bluuebunny/crossref_metadata_2025 huggingface dataset:
Rethinking the image feature biases exhibited by deep convolutional neural network models in image recognition
Authors: Dai Dawei , Li Yutang , Wang Yuqi , Bao Huanan , Wang Guoyin
Published: May 2022

In recent years, convolutional neural networks (CNNs) have been applied successfully in many fields. However, these deep neural models are still considered as “black box” for most tasks. One of the fundamental issues underlying this problem is understanding which features are most influential in image recognition tasks and how CNNs process these features. It is widely believed that CNN models combine low‐level features to form complex shapes until the object can be readily classified, however, several recent studies have argued that texture features are more important than other features. In this paper, we assume that the importance of certain features varies depending on specific tasks, that is, specific tasks exhibit feature bias. We designed two classification tasks based on human intuition to train deep neural models to identify the anticipated biases. We designed experiments comprising many tasks to test these biases in the Res Net and Dense Net models. From the results, we conclude that (1) the combined effect of certain features is typically far more influential than any single feature; (2) in different tasks, neural models can perform different biases, that is, we can design a specific task to make a neural model biased towards a specific anticipated feature.
Stream level rank constrained transceiver design in MIMO interference channel networks
Authors: Zhang Yifei , Zhou Xiaotian , Zhang Haixia , Yuan Dongfeng
Published: May 2022

An interference leakage minimisation transceiver design for multiple‐input multiple‐output Interference Channel networks is proposed by making use of the full rank constraint of the desired signal, the low rank constraint and low power constraint of the interference signal. The objective is to suppress interference leakage caused by not only the signal from other users, but also the other streams from the same user. To do so, the transmit precoding matrix and the receive filtering matrix are iteratively optimised through convex optimisation tools at stream level. Furthermore, a Min–Max interference leakage algorithm is also proposed to suppress the maximum interference from user, with the purpose of guaranteeing the fairness among users. Simulation results demonstrate that taking inter‐stream interference into consideration can significantly improve the effectiveness of multiple‐input multiple‐output Interference Channel networks, while the Min–Max method can slightly increase the system capacity under certain conditions. It can be also confirmed that the trade‐off among effectiveness, fairness and robustness exists in the transceiver optimisation of multiple‐input multiple‐output Interference Channel networks.
Impedance modelling and stability assessment for grid‐connected dual‐PWM adjustable speed drives with motor torque oscillations
Authors: Yang Dirui , Jiang Jianguo
Published: May 2022

The grid‐connected dual‐PWM adjustable speed drives (ASDs) modulate the energy of the motor torque oscillation and inject it into the power system, potentially causing low‐frequency oscillation (LFO) in the grid. In this study, considering the motor torque oscillation and harmonic common‐modulation of the both‐side converters, the precise sequence impedance models are derived for dual‐PWM ASDs using the harmonic linearisation method. Based on the derived impedance of dual‐PWM ASD, the torque oscillation, which is equivalent to the time‐varying impedance, causes a series of discontinuities at the torque‐oscillation‐related frequencies on its amplitude‐frequency curve. Moreover, these discontinuous drops make it more likely to intersect with the amplitude‐frequency curve of the grid impedance, which may lead to LFO of the grid. Then, by applying the proposed impedance model and Bode plot, the stability of the grid‐ASD cascade system with motor torque oscillation is assessed. The conclusions of stability analysis demonstrate the exact mechanism that the mechanical system oscillations lead to the grid‐converter cascade system instability through the common‐modulation and coupling of the dual‐PWM ASD. Finally, experimental results on a 3 kW ASD system in the laboratory and measured results on the distribution grid in the Shanghai Yangshan Deepwater Port area verify the correctness and effectiveness of the proposed model and stability assessment.
A new transformerless quadratic buck–boost converter with high‐voltage gain ratio and continuous input/output current port
Authors: Okati Mustafa , Eslami Mahdiyeh , Jafari Shahbazzadeh Mehdi , Shareef Hussain
Published: May 2022

