bluuebunny/crossref_metadata_2025 huggingface dataset:
Transmission and Risk Factors of COVID-19 among Health Care Workers
Authors: Alghader Majdi R.M. , Valvi Damaskini , de la Hoz Rafael E.
Published: April 2023

Coronavirus disease 2019 (COVID-19) poses a significant occupational risk factor to health care workers (HCWs). As in previous events, this occupational risk amplifies and compounds the adverse impact of the pandemic. We conducted a narrative review summarizing risk factors associated with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) transmission in HCWs. We searched for original observational studies (including case-control, cross-sectional, prospective and retrospective cohorts) using PubMed, Scopus, and Google Scholar. A total of 22 articles were reviewed, including eligible English articles published between April 2020 and May 2022. Job category, work environment, personal protective equipment (PPE) noncompliance, lack of PPE awareness and training, unvaccinated status, and competing community and household exposures were identified as risk factors for SARS-CoV-2 transmission among HCWs. Effective measures to protect HCWs from SARS-CoV-2 need to account for the identified occupational risk factors. Identifying and understanding COVID-19 risk factors among HCWs must be considered a public health priority for policy makers to mitigate occupational and community transmission in current and future epidemics.
Machine learning for product choice prediction
Authors: Martínez-Garmendia Josué
Published: April 2023

The goal of this paper is to provide a point of empirical evidence as to how machine-learning techniques stack-up in their ability to predict consumer choices relative to traditional statistical techniques. We compare a traditional (naïve) multinomial logit to six machine-learning alternatives: learning multinomial logit, random forests, neural networks, gradient boosting, support vector machines and an ensemble learning algorithm. The comparison is done by applying these methods to beer category stock keeping unit (SKU) level panel data. Results show that machine-learning techniques tend to perform better, but not always. Ensemble learning performs best while maintaining an overall high-performance level across all SKU classes, independently of their sample size. This result builds on existing evidence about the benefits of combining multiple prediction techniques over relying on a single best performing model, as conventional wisdom would intuitively make us believe. In general, the better performance of machine learning techniques at predicting product choice should not come as a surprise. At their core, machine learning techniques are designed to augment dimensionality of models and/or scan through orders of magnitude greater model alternatives, relative to the narrower focus of traditional approaches.
The strength of a weak centre: pandemic politics in the European Union and the United States
Authors: Alexander-Shaw Kate , Ganderson Joseph , Schelkle Waltraud
Published: April 2023

The European Union presents a puzzle to political systems scholars: how can a developing polity, with all its attendant functional weaknesses, be rendered politically stable even through moments of a policy crisis? Building on insights from the literature on fiscal federalism, this article challenges much conventional wisdom on Europe’s incompleteness. This is based on the corollary of Jonathan Rodden’s concept of Hamilton’s Paradox: whereas a strong centre cannot resist exploitation by states because it has the means to rescue them, a weak centre’s lack of exploitable capacity may induce states to support, and even empower, it in a crisis. This article argues that in providing a contemporaneous stress-test, Covid-19 serves to expose both the pathologies of a strong-centred federation and the surprising resilience of a weak one. It highlights three polity features—powers, decision-making modes and integrity—and charts their political implications during an acute crisis. The article argues that in the EU these features incentivise cooperative ‘polity maintenance’ between polarised states, a feature absent in an American polity marked by rivalry between polarised parties. The article thus challenges notions that the EU’s incompleteness necessarily leads it to dysfunction or that it should strive to emulate established federations.
Financial constraints and firms’ markup: evidence from China
Authors: Yue Wen , Li Xuefei
Published: April 2023

Using the micro data of Chinese manufacturing firms, this study analyzes the impact of financial constraints on firms’ markup and their influence mechanism. The findings suggest that financial constraints significantly reduce firms’ markup. The result is still valid after a series of robustness tests, such as key indicator substitution, analysis of endogeneity problems, controlling for other policy changes, dynamic panel model estimation, and quantile regression. An analysis of the influence mechanism shows that, on the one hand, financial constraints inhibit the improvement of firms’ production efficiency and reduce its markup through the productivity channel; on the other hand, financial constraints also reduce firms’ market pricing power and exert a significant negative impact on firms’ markup through the market pricing channel. At the same time, significant heterogeneity exists in the negative impact of financial constraints among different firm types. This paper not only enriches our understanding of the relationship between financial constraints and firms’ markup, but also provides a new perspective for a more comprehensive grasp of the micro economic effects of financial constraints.
Promoting progress in plasma surface biofunctionalization
Authors: Ikenson Ben
Published: April 2023

Emerging technologies could enable shift from wet chemical approaches for biomedical applications
Low-drift-rate external cavity diode laser
Authors: Chang Eddie H. , Rivera Jared , Bostwick Brian , Schneider Christian , Yu Peter , Hudson Eric R. ,   HUNTER Collaboration
Published: April 2023

