling, and confinement at Wendelstein 7-X via a single-reservoir particle balance
Authors: Kremeyer Thierry , König R. , Brezinsek S. , Schmitz O. , Feng Y. , Winters V. , Rudischhauser L. , Buttenschön B. , Brunner K.J. , Drewelow P. , Flom E. , Fuchert G. , Gao Y. , Geiger J. , Jakubowski M. , Killer C. , Knauer J. , Krychowiak M. , Lazerson S. , Reimold F. , Schlisio G. , Viebke H. , the W7-X Team  
Published: January 2022

Abstract
A single-reservoir particle balance for the main plasma species hydrogen has been established for W7-X. This has enabled the quantitative characterization of the particle sources in the standard island divertor configuration for the first time. Findings from attached scenarios with two different island sizes with a boronized wall and turbo molecular pumping are presented. Fueling efficiencies, particle flows and source locations were measured and used to infer the total particle confinement time τ
p. Perturbative gas injection experiments served to measure the effective particle confinement time

τ

p

*

. Combining both confinement times provides access to the global recycling coefficient

R

¯

. Hydrogen particle inventories have been addressed and the knowledge of particle sources and sinks reveals the core fueling distribution and provides insight into the capability of the magnetic islands to control exhaust features. Measurements of hydrogen fueling efficiencies were sensitive to the precise fueling location and measured between 12% and 31% with the recycling fueling at the strike line modeled at only 6%, due to much higher densities. 15% of the total 5.2 × 1022 a/s recycling flow ionizes far away from the recycling surfaces in the main chamber. It was shown that 60% of recycled particles ionize above the horizontal and 18% above the vertical divertor target, while the remainder of the recycling flow ionizes above the baffle (7%). Combining these source terms with their individual fueling efficiencies resolves the core fueling distribution. Due to the higher fueling efficiency in the main chamber, up to 51% of the total 5.1 × 1021 s−1 core fueling particles are entering the confined plasma from the main chamber. τ
p values in the range of 260 ms were extracted for these discharges. Together with τ
p, the global recycling coefficient

R

¯

was resolved for every

τ

p

*

measurement and a typical value close to unity was obtained. An increase of the island size, resulted in no change of τ
p, but doubled

τ

p

*

, indicating the feasibility of the control coils as an actuator to control exhaust features without affecting core confinement properties.
Influence of low-Z impurity on the stabilization of m/n
= 2/1 tearing/locked modes in EAST
Authors: Xu Ming , Liang Yunfeng , Wei Lai , Duan Yanmin , Shi Tonghui , Zhao Hailin , Xu Liqing , Zhou Ruijie , Zhang Ling , Gu Shuai , Gao Wei , Zhang Yang , Wang Zhengxiong , Zang Qing , Liu Haiqing , Sun Youwen , Zhang Shoubiao , Hu Liqun , Gong Xianzu , Xu Guosheng , Hu Jiansen , Wan Baonian , the EAST Team  
Published: January 2022

Abstract
The impact of the low-Z impurity concentration on mode stabilization has been investigated in the EAST tokamak. A series of tearing modes (TMs) with multiple helicities are excited by the low-Z (carbon) impurity concentration, and the dominant mode structure features m/n = 2/1 magnetic islands that propagate in the electron diamagnetic drift direction (m and n are poloidal and toroidal mode numbers, respectively). The m/n = 2/1 locked modes (LMs) can be formed by the redistribution of low-Z impurity concentration, and are unlocked spontaneously due to the decrease in the impurity concentration, where the width of the magnetic islands can reach w ≈ 5 cm (w/a ≈ 0.1, a is the minor radius). The increase in the electromagnetic brake torque is the primary reason for the mode locking, and the ‘O’-point of the m/n = 2/1 magnetic islands is locked by the tungsten protector limiter (toroidal position: −0.4π ⩽ ϕ ⩽ −0.3π) with separation of Δϕ ≈ 0. The 3D asymmetric structure of the m/n = 2/1 magnetic islands is formed for the interaction with the tungsten protector limiter, and the electromagnetic interaction decreases dramatically for the separation of Δϕ ⩾ 0.2π. The mode excitation and locking mechanisms can be illustrated by the ‘hysteresis effect’ between the low-Z impurity concentration and the width of the m/n = 2/1 magnetic islands; namely, the growth of magnetic islands is modulated by the low-Z impurity concentration, and the rotation velocity is decelerated accordingly. However, the intrinsic mechanism for the unlocking of m/n = 2/1 LMs is complicated by considering the concentration of the low-Z impurity, and the possible unlocking mechanism is discussed. Therefore, understanding the relationship between the impurities and magnetic islands is more important for optimization of the control techniques (resonant magnetic perturbations → LMs, electron cyclotron resonant heating (ECRH) → neoclassical tearing mode (NTM), impurity seeding → major collapse, etc).
Evaluation of ambipolar potential barrier in the gas dynamic trap by Doppler spectroscopy
Authors: Lizunov Andrej , Maximov Vladimir , Sandomirsky Andrey 
Published: January 2022

