bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calibrating beam fluxes of a low-energy neutral atom beam facility
Authors: Gasser Jonathan , Galli André , Wurz Peter 
Published: May 2023

Scientific detection and imaging instruments for low-energetic neutral atoms (ENA) onboard spacecraft require thorough pre-flight laboratory calibration against a well-characterized neutral atom beam source. To achieve this requirement, a dedicated test facility is available at the University of Bern, which is equipped with a powerful plasma ion source and an ion beam neutralization stage. Using surface neutralization, low-energy neutral atom beams of any desired gas species can be produced in the energy range from 3 keV down as low as 10 eV. As the efficiency of the neutralization stage is species and energy dependent, the neutralizer itself needs to be calibrated against an independent reference. We report on the calibration and characterization of this neutral atom beam source using our recently developed Absolute Beam Monitor (ABM) as a primary calibration standard. The ABM measures the absolute ENA flux independent of neutral species in the energy range from 10 eV to 3 keV. We obtain calibration factors of a few 100 cm−2 s−1 pA−1, depending on species at beam energies above about 100 eV, and a power-law decrease for energies below 100 eV. Furthermore, the energy loss of neutralized ions in the surface neutralizer is estimated from time-of-flight measurements using the ABM. The relative energy loss increases with ENA energy from low levels near zero up to 20%–35% at 3 keV, depending on atomic species. Having calibrated our neutral beam source allows for accurate calibration of ENA space instruments.
Development of a scintillator-based optical soft x-ray (OSXR) diagnostic system for KSTAR tokamak
Authors: Lee M. W. , Kim Junghee , Kim M. H. , Lim Soobin , Kim Jayhyun , Sung C. 
Published: May 2023

We have developed a new scintillator-based optical soft x-ray (OSXR) diagnostic system for KSTAR. By utilizing fiber optic faceplates, mm-size lens arrays, and fiber bundles, we have successfully constructed a novel optical system for scintillator-based soft x-ray detection to overcome the limited vacuum-port conditions in KSTAR. P47 (Y2SiO5), which has a fast rise (∼7 ns) and decay (∼100 ns) time sufficient for detecting plasma instabilities observed in the kHz–MHz spectral range, was selected as the scintillator material for the KSTAR OSXR system. Scintillation toward each detection channel is collected by the lens arrays coupled to optical fiber cores, which are connected to the photodetector system. Initial results obtained during the 2022 KSTAR experimental campaign support the validity of the OSXR data through the consistency of OSXR measurement results with other diagnostics. We also observe that the OSXR system can capture magnetohydrodynamic activities, such as sawtooth oscillations, and provide valuable information for disruption mitigation studies using shattered pellet injection.
Hierarchical off-diagonal low-rank approximation of Hessians in inverse problems, with application to ice sheet model initialization
Authors: Hartland Tucker , Stadler Georg , Perego Mauro , Liegeois Kim , Petra Noémi 
Published: May 2023

Abstract
Obtaining lightweight and accurate approximations of discretized objective functional Hessians in inverse problems governed by partial differential equations (PDEs) is essential to make both deterministic and Bayesian statistical large-scale inverse problems computationally tractable. The cubic computational complexity of dense linear algebraic tasks, such as Cholesky factorization, that provide a means to sample Gaussian distributions and determine solutions of Newton linear systems is a computational bottleneck at large-scale. These tasks can be reduced to log-linear complexity by utilizing hierarchical off-diagonal low-rank (HODLR) matrix approximations. In this work, we show that a class of Hessians that arise from inverse problems governed by PDEs are well approximated by the HODLR matrix format. In particular, we study inverse problems governed by PDEs that model the instantaneous viscous flow of ice sheets. In these problems, we seek a spatially distributed basal sliding parameter field such that the flow predicted by the ice sheet model is consistent with ice sheet surface velocity observations. We demonstrate the use of HODLR Hessian approximation to efficiently sample the Laplace approximation of the posterior distribution with covariance further approximated by HODLR matrix compression. Computational studies are performed which illustrate ice sheet problem regimes for which the Gauss–Newton data-misfit Hessian is more efficiently approximated by the HODLR matrix format than the low-rank (LR) format. We then demonstrate that HODLR approximations can be favorable, when compared to global LR approximations, for large-scale problems by studying the data-misfit Hessian associated with inverse problems governed by the first-order Stokes flow model on the Humboldt glacier and Greenland ice sheet.
Rotational (de-)excitation of protonated tricarbon monosulfide HC3S+ by collision with helium atoms
Authors: Naouai Manel , Jrad Abdelhak 
Published: May 2023