A new transformerless quadratic buck–boost converter with a common ground and a high‐voltage gain ratio of D/(1−D)2 is proposed in this study. The output and input currents of the proposed structure are continuous due to the presence of inductive filters in the output and input ports. The continuity of the output current simultaneously reduces the voltage ripple and also the capacitor stress at the output port. With the proposed quadratic structure, a lower total switching device power and a higher voltage gain ratio are attained at the same duty cycle. Due to the advantages of the proposed structure, it can be widely used with renewable energy. The presented model is investigated in terms of steady‐state analysis, continuous conduction mode, small‐signal modelling, and efficiency with parasitic resistance effects. To validate the performance of the proposed converter, experiments are conducted in the laboratory to claim the theoretical waveforms obtained from the piecewise linear electrical circuit simulation (PLECS) simulation.
Robust prequalification process of a distribution system operator considering N‐1 contingency
Authors: Jeong Chang Min , Kim Seung Wan , Park Jung Sung , Yoon Yong Tae , Moon Hee Seung
Published: May 2022

A distributed energy resource aggregator (DERA) participates in the wholesale energy market (WEM) on behalf of aggregated distributed renewable energy sources (DRESs). The DERA manages DRESs according to the dispatch signal from the system operator (SO). However, a conventional independent SO that operates the WEM and transmission system does not monitor the distribution system. Therefore, overvoltage or overflow problems can occur during the generation of DRESs in a distribution system in which bids are accepted in the WEM. To address these problems, previous studies proposed the prequalification process. In the process, a distribution SO (DSO), which is responsible for the reliability of the distribution system, reviews DERA's bids before it is submitted to the WEM. However, these studies do not consider the outages of the system components. Therefore, we propose an N‐1 contingency prequalification process (N‐1 PP). The DSO manages the DERA's bid considering both the uncertainties and system states after the reconfiguration in contingency situations. In the proposed scheme, the DERA's bid is reviewed for severe faults and post‐reconfiguration systems. The results indicate that the N‐1 PP is more stable and durable than the prequalification process of previous studies.
Improved power maxima point of photovoltaic system using umbrella optimizing technique under PSCs: An experimental study
Authors: Sharma Amit Kumar , Pachauri Rupendra Kumar , Choudhury Sushabhan , Mahela Om Prakash , Khan Baseem , Gupta Ankur Kumar
Published: May 2022

This paper discusses the umbrella optimizing technique (UOT), a novel approach to track maximum power point (MPP) of a solar photovoltaic (PV) system under partial shading conditions (PSCs).Since PSCs have a direct impact on the power generated by PV modules, many researchers have developed a variety of maximum power point tracking (MPPT) approaches to address this issue. Perturb and Observe (P&O) is a traditional method for tracking the maximum power of a PV module under PSCs. The fundamental issue with this traditional technique is that the algorithm misleads the step size and chases the wrong direction under PSCs to track MPP. The proposed algorithm finds the maximum power peak among several observed peaks caused by partial shading of a PV module. At each instance, the proposed algorithm checks for local or global peaks and adjusts the duty cycle of the inverse SEPIC DC–DC converter accordingly.In experimental study, UOT shows better performance in terms of tracking efficiency, tracking time, output power and output current.It exhibits a power boost of 3.39–4.14% with 9.09–16.66% faster tracking in different PSCs. A comparison of different optimization techniques illustrates that the UOT has higher tracking performance.
Performance evaluation of wireless compressed‐image transmission over discrete Fourier transform‐based orthogonal frequency division multiple access system
Authors: Al‐Ashwal Nagi H. , Al soufy Khaled A. , Al‐Kamali Faisal S. , Swillam Mohamed A.
Published: May 2022