Abstract
The recently developed Doppler spectroscopy diagnostic has been used to evaluate the height of the ambipolar potential barrier forming in the gas dynamic trap (GDT) plasma between the central cell and the region with a large magnetic expansion ratio beyond the mirror. The diagnostic technique based on the gas jet charge exchange target, allowed to measure the potential profile along the line of sight covering the radial range from the axis to the limiter. The on-axis potential drop was found to be 2.6 ÷ 3.1 in units of the central plane electron temperature, which supports the existing theoretical understanding of suppression of electron thermal conductivity in the GDT expander.
Effects of homophily and heterophily on preferred-degree networks: mean-field analysis and overwhelming transition
Authors: Li Xiang , Mobilia Mauro , Rucklidge Alastair M , Zia R K P 
Published: January 2022

Abstract
We investigate the long-time properties of a dynamic, out-of-equilibrium network of individuals holding one of two opinions in a population consisting of two communities of different sizes. Here, while the agents’ opinions are fixed, they have a preferred degree which leads them to endlessly create and delete links. Our evolving network is shaped by homophily/heterophily, a form of social interaction by which individuals tend to establish links with others having similar/dissimilar opinions. Using Monte Carlo simulations and a detailed mean-field analysis, we investigate how the sizes of the communities and the degree of homophily/heterophily affect the network structure. In particular, we show that when the network is subject to enough heterophily, an ‘overwhelming transition’ occurs: individuals of the smaller community are overwhelmed by links from the larger group, and their mean degree greatly exceeds the preferred degree. This and related phenomena are characterized by the network’s total and joint degree distributions, as well as the fraction of links across both communities and that of agents having fewer edges than the preferred degree. We use our mean-field theory to discuss the network’s polarization when the group sizes and level of homophily vary.
Comment on ‘Out-of-equilibrium Frenkel–Kontorova model’ (Imparato A 2021 J. Stat. Mech.
013214)
Authors: Quapp W , Bofill J M 
Published: January 2022

Abstract
We explain the ‘phases’ of a Frenkel–Kontorova chain of atoms in a different way to the commented article. We reject the decision of states of the chain into commensurate and incommensurate states introduced by Aubry.
Steady-state thermodynamics for population dynamics in fluctuating environments with side information
Authors: Miyahara Hideyuki 
Published: January 2022

Abstract
Steady-state thermodynamics (SST) is a relatively newly emerging subfield of physics, which deals with transitions between steady states. In this paper, we find an SST-like structure in population dynamics of organisms that can sense their fluctuating environments. As heat is divided into two parts in SST, we decompose population growth into two parts: housekeeping growth and excess growth. Then, we derive the Clausius equality and inequality for excess growth. Using numerical simulations, we demonstrate how the Clausius inequality behaves depending on the magnitude of noise and strategies that organisms employ. Finally, we discuss the novelty of our findings and compare them with a previous study.
A 25 Gbps VCSEL driving ASIC: an attempt for ultra-high-speed front-end readout applications
Authors: Zhao C. , Guo D. , Chen Q. , Fang N. , Gan Y. , Guo Z. , Sun X. , Yi L. 
Published: January 2022

Abstract
This paper presents the design and the test results of a 25 Gbps VCSEL driving ASIC fabricated in a 55 nm CMOS technology as an attempt for the future very high-speed optical links. The VCSEL driving ASIC is composed of an input equalizer stage, a pre-driver stage and a novel output driver stage. To achieve high bandwidth, the pre-driver stage combines the inductor-shared peaking structure and the active-feedback technique. A novel output driver stage uses the pseudo differential CML driver structure and the adjustable FFE pre-emphasis technique to improve the bandwidth. This VCSEL driver has been integrated in a customized optical module with a VCSEL array. Both the electrical function and optical performance have been fully evaluated. The output optical eye diagram has passed the eye mask test at the data rate of 25 Gbps. The peak-to-peak jitter of 25 Gbps optical eye is 19.5 ps and the RMS jitter is 2.9 ps.
Design of MIRA, a low-noise pixelated ASIC for the readout of micro-channel plates
Authors: Fabbrica E. , Carminati M. , Butta D. , Uslenghi M. , Fiorini M. , Corso A.J. , Pelizzo M.G. , Fiorini C. 
Published: January 2022