We present the design, construction, and simulation of a simple, low-cost external cavity diode laser with a measured free-running frequency drift rate of 1.4(1) MHz/h at 852 nm. This performance is achieved in a compact aluminum structure held inside an airtight, temperature-controlled enclosure. The high thermal conductivity of the laser cavity and the stable temperature environment inside the enclosure minimize the time-varying, spatial temperature gradients across the laser cavity. We present thermal finite element method simulations, which quantify the effects of temperature gradients, and suggest that the drift rate is likely limited by the laser-diode and piezo-aging.
Hot electron scaling for two-plasmon decay in ICF plasmas
Authors: Rovere E. , Colaïtis A. , Follett R. K. , Casner A.
Published: April 2023

We present a parametric scaling of hot electron (HE) generation at quarter critical density from the two-plasmon decay process. The study is conducted with the laser plasma simulation environment code, considering Langmuir decay instabilities (LDI) and laser pump depletion in 2D. The parameter scan is conducted as a function of electron temperature, ion–electron temperature ratio, drive strength, and density scale length. The scaling shows an hot electron (HE) conversion fraction up to 40%, HE fluxes up to 6 × 10 14 W / cm 2, and average temperatures in the range of 30 to 100 keV. The electron angular distributions exhibit two main regions: the plasma “bulk,” characterized by homogeneous emission, up to energies of 30 − 60 keV depending on the individual laser–plasma conditions, and a HE tail after ≃ 50 − 60 keV. The mid-energy electrons are homogeneously emitted toward the end of the plasma bulk and acquire energy through electron plasma wave (EPW) Landau damping from Langmuir wave collapse and LDI cascade. The HE tail has electrons emitted in the forward direction and at low divergence, due to turbulence and EPW Landau damping from multi-staged acceleration. Finally, the laser power transmitted through the quarter critical region reaches values from ∼ 80 % down to ∼ 35 % for increasing HE generation, with absorption due to EPW collisional damping in the range of ∼ 10 % − 35 %.
Data processing techniques for ion and electron-energy distribution functions
Authors: Caldarelli A. , Filleul F. , Boswell R. W. , Charles C. , Rattenbury N. J. , Cater J. E.
Published: April 2023

Retarding field energy analyzers and Langmuir probes are routinely used to obtain ion and electron-energy distribution functions (IEDF and EEDF). These typically require knowledge of the first and second derivatives of the current–voltage characteristics, both of which can be obtained using analog and numerical techniques. A frequent problem with electric-probe plasma diagnostics is the noise from the plasma environment and measurement circuits. This poses challenges inherent to differentiating noisy signals, which often require prior filtering of the raw current–voltage data before evaluating the distribution functions. A review of commonly used filtering and differentiation techniques is presented. It covers analog differentiator circuits, polynomial fitting (Savitzky–Golay filter and B-spline fitting), window filtering (Gaussian and Blackman windows) methods as well as the AC superimposition and Gaussian deconvolution routines. The application of each method on experimental datasets with signal-to-noise ratios ranging from 44 to 66 dB is evaluated with regard to the dynamic range, energy resolution, and signal distortion of the obtained IEDF and EEDF as well as to the deduced plasma parameters.
On power and fundamental resistance relations in symmetric RF CCPs by simulating simplified nonlinear circuits
Authors: Du M. Q. , Ding Z. F.
Published: April 2023

Voltage and current measured from radio frequency (RF) capacitively coupled plasmas (CCPs) are basic data, from which various powers and impedances are subsequently calculated via fast Fourier transform to gain deep insight into RF CCPs. The specific values of these parameters depend on the nonlinearity of RF CCPs and the interaction with the external circuit, but the relation between harmonic powers and that among the fundamental resistances are not known. These questions are investigated via Multisim software by simplifying the symmetric RF CCP with the nonlinear circuit consisting of a linear resistor and a nonlinear capacitor. The results show that the calculated total RF power is accurately equal to that dissipated by the resistor in discharge. However, it is not true for the fundamental power and harmonic one. The fundamental resistance calculated at the external electrode, which was previously proposed as the plasma resistance, is higher than the latter. The conversion between the fundamental and harmonic powers in the nonlinear ideal capacitor of RF CCPs is the origin of the obtained abnormal feature. In comparison, the plasma resistance calculated from the total RF power and current is unaffected by harmonics and is, thus, more credible, despite that this method requires an assumption of constant transient plasma resistance.
Relativistic analysis of upper hybrid wave propagation and trapping
Authors: Hansen S. K. , Nielsen S. K. , Stober J. ,   EUROfusion MST1 Team,   ASDEX Upgrade Team
Published: April 2023

We investigate the impact of relativistic effects on upper hybrid (UH) waves in plasmas with thermal electrons, particularly focusing on modifications of the conditions under which UH wave trapping and related low-threshold parametric decay instabilities (PDIs) may occur. A moderately relativistic (MR) dispersion relation for UH waves, valid for electron temperatures up to 25 keV and wave frequencies up to twice the electron cyclotron frequency, is obtained from previous results and shown to reduce to the warm non-relativistic result commonly used for PDI studies at low electron temperatures. The conditions under which MR UH waves propagate are then determined and compared with warm and cold plasma theory, showing a general increase in the electron density and background magnetic field strength at which the UH resonance occurs for finite electron temperatures. We next investigate the impact of the MR corrections on the possibility of UH wave trapping for X-mode electron cyclotron resonance heated (ECRH) plasmas at the ASDEX Upgrade tokamak and scaled versions of the ASDEX Upgrade parameters with core electron temperatures resembling those expected in ITER X-mode ECRH plasmas. The MR UH wave trapping conditions are virtually unchanged for ASDEX Upgrade relative to warm theory, due to the low electron temperatures, while potentially important differences between warm and MR theory exist for ITER-like core electron temperatures; cold theory is found to be insufficient in both cases. Finally, the MR dispersion relation is shown to qualitatively reproduce the PDI thresholds from warm theory for previously studied ASDEX Upgrade cases.
Dynamical process in the stagnation stage of the double-cone ignition scheme
Authors: Fang K. , Zhang Y. H. , Dong Y. F. , Zhang T. H. , Zhang Z. , Yuan X. H. , Li Y. T. , Zhang J.
Published: April 2023