Orthogonal frequency division multiple access (OFDMA) has been attracting much attention in the recent generation of wireless communications to meet the required demands arising from the explosive growth of Internet, multimedia and broadband services. Currently, images transmission is one of the main parts of wireless communication. However, an image file transmission requires sending a large amount of data which consumes a huge bandwidth so that the image must be compressed to reduce the amount of information to be transmitted. The aim of this paper is to evaluate the wireless transmission of the compressed image over discrete Fourier transform (DFT)‐based OFDMA DFT‐OFDMA system for different compression methods, different modulation schemes and different subcarriers mapping schemes over three wireless channels including SUI3, vehicular A and uniform. The required minimum signal‐to‐noise ratio (SNR) to recover the transmitted compressed image is determined to evaluate the system performance. For the sake of diversity, nine compression techniques are used in this work. The MATLAB simulator is used to determine the required minimum SNR to recover the transmitted compressed image for each compression method. The results show that the performance of the set partitioning in hierarchical trees three‐dimensional for true colour images (SPIHT‐3D) method is nearly better than that of other compression methods, especially when the QPSK and interleaved system are considered.
Akute Aortendissektion: Ein lebensbedrohlicher Notfall auch in der
neurologischen Notfallmedizin
Authors: Madlener Marie , Onur Oezguer A. , Müller-Ehmsen Jochen , Fink Gereon R. , Burghaus Lothar
Published: May 2022

Eine akute Aortendissektion ist selten, aber lebensbedrohlich. Die Symptome
hängen von der Lokalisation und Minderperfusion der nachgeschalteten
Organe oder Extremitäten ab und sind dementsprechend variabel. Es
können neurologische Symptome auftreten, die nicht unmittelbar zur
Diagnosestellung führen und so die notwendige Therapie
verzögern. Die Kenntnis der Frühsymptome und Warnsignale einer
Aortendissektion sind deswegen auch in der neurologischen Notfallversorgung
wichtig, um die Betroffenen schnell zu identifizieren und der Akuttherapie
zuzuführen. Eine Fehldiagnose mit verzögerter Therapieeinleitung
kann die Prognose der Patienten deutlich verschlechtern. Ziel dieser Arbeit ist
es, einen standardisierten Diagnostik- und Therapiealgorithmus bei Verdacht auf
eine akute Aortendissektion in der neurologischen Notfallversorgung zu
etablieren. Eine enge interdisziplinärer Zusammenarbeit ist dabei
essentiell.
Risk of recurrence after endoscopic resection of nonpedunculated T1 colorectal cancer
Authors: Arthursson Victoria , Medic Selma , Syk Ingvar , Rönnow Carl-Fredrik , Thorlacius Henrik
Published: May 2022

Background The long-term outcome after local excision of T1 colorectal cancer (CRC) remains unknown. The aim of this study was to examine clinical and histopathological risk factors for recurrence in patients with T1 CRC undergoing endoscopic resection.

Methods This was a retrospective registry-based population study on prospectively collected data of all patients with nonpedunculated T1 CRC undergoing only local excision (no salvage surgery) in Sweden between 2009 and 2018. Potential risk factors for recurrence, including age, sex, tumor location, resection margins, lymphovascular, perineural, and submucosal invasion, grade of differentiation, and mucinous subtype, were analyzed using univariate and multivariate cox regression.

Results Median follow-up time was 60 months, and 28 /602 patients (4.7 %) had a recurrence (13 local and 18 distant). Recurrence rate stratified by submucosal invasion was: Sm1 3.5 % (14 /397), Sm2 6.0 % (8 /133), and Sm3 8.3 % (6 /72), with no significant differences. Resection margins, lymphovascular and perineural invasion, grade of differentiation, mucinous subtype, and age were not significant risk factors for recurrence. In contrast, rectal location was found to be a significant risk factor for tumor recurrence in multivariate analysis (hazard ratio 3.08, P = 0.006). The 3– and 5-year disease-free survival was 96.2 % and 91.1 %, respectively, in T1 CRC patients undergoing endoscopic resection.

Conclusion Tumor recurrence was rare (4.7 %) in this large population-based study on recurrence after local excision of nonpedunculated T1 CRC. Rectal location was an independent risk factor for recurrence, suggesting the need for strict surveillance after endoscopic resection of early rectal cancer.
Recent Developments in Transannular Reactions
Authors: Reyes Efraim , Vicario Jose L. , Prieto Liher , Carrillo Luisa , Uria Uxue
Published: May 2022

Transannular reactions have shown a remarkable performance for the construction of polycyclic scaffolds from medium- or large-sized cyclic molecules in an unconventional manner. Recent examples of transannular reactions reported from 2011 have been reviewed, emphasizing the excellent performance of this approach when accessing the target compounds. This review also highlights how this methodology provides an alternative approach to other commonly used strategies for the construction of cyclic entities such as cyclization or cycloaddition reactions.