Abstract
A new two-dimensional potential energy surface of the interaction between HC3S+ molecule and helium atom is mapped using an explicitly correlated coupled cluster approach with a single, double and perturbative triple excitation-F12a approach with an augmented-correlation-consistent polarized valence triple-zeta Gaussian basis set. The deepest potential well is identified at θ = 95∘ and R = 6.0 bohr with a depth of 100.67 cm−1. Cross-sections are determined for total energy up to 300 cm−1 using a coupled states method. Thermal rate coefficients are derived from the determined cross-sections for temperatures ranging between 3 K and 50 K. A clear predominance of

|

Δ
j

|

= 2 processes is observed.
Synergism in SF6 mixtures with C=C−C backbone compounds
Authors: Egüz E A , Pachin J , Vemulapalli H , Franck C M 
Published: May 2023

Abstract
A positive synergy in the electric strength was observed in a previous study in SF6/HFO1234ze(E) mixtures which was shown to result from a strong electron energy moderation capability of HFO1234ze(E) combined with thermal electron attachment of SF6 (Egüz et al 2022 J. Phys. D: Appl. Phys.
55 315203). In the present work, the electron energy moderation properties of compounds with a similar C=C−C backbone are investigated. Swarm and breakdown measurements are performed in pure gases and in mixtures with SF6. Compounds with a trifluoromethyl group (−CF3) showed lower characteristic energy and as a consequence a positive synergism with SF6. Descriptors related to electron energy moderation are identified and computed; a clear trend is found from the analysis of descriptors related to inelastic processes which suggest(s) that vibrational excitations may be the main source of electron energy loss in the compounds showing positive synergy.
Study on the exciton dynamic processes of exciplex host–guest system by transient magnetic field effects
Authors: Chen Yiwen , Chen Liangjian , Xiao Shu , Qiao Xianfeng , Ma Dongge 
Published: May 2023

Abstract
Utilizing exciplex as the host and fluorescence emitter with dopant materials has been proved successfully to fabricate highly-efficient organic light-emitting diodes. Exciton evolution and energy transfer in this exciplex host–guest system are complex. Gaining insight into the electroluminescence (EL) mechanisms in exciplex-based devices is key for further optimizing device configuration. Here, we have investigated exciton dynamics in devices with exciplex as host and 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) as red fluorescence emitter. Two exciplexes, 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPY) doped 2,4,6-tris[3-(triphenylphosphine)phenyl]-1,3,5-triazine (POT2T), and 4,4′,4″-tris[3-methylphenyl(phenyl)amino]-triphenylamine (m-MTDATA) doped tris(8-hydroxyquinoline)aluminum(III) (Alq3), with different band energy are utilized as host materials. Combining the measurements of transient EL, transient photoluminescence and magnetic field effect (MFE), it is concluded that Dexter energy transfer, together with Förster resonance energy transfer, are confirmed in the pure fluorescence doped system. Meanwhile, it is found that DCJTB works with the hot excitons mechanism but not a traditional red fluorescence emitter as recognized previously. This work presents that the transient MFE is powerful for detecting excitonic dynamic processes in excipelx based host–guest EL systems.
Flavored leptogenesis and Dirac CP violation
Authors: Mukherjee Ananya , Narendra Nimmala 
Published: May 2023