In the double-cone ignition scheme, two deuterium–tritium shells in a pair of head-on Au cones are compressed and accelerated spherically [Zhang et al., Philos. Trans. R. Soc. A. 378 (2184), 20200015 (2020)]. The high-speed plasma jets from the cone tips collide and form a stagnating plasma with a higher density during the stagnation stage, preheating the plasma by the Coulomb potential. The preheated plasma is then rapidly heated up further to the ignition temperature by fast electrons generated by a powerful laser pulse of 10 ps. The conditions of the stagnating plasma strongly affect the fast-heating efficiency and consequently the success of ignition. In order to understand dynamical process in the stagnation stage, a special experimental campaign was conducted, where the evolution of the stagnating plasma was diagnosed through the temporal resolved self-emission signals. The spatial-temporal distributions of temperature and density of the colliding plasma were analyzed by the Abel inversion algorithm and the Legendre polynomial fitting. The stagnation period was found to be about 300 ps, the temperature of the core area of the stagnated plasma was between 340 and 390 eV, while the aspect ratio of the colliding plasma was about 0.78.
Absolute and global instabilities driven by Cherenkov interaction between magnetized electron beam and spoof surface plasmon polaritons
Authors: Annaka Y. , Ogura K. , Ito M.
Published: April 2023

In this study, we examine absolute and global instabilities driven by the Cherenkov interaction between a magnetized electron beam and spoof surface plasmon polaritons (SPPs) with an azimuthal mode number m. The absolute and global instabilities are induced in long and short lengths of the cylindrical corrugated waveguides (CCWs), respectively. The temporal and spatial growth rates have different dominant modes of spoof SPPs that, respectively, affect the absolute and global instabilities. In the experiment, the G-band radiation, which corresponds to the dominant mode in the spatial growth rate, is observed with the short length CCW. In the long CCW, the G-band radiation vanishes because the dominant mode in the temporal growth rate has lower frequency than the G-band cutoff frequency of the detecting system. Our results demonstrate that the instability and the multimode radiation are changed by the length of the CCW.
Disruption halo current rotation scaling on Alcator C-Mod and HBT-EP
Authors: Saperstein A. R. , Tinguely R. A. , Granetz R. S. , Levesque J. P. , Mauel M. E. , Navratil G. A.
Published: April 2023

Asymmetric halo currents (HCs) can exert large net forces on the vacuum vessel and other components during disruptions on tokamaks. The displacements caused by these forces can then be amplified if these asymmetric forces rotate at frequencies resonant with the vessel. This paper reports on the investigation of a recently proposed scaling law for the disruption HC rotation frequency [Saperstein et al., “Halo current rotation scaling in post-disruption plasmas,” Nucl. Fusion 62, 026044 (2022)] that combines measurements on Alcator C-Mod with those on HBT-EP. We find that a new non-circular version of the scaling law [ ⟨ f rot ⟩ m / ⟨ m ⟩ ∝ 1 B T ( S / π )] takes into consideration the dependence of frot on the poloidal structure of the MHD instability (m) driving the asymmetry and describes the disruption-averaged rotation frequency on C-Mod. Disruption rotation is also found to be insensitive to the vertical position and impurity content of the plasma at the onset of the disruption. However, a stagnation in the time evolution of frot is occasionally observed. Observations are consistent with the dominance of poloidal rotation during the disruption, which is motivated by the poloidal drift nature of the scaling law.
A multi-fragment real-time extension of projected density matrix embedding theory: Non-equilibrium electron dynamics in extended systems
Authors: Yehorova Dariia , Kretchmer Joshua S.
Published: April 2023

In this work, we derive a multi-fragment real-time extension of the projected density matrix embedding theory (pDMET) designed to treat non-equilibrium electron dynamics in strongly correlated systems. As in the previously developed static pDMET, the real time pDMET partitions the total system into many fragments; the coupling between each fragment and the rest of the system is treated through a compact representation of the environment in terms of a quantum bath. The real-time pDMET involves simultaneously propagating the wavefunctions for each separate fragment–bath embedding system along with an auxiliary mean-field wavefunction of the total system. The equations of motion are derived by (i) projecting the time-dependent Schrödinger equation in the fragment and bath space associated with each separate fragment and by (ii) enforcing the pDMET matching conditions between the global 1-particle reduced density matrix (1-RDM) obtained from the fragment calculations and the mean-field 1-RDM at all points in time. The accuracy of the method is benchmarked through comparisons to time-dependent density-matrix renormalization group and time-dependent Hartree–Fock (TDHF) theory; the methods were applied to a one- and two-dimensional single-impurity Anderson model and multi-impurity Anderson models with ordered and disordered distributions of the impurities. The results demonstrate a large improvement over TDHF and rapid convergence to the exact dynamics with an increase in fragment size. Our results demonstrate that the real-time pDMET is a promising and flexible method that balances accuracy and efficiency to simulate the non-equilibrium electron dynamics in heterogeneous systems of large size.
Deciphering the evolution of flavin-dependent monooxygenase stereoselectivity using ancestral sequence reconstruction
Authors: Chiang Chang-Hwa , Wymore Troy , Rodríguez Benítez Attabey , Hussain Azam , Smith Janet L. , Brooks Charles L. , Narayan Alison R. H.
Published: April 2023