1 Introduction

2 Transannular Cycloadditions and Electrocyclizations

3 Transannular Conjugate Additions

4 Transannular 1,2-Addition to Ketones, Imines, Esters, and Amides

5 Transannular Reactions via Electrophilic Activation of Olefins

6 Transannular Ring-Opening of Epoxides

7 Transannular Alkylations of Enolates and Related Species

8 Miscellaneous Transannular Reactions

9 Concluding Remarks
French Athletics Stakeholders’ Perceptions of Relevance and
Expectations on Injury Prevention
Authors: Edouard Pascal , Ruffault Alexis , Bolling Caroline , Navarro Laurent , Martin Simon , Depiesse Frédéric , Oestergaard Nielsen Rasmus , Verhagen Evert
Published: May 2022

This study aimed to explore how stakeholders in athletics perceive the relevance
of injury prevention, determine their communication preferences, and describe
their expectations regarding injury prevention. We conducted a cross-sectional
study using an exploratory online survey with high-level athletes (i. e.
listed by the French ministry of sports), non-high-level athletes (i. e.
all competitive level except high-level athletes), coaches, and health
professionals licensed with the French Federation of Athletics. The survey was
composed of three parts regarding stakeholder’s characteristics (4
questions), perceived relevance (2 questions), communication preferences and
expectations (3 questions) towards injury prevention. There were 2,864
responders to the survey. Almost all responders found that injury prevention is
relevant (97.7% [95% CI 97.0% to 98.2%]),
without any significant differences in the distribution between
stakeholders’ age, experience and sex (p>0.05). About
three-quarters of the stakeholders preferred to find injury prevention
information on a website (77.4%) without significant differences between
stakeholders’ categories (p>0.05); other media to find
injury prevention information was chosen by less than 50% of responders.
Expectations about injury prevention were mainly explanations, advice and tips
about injury knowledge, management and prevention, based on expert opinion
and/or scientific research. In conclusion, these results confirm that
injury prevention is a challenge shared by numerous stakeholders in athletics,
within France, and provide some orientation on how and what information to
disseminate to these stakeholders.
Hemodynamic Response During Different Set Configurations of a
Moderate-load Resistance Exercise
Authors: Rúa-Alonso María , Mayo Xian , Rial-Vázquez Jessica , Fariñas Juan , Aracama Asier , Iglesias-Soler Eliseo
Published: May 2022

We aimed to determine the cardiovascular responses to two different set
configuration resistance-exercise protocols during a knee extension composed of
40 repetitions with a 15RM load and a total resting time of 360 seconds.
Twenty-four healthy sport science students randomly performed two sessions: (a)
a long set configuration (LSC: 4 sets of 10 repetitions with 2 min rest between
sets), and (b) a short set configuration (SSC: 8 sets of 5 repetitions with 51 s
rest between sets). Before and during exercise, peak and mean values of heart
rate, blood pressure, rate pressure product, and pulse pressure were obtained.
Results showed that both protocols increased the overall peak and mean blood
pressure values (p<0.001). However, LSC entailed a higher peak blood
pressure response at the last set (p=0.041) and an increase throughout
the first 30 repetitions (p≤0.007), whereas SSC kept steady after the
first 20 repetitions. Additionally, LSC caused higher overall peak and mean
heart rate and rate pressure product values (p≤0.003). Summarily,
although both protocols raised blood pressure, SSC reduced the extent of the
pressure and chronotropic response during resistance exercise.
Personalbemessung in der Pflege: Mehr Personal für die Pflege in Krankenhäusern
Authors: Heeser Alexandra
Published: May 2022