Abstract
We present the design of the first prototype of MIRA (MIcro-channel plate Readout ASIC) that has been designed to read out Micro-Channel Plates (MCP), in particular for UV spectroscopy. MIRA will be able to detect the cloud of electrons generated by each photon interacting with the MCP, sustaining high local and global count rates to fully exploit the MCP intrinsic dynamic range with low dead time. The main rationale that guided the electronics design is the reduction of the input Equivalent Noise Charge (ENC) in order to allow operations with lower MCP gain, thus improving its lifetime, crucial aspect for long missions in space. MIRA features two selectable analog processing times, 133 ns or 280 ns (i.e. fast mode or slow mode), granting a count rate per pixel of 100 kcps. Moreover, it shows an Equivalent Noise Charge ENC

=
17

e

r
m
s

−

. A spatial resolution of 35 μm and an operation with zero dead time, due to the readout, are targeted. The low noise, high count rate and high spatial resolution requirements are expected by keeping a compact pixel size (35 μm × 35 μm) for a total of 32 × 32 pixels in a 2 mm × 2 mm ASIC area. In this work, the ASIC design is described.
Environmental concentrations as ratios of random variables
Authors: Perri Saverio , Porporato Amilcare 
Published: January 2022

Abstract
Human-induced environmental change increasingly threatens the stability of socio-ecological systems. Careful statistical characterization of environmental concentrations is critical to quantify and predict the consequences of such changes on human and ecosystems conditions. However, while concentrations are naturally defined as the ratio between solute mass and solvent volume, they have rarely been treated as such, typically limiting the analysis to familiar distributions generically used for any other environmental variable. To address this gap, we propose a more general framework that leverages their definition explicitly as ratios of random variables. We show that the resulting models accurately describe the behavior of nitrate plus nitrite in US rivers and salt concentration in estuaries in the Everglades by accounting for heavy tails potentially emerging when the water volume fluctuates around low values. Models that preclude the presence of heavy tails and the related high probability of extreme concentrations could significantly undermine the accuracy of diagnostic frameworks and the effectiveness of mitigation interventions, especially for soil contamination characterized by a water volume (i.e. soil moisture) frequently approaching zero.
Unifying polar and nematic active matter: emergence and co-existence of half-integer and full-integer topological defects
Authors: Amiri Aboutaleb , Mueller Romain , Doostmohammadi Amin 
Published: January 2022

Abstract
The presence and significance of active topological defects is increasingly realised in diverse biological and biomimetic systems. We introduce a continuum model of polar active matter, based on conservation laws and symmetry arguments, that recapitulates both polar and apolar (nematic) features of topological defects in active turbulence. Using numerical simulations of the continuum model, we demonstrate the emergence of both half- and full-integer topological defects in polar active matter. Interestingly, we find that crossover from active turbulence with half-to full-integer defects can emerge with the coexistence region characterized by both defect types. These results put forward a minimal, generic framework for studying topological defect patterns in active matter which is capable of explaining the emergence of half-integer defects in polar systems such as bacteria and cell monolayers, as well as predicting the emergence of coexisting defect states in active matter.
Minimum entropy production, detailed balance and Wasserstein distance for continuous-time Markov processes
Authors: Dechant Andreas 
Published: January 2022

Abstract
We investigate the problem of minimizing the entropy production for a physical process that can be described in terms of a Markov jump dynamics. We show that, without any further constraints, a given time-evolution may be realized at arbitrarily small entropy production, yet at the expense of diverging activity. For a fixed activity, we find that the dynamics that minimizes the entropy production is driven by conservative forces. The value of the minimum entropy production is expressed in terms of the graph-distance based Wasserstein distance between the initial and final configuration. This yields a new kind of speed limit relating dissipation, the average number of transitions and the Wasserstein distance. It also allows us to formulate the optimal transport problem on a graph via continuous-time interpolating dynamics, in complete analogy to the continuous space setting. We demonstrate our findings for simple state networks, a time-dependent pump and for spin flips in the Ising model.
A differential operation principle of the automatic bus transfer system pickup unit as a way of decreasing the emergency clearing time.a
Authors: Danilov Nikolay , Tsyruk Sergey , Timonin Alexandr , Sharafeddine Karam 
Published: January 2022