Controlling the selectivity of a reaction is critical for target-oriented synthesis. Accessing complementary selectivity profiles enables divergent synthetic strategies, but is challenging to achieve in biocatalytic reactions given enzymes’ innate preferences of a single selectivity. Thus, it is critical to understand the structural features that control selectivity in biocatalytic reactions to achieve tunable selectivity. Here, we investigate the structural features that control the stereoselectivity in an oxidative dearomatization reaction that is key to making azaphilone natural products. Crystal structures of enantiocomplementary biocatalysts guided the development of multiple hypotheses centered on the structural features that control the stereochemical outcome of the reaction; however, in many cases, direct substitutions of active site residues in natural proteins led to inactive enzymes. Ancestral sequence reconstruction (ASR) and resurrection were employed as an alternative strategy to probe the impact of each residue on the stereochemical outcome of the dearomatization reaction. These studies suggest that two mechanisms are active in controlling the stereochemical outcome of the oxidative dearomatization reaction: one involving multiple active site residues in AzaH and the other dominated by a single Phe to Tyr switch in TropB and AfoD. Moreover, this study suggests that the flavin-dependent monooxygenases (FDMOs) adopt simple and flexible strategies to control stereoselectivity, which has led to stereocomplementary azaphilone natural products produced by fungi. This paradigm of combining ASR and resurrection with mutational and computational studies showcases sets of tools for understanding enzyme mechanisms and provides a solid foundation for future protein engineering efforts.
Yeast PIC-mediator structure with RNA polymerase II C-terminal domain
Authors: Schilbach Sandra , Wang Haibo , Dienemann Christian , Cramer Patrick
Published: April 2023

For transcription initiation, RNA polymerase II (Pol II) forms a preinitiation complex (PIC) that associates with the general coactivator Mediator. Whereas atomic models of the human PIC-Mediator structure have been reported, structures for its yeast counterpart remain incomplete. Here, we present an atomic model for the yeast PIC with core Mediator, including the Mediator middle module that was previously poorly resolved and including subunit Med1 that was previously lacking. We observe three peptide regions containing eleven of the 26 heptapeptide repeats of the flexible C-terminal repeat domain (CTD) of Pol II. Two of these CTD regions bind between the Mediator head and middle modules and form defined CTD–Mediator interactions. CTD peptide 1 binds between the Med6 shoulder and Med31 knob domains, whereas CTD peptide 2 forms additional contacts with Med4. The third CTD region (peptide 3) binds in the Mediator cradle and associates with the Mediator hook. Comparisons with the human PIC-Mediator structure show that the central region in peptide 1 is similar and forms conserved contacts with Mediator, whereas peptides 2 and 3 exhibit distinct structures and Mediator interactions.
Ultrafast electron localization and screening in a transition metal dichalcogenide
Authors: Schumacher Z. , Sato S. A. , Neb S. , Niedermayr A. , Gallmann L. , Rubio A. , Keller U.
Published: April 2023

The coupling of light to electrical charge carriers in semiconductors is the foundation of many technological applications. Attosecond transient absorption spectroscopy measures simultaneously how excited electrons and the vacancies they leave behind dynamically react to the applied optical fields. In compound semiconductors, these dynamics can be probed via any of their atomic constituents with core-level transitions into valence and conduction band. Typically, the atomic species forming the compound contribute comparably to the relevant electronic properties of the material. One therefore expects to observe similar dynamics, irrespective of the choice of atomic species via which it is probed. Here, we show in the two-dimensional transition metal dichalcogenide semiconductor MoSe
2
, that through a selenium-based core-level transition we observe charge carriers acting independently from each other, while when probed through molybdenum, the collective, many-body motion of the carriers dominates. Such unexpectedly contrasting behavior can be explained by a strong localization of electrons around molybdenum atoms following absorption of light, which modifies the local fields acting on the carriers. We show that similar behavior in elemental titanium metal [M. Volkov
et al.
,
Nat. Phys.
15
, 1145–1149 (2019)] carries over to transition metal-containing compounds and is expected to play an essential role for a wide range of such materials. Knowledge of independent particle and collective response is essential for fully understanding these materials.
Regional comparison SIM.QM-S5 - natural gas
Authors: Delgado Jorge Koelliker , Kang Namgoo , Ramírez Nambo Carlos , Ramírez Flores Diana Gabriela , Murillo Francisco Rangel , Bae Hyun-Kil , Moon Dong-Min , Lee Sangil , Avendaño Paola , Flores Liliana , Delgado Mabel , Alí Acco Garcia Steve , Zambrano Rocío Carla Taquire , Bohórquez Andrés Felipe Peralta , Chamorro Andrea , Rosso Adriana , Arechavaleta Mariana Ruiz de , Fioravante Andreia de Lima , Augusto Cristiane Rodrigues
Published: April 2023