In der Pflege fehlen Fachkräfte. Die Frage, an der sich bis heute die Geister scheiden, ist, wie das Mehr an Pflegepersonal bemessen werden soll. Es gibt diverse Ansätze für ein Pflegepersonalbemessungsinstrument. Eines ist die PPR 2.0, die jedoch nach wie vor umstritten ist.
Entscheider-Blog: Schluss mit der deutschen Arroganz im Krankenhauswesen!
Authors: Köbe Philipp
Published: May 2022

Die deutsche Kultur des Jammerns, Beklagens, ewig Ausdiskutierens muss endlich enden. Meistens ist jemand anderes Schuld, wenn etwas nicht klappt. Eine außergewöhnliche Geschichte von einem, der dabei nicht mitmachen wollte.
Diversität im Gesundheitswesen: Wertvolle Unterschiede
Authors: Heeser Alexandra , Hohnstein Aileen
Published: May 2022

Was fällt eigentlich alles unter den Begriff Diversity und was ist nötig, um sich in der Arbeitswelt diverser aufzustellen? Ist es nur ein Trend oder ist es sinnvoll, sich als Arbeitgeber dem Thema zu widmen? Reicht es aus, die Charta der Vielfalt zu unterzeichnen? Auf viele dieser Fragen hat die Gesellschaft noch keine Antwort. Dabei geht Diversity uns alle an, auch und besonders in den Krankenhäusern.
Diversität im Gesundheitswesen: „Alle sind einzigartig und damit divers“
Authors: Hohnstein Aileen
Published: May 2022

Maria-Barbara Naumann ist Diversity-Beauftragte und Vorsitzende des neu gegründeten Diversity-Rats bei Vivantes, dem drittgrößten Arbeitgeber Berlins. Warum sie sich für mehr Toleranz und Gleichbehandlung einsetzt, welche Erfolge es in den vergangenen Jahren schon gab und wohin es in Zukunft gehen soll, erzählt sie im Gespräch mit kma.
Patiententransport: Pünktliche Lieferung
Authors: Lang Michael
Published: May 2022

Neuste Software-Systeme steuern den Patiententransport effizienter, indem sie Wegzeiten berechnen, den Transporteur benachrichtigen oder nach bestimmten Kriterien auswählen.
Basic understanding of perovskite solar cells and passivation mechanism
Authors: Yu Yixin , Xia Jingxuan , Liang Yiwen
Published: May 2022

Although perovskite solar cells (PSCs) have made great achievements during the past few years, the efficiency of PSCs is only up to 25.5%, which is comparable to silicon-based solar cells. However, long-term stability is still an important problem for future commercialization. Enormous efforts have been made to prolong the lifetime of PSCs. The novel passivation strategy and advanced encapsulation are investigated, and great achievements are acquired. However, research on the basic understanding of the perovskite structure and the fabrication process of PSCs is rare, which stints the initial research for the abecedarian. At the same time, the defects among the perovskite film caused by the uncontrollable crystallization process and the fragile ionic nature also deteriorate the efficiency and stability of the perovskite devices. Herein, we summarized the investigations of the mechanism for perovskite materials and the manufacturing process of PSCs. The composition of perovskite materials, the orientation of perovskite grain, and various fabrication processes are explained. Simultaneously, the novel passivation strategy and technology are also discussed. We believe that a deeper understanding of the perovskite mechanism is beneficial to render more facilities for further development of perovskite application.
Spectral decimation of a self-similar version of almost Mathieu-type operators
Authors: Mograby Gamal , Balu Radhakrishnan , Okoudjou Kasso A. , Teplyaev Alexander
Published: May 2022

We introduce and study self-similar versions of the one-dimensional almost Mathieu operators. Our definition is based on a class of self-similar Laplacians {Δp}p∈(0,1) instead of the standard discrete Laplacian and includes the classical almost Mathieu operators as a particular case, namely, when the Laplacian’s parameter is p=12. Our main result establishes that the spectra of these self-similar almost Mathieu operators can be described by the spectra of the corresponding self-similar Laplacians through the spectral decimation framework used in the context of spectral analysis on fractals. The spectral-type of the self-similar Laplacians used in our model is singularly continuous when p≠12. In these cases, the self-similar almost Mathieu operators also have singularly continuous spectra despite the periodicity of the potentials. In addition, we derive an explicit formula of the integrated density of states of the self-similar almost Mathieu operators as the weighted pre-images of the balanced invariant measure on a specific Julia set.
Digging deeper: Buried layers and interfaces studied by modified total electron yield and soft x-ray absorption spectroscopy
Authors: Kröger E. , Petraru A. , Hanff A. , Soni R. , Kalläne M. , Denlinger J. D. , Learmonth T. , Guo J.-H. , Smith K. E. , Schneller T. , Freelon B. , Kipp L. , Kohlstedt H. , Rossnagel K. , Kolhatkar G.
Published: May 2022