Abstract
A proper choice of the design and operation algorithm of emergency control devices like high-speed bus transfer (HSBT) is only possible proceeding from a study and analysis of steady-state and transient processes in emergency modes of operation (short-circuit faults, power supply disconnection, or phase open-circuit fault). The numerical experiments for studying such modes that were carried out, using the Matlab Simulink software package, on the mathematical models of an industrial power supply system involving synchronous motors connected to it made it possible to synthesize a new differential HSBT pickup unit featuring a high-speed response to emergency events. In doing so, special attention was paid to an analysis of transient operation modes with the aim of minimizing the probability of false actuations. The obtained study results have found practical application in the HSBT devices installed at the facilities of PJSC MOSENERGO. The experience gained from the operation of a new device jointly with high-speed circuit breakers produced by the Tavrida-Elektrik state-owned corporation has demonstrated essential advantages in comparison with the conventional HSBT designs.
Diffraction grating parameter retrieval using non-paraxial structured beams in coherent Fourier scatterometry
Authors: Soman S , Pereira S F , Gawhary O El 
Published: January 2022

Abstract
In recent years, a lot of works have been published that use parameter retrieval using orbital angular momentum (OAM) beams. Most make use of the OAM of different Laguerre-Gauss modes. However, those specific optical beams are paraxial beams and this limits the regime in which they can be used. In this paper, we report on the first results on retrieving the geometric parameters of a diffraction grating by analysing the corresponding complex-valued (i.e. amplitude and phase) Helmholtz Natural Modes (HNM) spectra containing both the azimuthal (i.e. n) and radial (i.e. m) indices. HNMs are a set of orthogonal, non-paraxial beams with finite energy carrying OAM. We use the coherent Fourier scatterometry (CFS) setup to calculate the field scattered from the diffraction grating. The amplitude and phase contributions of each HNM are then obtained by numerically calculating the overlap integral of the scattered field with the different modes. We show results on the sensitivity of the HNMs to several grating parameters.
The behavior of hydrothermally synthesized hematite nanorods prepared on spin coated seed layers
Authors: Talibawo Joan , Nyarige Justine S , Kyesmen Pannan I , Cyulinyana Marie C , Diale Mmantsae 
Published: January 2022

Abstract
Herein we report on the effect of varied spin-coated seed layer concentrations of Iron (III) chloride hexahydrate (FeCl3.6H2O) on the photoelectrochemical performance of hydrothermally synthesized hematite nanorods. The seed layers were prepared from 0.05, 0.07, 0.09, 0.11, and 0.13 M concentrations of FeCl3.6H2O. The nanorods were vertically aligned with slight inclinations over the seed layers with the two lowest molar concentrations (0.05 and 0.07 M) of FeCl3.6H2O. A further increase in seed layer concentrations transformed the nanorods as they grew over others and agglomerated into clusters. Structural analysis using x-ray diffraction (XRD) and Raman spectroscopy demonstrated uniform hematite crystalline peaks for all the samples. All samples absorbed highly in the visible region within an onset absorption edge wavelength ranging from 624 to 675 nm. Overall, the nanorods synthesized over the lowest seed layer concentration of 0.05 M of FeCl3.6H2O exhibited the highest photocurrent density of 0.077 mA cm−2 at 1.5 V versus reversible hydrogen electrode. The results obtained provide important information about the structural, optical, and photoelectrochemical properties of hematite nanorods synthesized over varied seed layer concentrations. This is a key contribution in understanding and enhancing the hematite nanorods performance for photocatalytic applications.
Photocatalytic degradation of VOCs from air stream using Mo:TiO2/GAC nanocomposites
Authors: Abedi Kamaladdin , Shahmoradi Behzad , Mohammadi Ebrahim , Wantala Kitirote , Maleki Afshin , Zandsalimi Yahya , Salimi Sonya , Kohzadi Shadi 
Published: January 2022

Abstract
Modification of TiO2 is one of the techniques used to enhance its photodegradation efficiency and to make it visible-light-active. In this study, Mo-doped TiO2 nanoparticles were synthesized using a fast sol-gel technique and then coated on granular activated carbon (GAC) as both substrate and adsorbent to obtain Mo:TiO2/GAC composite. The fabricated composite was characterized by many techniques such as powder XRD, SEM, EDX, FTIR, and N2 adsorption-desorption analysis. Then, the composite was applied to photodegrade volatile organic compounds (VOCs) under both UV and visible light irradiations. The characterization results showed high crystallinity and purity. Mo:TiO2/GAC composite gave a higher photodegradation efficiency compared with bare TiO2 and bare GAC. Moreover, studying operational parameters showed that the optimum condition for photodegradation efficiency of VOCs was at a flowrate of 1 L min−1, VOCs concentration of 20 ppm, and light intensity of 400 and 600 W m−2 for UV and visible light, respectively. The results suggest that Mo:TiO2/GAC is a visible-light-active composite and can be acceptably used to decompose VOCs under visible light with adequate efficiency and without the generation of harmful by-products such as O3 as compared with UV.