Main text

The knowledge of natural gas composition is relevant for custody transfer operations. The determination of its composition is often used as the basis for the calculation of the calorific value. This report is a supplementary comparison organized for the Latin American region at SIM for components from methane to n-hexane, nitrogen, and carbon dioxide with a total of ten components. The traveling standards were obtained from an external source and checked for homogeneity and stability by CENAM before and after the measurements by participants and confirming the values under the involvement of two coordinating laboratories (CENAM and KRISS).

The level of uncertainties of this comparison were not the traditional lower uncertainties for natural gas by long-established NMIs. Nevertheless, the results from the comparison are a useful official starting point for the SIM region. All results usually agree at levels higher than 0.6 % with the comparison reference value.

The combination of the complexity of the samples being obtained from an external provider, the loss of performance of methods and instruments used by CENAM, and the use of traveling standards all contributed to the unexpectedly higher uncertainties of measurement results of this study. It should also be noted that some participating laboratories did not consider normalizing their results and did not apply all appropriate corrections. For the reference value, all normalized amount fractions have been used and uncertainties propagated appropriately.

To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.

The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Noninvasive measurement of temperature for simulated tissue based on piezoelectric micromachined ultrasonic transducers
Authors: Chen Yizhou , Qu Mengjiao , Huang Yuping , Zheng Zaiping , Cui Peijuan , Liu Huicong , Xie Jin
Published: April 2023

This paper reports a noninvasive measurement of temperature for simulated tissue based on an AlN piezoelectric micromachined ultrasonic transducer array. Polydimethylsiloxane and a built-in heating plate are used to simulate the thermal therapy of human tissue. Based on time-of-flight (ToF) from the simulated tissue surface to the heating plate surface and corresponding temperature data, the piecewise linear fitting method is used to fit the ToF-temperature curve, and its sensitivity is

41.5
 

ns

∘

C

−
1

(below 50 °C) and

30.5
 

ns

∘

C

−
1

(from 50 °C to 65 °C). The average error of real-time temperature measurements is 0.58 °C for temperatures below 65 °C. The proposed method can provide a good solution for temperature detection during thermal therapy.
Machine learning-based prediction of operation conditions from plasma plume images of atmospheric-pressure plasma reactors
Authors: Bong Cheolwoo , Kim Byeong Soo , Ali Mohammed H A , Kim Dongju , Bak Moon Soo
Published: April 2023

A technique was proposed in this paper to monitor the key operating conditions of a plasma abatement system, which are the concentration of the carbon-containing process gas and the treatment flowrate, from a plasma plume image acquired using an inexpensive color camera. The technique is based on the observation that the shape and color of the plasma plume vary with the variations in the specific energy input and plasma gas composition. In addition, because these variations are marginal and it is challenging to identify an analytical relationship between these variations and the operating conditions, the prediction model is obtained in a data-driven manner. Specifically, the model was composed of a set of convolutional autoencoders (CAEs) and a dense neural network. Furthermore, it was trained only with images captured under normal operation so that (1) images captured under abnormal operations could be identified based on the reconstruction error of the trained CAEs and (2) predictions are made only on normal images. As a demonstration, methane was tested as a process gas, and oxygen was used as a reaction agent in a nitrogen-rich environment. The test results showed that the optimized model could predict the treatment flowrate and process gas concentration with 96% probability within ±3.08 slpm and ±300 ppm, respectively.
An imbalanced sample intelligent fault diagnosis method using data enhancement and improved broad learning system
Authors: Lu Jiantao , Cui Rongqing , Li Shunming
Published: April 2023

Broad learning system (BLS) has been widely applied in the field of fault diagnosis because of its high computational efficiency, simple structure, and strong interpretability. However, traditional BLS cannot extract deep level fault features. Meanwhile, some fault samples are difficult to obtain, which leads to the imbalance of samples and further affects the diagnostic results of BLS. To solve these problems, an improved BLS fault diagnosis method based on data enhancement and multi-domain feature fusion is proposed. First, to solve the problem of sample imbalance, some false samples are generated through deep convolutional generative adversarial networks. Second, to solve the problem of poor feature extraction ability of BLS, the multi-domain feature extraction and feature optimization based on ReliefF algorithm are carried out for the enhanced samples. Compared with traditional BLS, the improved BLS effectively solves the problem of sample imbalance and greatly improves the diagnostic accuracy. The proposed method is then testified on the rolling bearing fault simulation test bench. The results show that, samples generated by the proposed method are highly similar to the real samples. In addition, the diagnostic accuracy of the BLS after multi-domain feature extraction and optimization is improved by about 19.67%, which proves the effectiveness of the method. This method provides a new perspective in fault diagnosis and could further expand the application of BLS in fault diagnosis.
Recursive spatial-temporal clustering-based target detection with millimeter-wave radar point cloud
Authors: Bi Zhicheng , Gao Yu , Wang Chaofeng , Liu Zhenghai , Wan Yaping , Yang Xiaohua
Published: April 2023