We report on the soft x-ray absorption spectroscopy investigation of thin film capacitors using a modified total electron yield detection mode. This mode utilizes two ammeters instead of one as commonly employed in the classical total electron yield scheme to measure photocurrents of devices under soft x-ray irradiation. The advantage of this configuration over the surface sensitive classical total electron yield mode is that it can provide information from buried layers and interfaces up to a thickness equal to the penetration depth of soft x-rays. The method can be easily adapted to existing synchrotron end stations. We investigate dielectric capacitors with dissimilar electrodes to assess the feasibility of the modified total electron yield method. Furthermore, in operando soft x-ray absorption spectroscopy measurements are performed on ferroelectric capacitors under bias and using two ammeters. The experimental results are discussed in terms of the external and internal photoemission processes and their distribution in thin film capacitors under an external bias condition. The proposed detection method opens the way to perform electronic and chemical state analyses of the buried interfaces and layers in various devices like multiferroic tunnel junctions, memristive devices, etc., during operation under an applied bias.
Effects of magnetic island on profile formation in flux-driven ITG turbulence
Authors: Muto Mikiya , Imadera Kenji , Kishimoto Yasuaki
Published: May 2022

Full-f gyrokinetic simulations of ion temperature gradient (ITG) turbulence in the presence of a magnetic island are performed. A newly developed method for evaluating the flux-surface average is implemented to treat adiabatic electrons inside the magnetic island precisely. A neoclassical simulation below the threshold for linear ITG instability shows that the density profile does not relax at the O-point, although the ion temperature profile is flattened there. This results from the force balance in the direction of the magnetic field between the pressure gradient related to ion parallel motion and the mean radial electric field. A flux-driven ITG turbulence simulation shows a quasi-periodic transport reduction due to interaction between the background temperature profile and the vortex mode, which is a nonlinearly generated mesoscale structure with the same mode numbers as the magnetic island. These results indicate that not only the parallel streaming but also the equilibrium electric field and turbulence contribute significantly to profile formation around a magnetic island.
Density filamentation nonlinearly driven by the Weibel instability in relativistic beam plasmas
Authors: Huynh Cong Tuan , Ryu Chang-Mo , Kim Chulmin
Published: May 2022

Density filamentation has been observed in many beam-plasma simulations and experiments. Because current filamentation is a pure transverse mode, charge density filamentation cannot be produced directly by the current filamentation process. To explain this phenomenon, several mechanisms are proposed such as the coupling of the Weibel instability to the two-stream instability, coupling to the Langmuir wave, differences in thermal velocities between the beam and return currents, the magnetic pressure gradient force, etc. In this paper, it is shown that the gradient of the Lorentz factor can, in fact, represent the nonlinear behavior of a plasma fluid and further that the nonuniform Lorentz factor distribution can give rise to electrostatic fields and density filaments. Simulation results together with theoretical analyses are presented.
Transition orbital projection approach for excited state tracking
Authors: Du Jiahui , Ma Yixuan , Ma Jing , Li Shuhua , Li Wei
Published: May 2022