Abstract
In this work, we pay special attention to establish the crucial role of the Casas-Ibarra parameterization in the presence of two different orthogonal matrices, R = O eiA
and R = O e
A
in order to investigate the role of Dirac CP violation in flavored leptogenesis. By considering these two choices of the R matrix we examine the connection between the low-energy and high-energy CP violations together with certain interesting predictions on the low-energy parameters, namely, the lightest neutrino mass and the Dirac CP phase (δ). By considering the right-handed neutrino (RHN) mass window to be 108 GeV, we show that Dirac-phase leptogenesis is possible with the choices of these two orthogonal matrices. The above forms of R matrices allow us to choose a nearly degenerate spectrum for the RHN masses. The complex R matrix predicts a maximal Dirac CP violation (δ = π/2) for leptogenesis, which can be verified by the ongoing and upcoming searches for a precise δ measurement at the neutrino factories. We also discuss the phenomenological implications of these two case studies within the context of lepton flavor violation (LFV) by considering the μ → e
γ decay process, in terms of an indirect probe of the R matrix parameter space. We report an upper bound on the lightest neutrino mass (m
1) of around 0.015 eV from the baryon asymmetry criteria for normal hierarchy of neutrino masses.
Signatures for shape coexistence and shape/phase transitions in even–even nuclei
Authors: Bonatsos Dennis , Martinou Andriana , Peroulis S K , Mertzimekis T J , Minkov N 
Published: May 2023

Abstract
Systematics of B(E2) transition rates connecting the first excited

0

2

+

state to the first excited

2

1

+

state of the ground state band in even–even nuclei indicates that shape coexistence of the ground state band and the first excited K = 0 band should be expected in nuclei lying within the stripes of nucleon numbers 7–8, 17–20, 34–40, 59–70, 96–112 predicted by the dual shell mechanism of the proxy-SU(3) model, avoiding their junctions, within which high deformation is expected. Systematics of the excitation energies of the

0

2

+

states in even–even nuclei show that shape coexistence due to proton-induced neutron particle-hole excitations is related to a first-order shape/phase transition from spherical to deformed shapes, while shape coexistence due to neutron-induced proton particle-hole excitations is observed along major proton shell closures.
Compound fault diagnosis method for rolling bearings based on the multipoint kurtosis spectrum and AO-MOMDEA
Authors: Wang Huibin , Yan Changfeng , Wang Zonggang , Liu Bo , Li Shengqiang , Wu Lixiao 
Published: May 2023

Abstract
In compound rolling bearing faults, different types of fault signals are coupled and cross-affected, which makes it difficult to separate and extract weak fault features, and making it easy to miss diagnoses or misdiagnose. Aiming at solving this problem, a compound fault diagnosis method for rolling bearings based on the multipoint kurtosis spectrum (MKS) and the aquila optimizer multipoint optimal minimum entropy deconvolution adjusted (AO-MOMEDA) method is proposed. Variational modal decomposition is used to reduce the noise of the original vibration signal and improve the recognition of the MKS so as to predict the fault type and preset the search range of the initial period value. A new fault feature strength index with relative amplitude difference is proposed and, combined with the kurtosis of the envelope spectrum, a multi-objective optimization function is constructed. Through the excellent optimization characteristics of the aquila optimizer, the optimal initial period value and filter length are automatically obtained. The optimized MOMEDA method is used for optimal deconvolution of different types of fault signals. Envelope demodulation of the deconvolution signal is carried out to obtain the 1.5-dimensional spectrum of the envelope signal. The types of rolling bearing composite faults are identified according to the fault features in the 1.5-dimensional spectrum. The feasibility of the proposed method is verified through measurements of the signals of rolling bearings with three different types of compound faults. The experimental results show that the proposed method can overcome the influence of strong fault signals and improve the accuracy of compound fault identification. Our results have application value in engineering practice.
Design of a line-of-sight fluorescence-based imaging diagnostic for classification of microbe species
Authors: Herzog Joshua M , Sick Volker 
Published: May 2023