Millimeter-wave (mmWave) radar plays a vital role in a wide range of applications such as security surveillance and environmental monitoring. This work investigates target detection with radar point cloud measurements in the slow-motion scenario. In contrast to the existing spatial domain clustering-based target detection methods, we adopt a recursive spatial-temporal clustering (STC)-based method to detect targets in the spatial and temporal domain jointly. Specifically, the points belonging to targets are obtained by clustering with a distance metric defined in the spatial-temporal domains. In addition, to ensure the feasibility of the proposed method for practical real-time implementation, a speed-up scheme that intends to reduce the computational complexity induced by clustering in both spatial and temporal dimensions is developed. We demonstrate the efficacy of the proposed recursive STC-based method through experimental mmWave radar point cloud data where multiple people walk simultaneously in an open space. The proposed method achieves decent target detection performance improvement compared to a widely-used clustering method for target detection while its computation time is negligible compared to radar data reception time.
Preparation of carnation-like Ag-ZnO composites for enhanced photocatalysis under visible light
Authors: Vu Anh-Tuan , Mac Van Hung , Nguyen Thanh Hung , Nguyen Thu Huong
Published: April 2023

Carnation-like ZnO was synthesized by the facile precipitation method (at room temperature and in 120 min) to decompose dyes in an aqueous medium. The carnation-like ZnO had a stratified porous structure with a size of about 2–3 μm, its petals had a smooth surface with a thickness of 5–10 nm and a width of about 300–500 nm. Ag-ZnO composites were synthesized using glucose with the assistance of PVP. The morphology of Ag-ZnO composites was almost unchanged compared to ZnO. Where, the Ag nanoparticles in the size range of 5–15 nm were uniformly dispersed on the ZnO petals, improving the catalytic ability of the composites in tartrazine (TA) degradation. The influence of Ag content on catalytic structure and performance of composite was studied. The 5Ag-ZnO sample had the highest BET surface area and pore volume and the lowest gap energy (Eg) among the as-synthesized samples. The 5Ag-ZnO sample proclaimed the degradation efficiency in 70 min of 97.8% and the k
ap of 0.031 min−1. The influences of catalyst content, solution pH, and concentration of dye on the photodegradation efficiency of the composite were thoroughly studied. Besides, the photocatalytic activity of the composite was demonstrated by degrading various organic substances and reusability. In addition, it was compared to a metal-semiconductor catalyst of Au-ZnO and semiconductor-semiconductor catalysts of MoS2-ZnO, Cu2O-ZnO, and SiO2-ZnO. The catalytic mechanism under visible light was proposed.
Porphyrin conjugated polymer/Pt-loaded graphite carbon nitride nanocomposites for efficient charge separation and broadband responsive H2 evolution
Authors: Zeng Peng , Xu Lei , Jia Huaiyang , Liang Cuien , Li Renjie , Peng Tianyou
Published: April 2023

An efficient broadband responsive two-dimensional (2D) heterometallic Zn-/Co-porphyrin conjugated polymer (ZnCoP-F CP) with its Co-porphyrin bridging unit bearing two perfluorophenyls is coupled with 2.0 wt% Pt-loaded graphite carbon nitride (PCN) to fabricate a novel 2D/2D nanocomposite (ZnCoP-F/PCN). The resultant ZnCoP-F/PCN composite with an optimal mass ratio exhibits broadband (UV–vis–NIR) responsive H2 evolution reaction (HER) activity up to 432 μmol h−1, 5.2 and 2.8 times higher than that of the ZnCoP-F CP (83 μmol h−1) and PCN (151 μmol h−1) alone, respectively. Furthermore, the ZnCoP-F/PCN displays excellent apparent quantum yields (AQY) of 18.2%, 18.3%, 17.6%, 16.5%, 13.9%, 8.7%, 5.1%, 4.3%, 1.9%, 0.95% and 0.62% at 350, 380, 420, 450, 500, 550, 600, 700, 785, 850 and 950 nm, which are also higher than that of ZnCoP-F CP illuminated at the respective monochromatic light. The enhanced broadband responsive HER performance of ZnCoP-F/PCN can be attributed to the easily assembled ZnCoP-F CP and PCN nanosheets through strong π–π stacking interaction, which can facilitate the fast charge transfer from ZnCoP-F CP to PCN for HER. This work opens a new pathway to fabricate porphyrin polymer-based nanocomposite for more efficiently converting solar radiation and water into H2.
The strong vanishing viscosity limit with Dirichlet boundary conditions
Authors: Kelliher James P
Published: April 2023

We adapt methodology of Tosio Kato to establish necessary and sufficient conditions for the solutions to the Navier–Stokes equations with Dirichlet boundary conditions to converge in a strong sense to a solution to the Euler equations in the presence of a boundary as the viscosity is taken to zero. We extend existing conditions for no-slip boundary conditions to allow for nonhomogeneous Dirichlet boundary conditions and curved boundaries, establishing several new conditions as well. We give a brief comparison of various correctors appearing in the literature used for similar purposes.
Global martingale and pathwise solutions and infinite regularity of invariant measures for a stochastic modified Swift–Hohenberg equation
Authors: Wang Jintao , Zhang Xiaoqian , Li Chunqiu
Published: April 2023