Quantitively comparing the features between different electronic excited states (ESs) is a crucial task in both potential energy surface (PES) studies and excited-state fragmentation approaches. However, it is still a challenging problem in regard to the comparison of complex and highly degenerate systems. Herein, we present a transition orbital projection (TOP) method to calculate the similarity of different ESs based on the configuration vectors of two types of transition densities. It fully considers four significant problems, including phase, hole-particle bijectivity, orbital permutation, and sign of configuration coefficients. TOP state-tracking-based excited-state optimization shows high robustness in several high-symmetric systems, which are difficult to describe with traditional state-tracking approaches. The TOP state-tracking method is expected to be widely applied to the PES of photochemical reactions, ES molecular dynamics to track the diabatic states, and fragmentation approaches for local excitation of large systems.
Relaxor-normal ferroelectric transition in (1−x)Sr0.75Ba0.25Nb2O6–xNaNbO3 ceramics
Authors: He Xiao-Juan , Zhang Yi-Chi , Li Ling , Zhang Ji , Gu Zheng-Bin , Zhang Shan-Tao
Published: May 2022

(1−x)Sr0.75Ba0.25Nb2O6–xNaNbO3 (x = 0–0.8) ceramics were prepared by the traditional solid-state reaction method. The x = 0–0.4 ceramics preserve the tungsten bronze phase with a gradually unfilled–filled structure evolution accompanying a relaxor-normal ferroelectric transition. This transition process is accompanied by an increase in the maximum dielectric constant temperature or Curie temperature (Tc), enhancement of room temperature ferroelectric and piezoelectric properties, and appearance of the stripe domain. On the other hand, ceramics with x > 0.4 consist of coexisting tungsten bronze and perovskite phases, for which Tc slightly fluctuates, and the ferroelectric and piezoelectric properties decrease with increasing x. This work provides a feasible way to manipulate the relaxor-normal ferroelectric transition and the electrical properties of the tungsten bronze family.
Machine learning accelerated random structure searching: Application to yttrium superhydrides
Authors: Charraud J.-B. , Geneste G. , Torrent M. , Maillet J.-B.
Published: May 2022

The search for new superhydrides, promising materials for both hydrogen storage and high temperature superconductivity, made great progress, thanks to atomistic simulations and Crystal Structure Prediction (CSP) algorithms. When they are combined with Density Functional Theory (DFT), these methods are highly reliable and often match a great part of the experimental results. However, systems of increasing complexity (number of atoms and chemical species) become rapidly challenging as the number of minima to explore grows exponentially with the number of degrees of freedom in the simulation cell. An efficient sampling strategy preserving a sustainable computational cost then remains to be found. We propose such a strategy based on an active-learning process where machine learning potentials and DFT simulations are jointly used, opening the way to the discovery of complex structures. As a proof of concept, this method is applied to the exploration of tin crystal structures under various pressures. We showed that the α phase, not included in the learning process, is correctly retrieved, despite its singular nature of bonding. Moreover, all the expected phases are correctly predicted under pressure (20 and 100 GPa), suggesting the high transferability of our approach. The method has then been applied to the search of yttrium superhydrides (YHx) crystal structures under pressure. The YH6 structure of space group Im-3m is successfully retrieved. However, the exploration of more complex systems leads to the appearance of a large number of structures. The selection of the relevant ones to be included in the active learning process is performed through the analysis of atomic environments and the clustering algorithm. Finally, a metric involving a distance based on x-ray spectra is introduced, which guides the structural search toward experimentally relevant structures. The global process (active-learning and new selection methods) is finally considered to explore more complex and unknown YHx phases, unreachable by former CSP algorithms. New complex phases are found, demonstrating the ability of our approach to push back the exponential wall of complexity related to CSP.
Deep learning model as an inversion tool for resonant ultrasound spectroscopy of piezoelectric materials
Authors: Yang Wuyi , Sun Shanshan , Hu Jing , Tang Liguo , Qin Lei , Li Zhenglin , Luo Wenyu
Published: May 2022