Abstract
Fluorescence imaging of certain biochemicals, including flavins and pyridine nucleotides, has utility in characterizing the metabolic state of tissue and in discriminating between microbial species. There is significant clinical utility in this class of imaging techniques but most measurements reported to date require specialized training and equipment rendering most implementations unsuitable for routine medical imaging. Here, a low-cost and robust imaging technique is designed using ultraviolet-induced fluorescence of pyridine nucleotides (primarily NADH) and flavins (primarily FAD) in microbial samples. The diagnostic is optimized to distinguish between different microbial species based on previously reported spectral data using a ratiometric imaging approach. A detailed performance analysis is provided that relates the measured fluorescence intensity ratio (FIR) to the relative concentration ratio of NADH to FAD using a simplified spectroscopic model. Analysis suggests the technique is sensitive to changes in the NADH/FAD concentration ratio over several orders of magnitude, with better than 10% FIR precision on a per-pixel basis for microbial smears as thin as 10 s of microns at a resolution of 30 mm−1 and exposures of 20 ms. Representative microbe samples from eight species were imaged to demonstrate the proposed technique. Results show that the FIR varies by an order of magnitude across different species but the intra-species variation is only ∼5% for the conditions used here. An additional imaging band may be necessary to classify species that contain red pigments or bacteriochlorophyll. Radiative trapping was discussed as a possible limitation of the technique, but no clear evidence for radiative trapping was observed here. Overall, the results suggest that the proposed approach is feasible for rapid, low-cost, and robust characterization of microbial samples.
Fastening solutions on composite structures: model and verifications of contact with friction, progressive composite damage, and ductile metal damage
Authors: Erbil Emre , Karakuzu Ramazan 
Published: May 2023

Abstract
In this study, the fundamental steps required for the mechanical analysis of bolted laminated composite structures were revealed. Advanced methods were developed in Fortran and Python to implement nonlinearity to the composite material model using MARC/MENTAT finite element software. Friction and damage parameters for HTA/6376 CFRP material are verified using experimental data sources in the literature. The critical Cockroft–Latham ductile damage parameter of AISI 304L sheet material with its anisotropic properties, which is required for the design of plastically deformable metal components in the composite joint, is computed. Good agreement was obtained between the friction and progressive damage of CFRP composite, ductile damage of AISI 304L, and the external experimental references.
Multi-physics simulation of mechano-electrochemical bidirectional coupling interaction of galvanic corrosion between Al alloy and 316L SS
Authors: Hou Yue , Wang Wei , Guo Zihao , Tian Yuan , Chen Shougang 
Published: May 2023

Abstract
Due to the limitations of experimental testing in material size and time scale, this work presents a mechano-electrochemical bidirectional coupling finite element method (FEM) simulation model on account of mechanistic and corrosion kinetics understanding in Al alloy-316L SS galvanic couple. The galvanic corrosion behavior and anodic dissolution deformation of the couple in 3.5 wt.% NaCl solution were analyzed. The effect of external load on galvanic corrosion initiation and propagation was investigated based on Gutman’s theory. The FEM model reveals that the galvanic corrosion is connected with the mechanical damage and the stress concentration coefficient, and highlights the crucial role of corrosion defect in the mechanical behavior of Al alloy. The results show that the external force aggravates the galvanic corrosion at the defects, deteriorating the protection of corrosion products. The thickness of the Al (OH)3 deposition layer reflects the electrochemical reactivity at different positions on the anode surface. The mechanical damage occurs initially at the corrosion defect and then extends to the middle of the anode. The stress concentration coefficient at the center of the anode gradually exceeds the position of the corrosion defect, resulting in mechanical failure at this position.
On the role of Gd3+ ions in enhancement of UV emission from Yb3+–Tm3+ up-converting LiYF4 nanocrystals
Authors: Misiak Małgorzata , Pavlosiuk Orest , Szalkowski Marcin , Kotulska Agata , Ledwa Karolina , Bednarkiewicz Artur 
Published: May 2023