We consider a 2D stochastic modified Swift–Hohenberg equations with multiplicative noise and periodic boundary. First, we establish the existence of local and global martingale and pathwise solutions in the regular Sobolev space

H

2
m

for each

m
⩾
1

. Associated with the unique global pathwise solution, we obtain a Markovian transition semigroup. Then, we show the existence of invariant measures and ergodic invariant measures for this Markovian semigroup on

H

2
m

. At last, we improve the regularity of the obtained invariant measures to

H

2
(
m
+
1
)

. With appropriate conditions on the diffusion coefficient, we can deduce the infinite regularity of the invariant measures, which was conjectured by Glatt-Holtz et al in their situation (2014 J. Math. Phys.
55 277–304).
A pedagogical experimental setup to measure quantum transport
Authors: Caiza Byron , Medina Ernesto , Sabater Carlos , Brämer-Escamilla Werner
Published: April 2023

We designed and built a compact device capable of measuring electronic transport in atomic-sized contacts. This experimental setup is based on the break-junction (BJ) approach. According to the samples used as electrodes, we named the instrument a Surface-Tip Break Junction. Our instrument, like a scanning tunnelling microscope in the BJ configuration, can measure the quantum transport in atoms captured by electrodes. In our case, to measure this transport, we included a homemade I–V converter, a low-cost oscilloscope, and a mobile phone that functions as a data acquisition system. Moreover, we developed a protocol to analyse the digitized data obtained from the oscilloscope. This low-cost pedagogical setup offers the possibility of implementation in undergraduate and graduate laboratories.
Investigating spatial variations in dynamic cerebral autoregulation through a computational model of stenosis
Authors: Tong Zheng , Payne Stephen J
Published: April 2023

Objective. Dynamic cerebral autoregulation (dCA) is a well-established mechanism that acts to maintain cerebral blood flow (CBF) reasonably constant in response to short-term fluctuations in blood pressure. It is known to be impaired in many clinical conditions, including stenosis, which is also a major risk factor for ischaemic stroke. However, it is not yet well understood whether impairment in dCA in one brain region is independent or not on dCA impairment in other brain regions, for example, whether there are spatial effects of stenosis on dCA. This is due to the complex blood flow environment and the lack of physiological experiments. Approach. We thus establish and apply a novel computational stenosis model including the circle of Willis to investigate and to quantify the degree of dCA impairment and CBF patterns as a function of stenosis fraction, measured in different configurations of the cerebral vasculature. Main results. We find some evidence for dependence between dCA in different brain regions, although this is very preliminary and much more experimental data will be required to answer this question fully. Significance. Our study has provided a first attempt to consider the effect of stenosis in various arteries on cerebral autoregulation to investigate spatial variations in dCA. This has potential applications in the treatment of cerebrovascular diseases where the control of cerebral perfusion is critical but where measurements are scarce.
Melting, reentrant ordering and peak effect for Wigner crystals with quenched and thermal disorder
Authors: Reichhardt C , Reichhardt C J O
Published: April 2023

We consider simulations of Wigner crystals in solid state systems interacting with random quenched disorder in the presence of thermal fluctuations. When quenched disorder is absent, there is a well defined melting temperature determined by the proliferation of topological defects, while for zero temperature, there is a critical quenched disorder strength above which topological defects proliferate. When both thermal and quenched disorder are present, these effects compete, and the thermal fluctuations can reduce the effectiveness of the quenched disorder, leading to a reentrant ordered phase in agreement with the predictions of Nelson (1983 Phys. Rev. B 27 2902–14). There are two competing theories for the low temperature behavior, and our simulations show that both capture aspects of the actual response. The critical disorder strength separating ordered from disordered states remains finite as the temperature goes to zero, as predicted by Cha and Fertig (1995 Phys. Rev. Lett.
74 4867–70), instead of dropping to zero as predicted by Nelson. At the same time, the critical disorder strength decreases with decreasing temperature, as predicted by Nelson, instead of remaining constant, as predicted by Cha and Fertig. The onset of the reentrant phase can be deduced based on changes in the transport response, where the reentrant ordering appears as an increase in the mobility or the occurrence of a depinning transition. We also find that when the system is in the ordered state and thermally melts, there is an increase in the effective damping or pinning. This produces a drop in the electron mobility that is similar to the peak effect phenomenon found in superconducting vortices, where thermal effects soften the lattice or break down its elasticity, allowing the particles to better adjust their positions to take full advantage of the quenched disorder.
Grey-level intensity measurements processing by means of Volterra equations and Least Squares Method for Video restoration
Authors: Cuesta E , Finat J , Sánchez J
Published: April 2023