Abstract
Materials capable of emitting ultraviolet (UV) radiation are sought for applications ranging from theranostics or photodynamic therapy to specific photocatalysis. The nanometer size of these materials, as well as excitation with near-infrared (NIR) light, is essential for many applications. Tetragonal tetrafluoride LiY(Gd)F4 nanocrystalline host for up-converting Tm3+–Yb3+ activator-sensitizer pair is a promising candidate to achieve UV–vis up-converted radiation under NIR excitation, important for numerous photo-chemical and bio-medical applications. Here, we provide insights into the structure, morphology, size and optical properties of up-converting LiYF4:25%Yb3+0.5%Tm3+ colloidal nanocrystals, where 1, 5, 10, 20, 30 and 40% of Y3+ ions were substituted with Gd3+ ions. Low gadolinium dopant concentrations modify the size and up-conversion luminescence, while the Gd3+ doping that is exceeding the structure resistance limit of the tetragonal LiYF4 results in appearance of foreign phase and significant decrease of luminescence intensity. The intensity and kinetic behavior of Gd3+ up-converted UV emission are also analyzed for various gadolinium ions concentrations. The obtained results form a background for further optimized materials and applications based on LiYF4 nanocrystals.
Analyticity of the Lyapunov exponents of random products of quasi-periodic cocycles
Authors: Bezerra Jamerson , Sánchez Adriana , Tall El Hadji Yaya 
Published: May 2023

Abstract
We show that the top Lyapunov exponent

λ
+

(
p
)

,

p
=
(

p
1

,
…
,

p
N

)

with

p
i

>
0

for each i, associated with a random product of quasi-periodic cocycles depends real analytically on the transition probabilities p whenever

λ
+

(
p
)

is simple. Moreover if the spectrum at p is simple (all Lyapunov exponents having multiplicity one ) then all Lyapunov exponents depend real analytically on p.
ORBIT simulations of fast ion power loads on the wall of the Divertor Tokamak Test
Authors: Gobbin Marco , Spizzo Gianluca 
Published: May 2023

AbstractNeutral beam injection in tokamaks produces a population of fast ions, which interact with 3D magnetic fields in a variety of ways, often resulting in energetic particle losses in very short times to the wall. Careful design of neutral beams and active control of error fields helps to keep these losses to a minimum. Nevertheless, past experience in tokamaks in the 1980s and detailed simulations for future machines, such as International Thermonuclear Experimental Reactor, suggest that very localized fast ion losses (‘hot spots’) can be present, even if the overall losses are low. In this paper, we discuss this issue in the Divertor Tokamak Test (DTT) project, and we show that in the standard single-null full-power scenario of the DTT, fast ions produce two hot spots, corresponding approximately to the beam injection and exit toroidal angles: the former being mainly due to prompt losses/passing particles, while the latter is due to trapped ions. However, the maximum power load in these spots is of the order∼63 kW m−2, below the tolerance of plasma-facing components of the machine.
Statistical analysis of similarity of plasma parameters profiles at quasi-stationary stage of discharge in JET tokamak
Authors: Kukushkin A B , Sdvizhenskii P A , Flanagan J , Kos D , Neverov V S , Szepesi G , Taylor D M A 
Published: May 2023

Abstract
A statistical analysis is carried out of the similarity of profiles of plasma parameters: electron temperature T
e, density n
e, and pressure P
e, at the stage of quasi-stationary plasma current (the so called flat-top stage) of about 9000 discharges in the JET tokamak, among the discharges from #84458 to #99419 that covers almost the entire database of successful discharges in the JET ITER-like wall machine. For all these parameters, the existence of universal profiles is shown as functions of the normalized minor radius of the plasma column ρ. The discharge universal profiles (DUPs) are obtained by dividing the space-time-dependent profile by its value at the center of the plasma column or by the space-averaged value of this parameter in the region ρ ⩽ ρ
max = 0.5–1, and subsequent averaging over time at the flat-top stage of each discharge. The machine universal profiles (MUPs) are obtained by averaging over time of flat-top stage of all discharges. It is shown that for 86% of the discharges, the time-averaged relative root-mean-square deviation of P
e profile from the DUP is less than 20% at ρ ⩽ 0.8, and for the MUP, it is less than 17%. A similar picture is observed for the profiles of T
e and n
e/√T
e. An auxiliary heating, P
aux ⩾ 1 MW or 10 MW, was present at, respectively, 44% and 21% of the total duration of the flat-top stage of discharges. It is shown that large, ∼100% in magnitude, jumps of T
e at ρ = 0, caused by the switch-on of auxiliary heating, can be described with a ∼20% accuracy by the jumps of the space-averaged temperature if the DUP is used to describe the stationary shape of the temperature spatial profile. The results obtained illustrate the degree of plasma self-organization in tokamaks.