In this paper a video sequence is considered as a two dimensional time evolving process. Under this assumption two Volterra equations based mathematical models are introduced for video restoration purposes. The first one is based on geometric features related to the spatial–time structure of the video sequence and gives rise to a nonlinear Volterra equation. This model arises from the Mean Curvature Flow linked to evolving surfaces. The second one is based on analytic features and leads to the formulation of a linear Volterra model. The second procedure relies on the assumption of local time coherence in the sequence of frames, at least short back in time. In both cases Volterra equations based approach introduces a memory effect in the process which in the present terminology means that several frames back may be taken into account for the better reconstruction of the current frame throughout a convenient choice of the convolution kernel. On the other hand the role played by Least Squares Method focuses on the practical computation of that convolution kernel just at discrete level. The performance of both approaches is shown through a list of suitable experiments, and the better performance of the second approach is illustrated with remarkable improvements in critical cases.
Periodical polarization reversal modulation in multiferroic MnWO4 under high magnetic fields
Authors: Liu 刘 Congbin 从斌 , Cheng 程 Jinbing 晋炳 , He 何 Junbao 俊宝 , Zhu 朱 Yongsheng 永胜 , Chang 常 Wan 婉 , Lu 路 Xiaoyu 晓宇 , Wang 王 Junfeng 俊峰 , Cui 崔 Meiyan 美艳 , Huang 黄 Jinshu 金书 , Zhou 周 Dawei 大伟 , Chen 陈 Rui 瑞 , Jiang 江 Hao 浩 , Ma 马 Chuangchuang 创创 , Dong 董 Chao 超 , Luo 罗 Yongsong 永松
Published: April 2023

We report polarization reversal periodically controlled by the electric field in multiferroic MnWO4 with a pulsed field up to 52 T. The electric polarization cannot be reversed by successive opposite electric fields in low magnetic fields (< 14 T) at 4.2 K, whereas polarization reversal is directly achieved by two opposite electric fields under high magnetic fields (< 45 T). Interestingly, the polarization curve of rising and falling fields for H ∥ u (magnetic easy axis) is irreversible when the magnetic field is close to 52 T. In this case, the rising and falling polarization curves can be individually reversed by the electric field, and thus require five cycles to recover to the initial condition by the order of the applied electric fields (+E, −E, −E, +E, +E). In addition, we find that ferroelectric phase IV can be tuned from parallel to antiparallel in relation to ferroelectric phase AF2 by applying a magnetic field approximated to the c axis.
Measurement of the relative neutron sensitivity curve of a LaBr3(Ce) scintillator based on the CSNS Back-n white neutron source
Authors: Liu 刘 Jian 建 , Wang 王 Dongming 东明 , Fu 甫 Yuecheng 跃成 , Li 李 Zhongbao 忠宝 , Yi 易 Han 晗 , Yi 易 Longtao 龙涛
Published: April 2023

A scintillator detector consisting of a LaBr3(Ce) (0.5%) scintillator, a photomultiplier tube (PMT), and an oscilloscope were used to study the neutron sensitivities of the LaBr3(Ce) scintillator at the China Spallation Neutron Source (CSNS) Back-n white neutron source in the double-bunch and single-bunch operation modes, respectively. Under the two operational modes, the relative neutron sensitivity curves of the LaBr3(Ce) scintillator in the energy regions of 1–20 MeV and 0.5–20 MeV were obtained for the first time. In the energy range of 1–20 MeV, the two curves were nearly identical. However the relative neutron sensitivity uncertainties of the double-bunch experiment were higher than those of the single-bunch experiment. The above results indicated that the single-bunch experiment’s neutron sensitivity curve has a lower minimum measurable energy than the double-bunch experiment. Above the minimum measurable energy of the double-bunch experiment, there is little difference between the measured relative neutron sensitivity curves of the single-bunch and double-bunch experiments of the LaBr3(Ce) scintillator and those of other scintillators with a similar neutron response signal intensity.
Climate-driven land surface phenology advance is overestimated due to ignoring land cover changes
Authors: Pan Yuhao , Peng Dailiang , Chen Jing M , Myneni Ranga B , Zhang Xiaoyang , Huete Alfredo R , Fu Yongshuo H , Zheng Shijun , Yan Kai , Yu Le , Zhu Peng , Shen Miaogen , Ju Weimin , Zhu Wenquan , Xie Qiaoyun , Huang Wenjiang , Chen Zhengchao , Huang Jingfeng , Wu Chaoyang
Published: April 2023

Global warming has led to earlier spring green-up dates (GUDs) in recent decades with significant consequences for global carbon and hydrologic cycles. In addition to changes in climate, land cover change (LCC), including interchanges between vegetation and non-vegetation, and among plants with different functional traits, may also affect GUD. Here, we analyzed how satellite-derived GUD from 1992 to 2020 was impacted by changes in temperature, precipitation, standardized precipitation evapotranspiration index (SPEI), solar radiation, and LCC for the Northern Hemisphere (>30° N). While the climate variables had larger impact overall, variability in GUD was controlled by LCC for 6% of the Northern Hemisphere, with systematically earlier or later changes among transitions between different land cover types. These changes were found mainly along the southeastern coast of the United States, in Central-north Europe, and across northeastern China. We further showed that climate change attribution of earlier GUD during 1992–2020 was overestimated by three days when the impact of LCC was ignored. Our results deepen the understanding of how LCC impacts GUD variability and enables scientists to more accurately evaluate the impact of climate change on land surface phenology.