Device fabrication based on piezoelectric materials requires prior characterization of full matrix constants. For this, the Institute of Electrical and Electronics Engineers standard on piezoelectricity suggests the use of ultrasonic pulse-echo and electric resonance methods. However, these techniques tend to provide inconsistent characterization, because they require multiple samples with drastically different sizes. Resonant ultrasound spectroscopy (RUS) is a promising alternative, because it uses only a single sample for characterization, thus ensuring self-consistent results. The inverse problem of finding material constants from resonant frequencies is often solved using the nonlinear least squares method despite its being a time-consuming algorithm. Herein, deep learning (DL) is introduced in the inversion procedure of RUS. After the DL network is trained, the material constants are determined with high efficiency. The practicability and reliability of the combination of DL and RUS are demonstrated by characterizing the full tensor constants of LiNbO3 single crystals.
Local electronic structure analysis by ab initio elongation method: A benchmark using DNA block polymers
Authors: Orimoto Yuuichi , Hisama Keisuke , Aoki Yuriko
Published: May 2022

The ab initio elongation (ELG) method based on a polymerization concept is a feasible way to perform linear-scaling electronic structure calculations for huge aperiodic molecules while maintaining computational accuracy. In the method, the electronic structures are sequentially elongated by repeating (1) the conversion of canonical molecular orbitals (CMOs) to region-localized MOs (RLMOs), that is, active RLMOs localized onto a region close to an attacking monomer or frozen RLMOs localized onto the remaining region, and the subsequent (2) partial self-consistent-field calculations for an interaction space composed of the active RLMOs and the attacking monomer. For each ELG process, one can obtain local CMOs for the interaction space and the corresponding local orbital energies. Local site information, such as the local highest-occupied/lowest-unoccupied MOs, can be acquired with linear-scaling efficiency by correctly including electronic effects from the frozen region. In this study, we performed a local electronic structure analysis using the ELG method for various DNA block polymers with different sequential patterns. This benchmark aimed to confirm the effectiveness of the method toward the efficient detection of a singular local electronic structure in unknown systems as a future practical application. We discussed the high-throughput efficiency of our method and proposed a strategy to detect singular electronic structures by combining with a machine learning technique.
Reaction processes at step edges on S-decorated Cu(111) and Ag(111) surfaces: MD analysis utilizing machine learning derived potentials
Authors: Liu Da-Jiang , Evans James W.
Published: May 2022

A variety of complexation, reconstruction, and sulfide formation processes can occur at step edges on the {111} surfaces of coinage metals (M) in the presence of adsorbed S under ultra-high vacuum conditions. Given the cooperative many-atom nature of these reaction processes, Molecular Dynamics (MD) simulation of the associated dynamics is instructive. However, only quite restricted Density Functional Theory (DFT)-level ab initio MD is viable. Thus, for M = Ag and Cu, we instead utilize the DeePMD framework to develop machine-learning derived potentials, retaining near-DFT accuracy for the M–S systems, which should have broad applicability. These potentials are validated by comparison with DFT predictions for various key quantities related to the energetics of S on M(111) surfaces. The potentials are then utilized to perform extensive MD simulations elucidating the above diverse restructuring and reaction processes at step edges. Key observations from MD simulations include the formation of small metal–sulfur complexes, especially MS2; development of a local reconstruction at A-steps featuring an S-decorated {100} motif; and 3D sulfide formation. Additional analysis yields further information on the kinetics for metal–sulfur complex formation, where these complexes can strongly enhance surface mass transport, and on the propensity for sulfide formation.
Design and mechanical characteristics research of rock burst prevention combined components of the double laminated springs
Authors: Guo Dongming , Ye Guichuan , Zhao Zhifeng , Lan Fange , Liu Baoyin , Zhang Haotian
Published: May 2022

In order to solve the engineering problem that the bolt tail is often broken under the impact of rock pressure, mining stress and the damage to the support structure contribute to great hidden danger to the safety of mining and tunneling. A new anti-impact bolt support structure is designed that can absorb energy under pressure. The double laminated springs and the inner spring deform under the impact load to achieve the purpose of absorbing most of the impact energy. The composition and working principle of the energy-absorbing structure is introduced. The static axial compression tests of the single laminated springs with cone angles of 30°, 45°, and 60° are carried out. The mechanical characteristics of the laminated springs in the three stages of energy absorption are investigated. It is found that the 45° laminated spring has the best energy absorption effect. The simulation method was used to analyze and optimize the energy absorption effect of anti-scour composite components. Double laminated spring anti-shock composite components absorb the impact energy and avoid the damage to the bolt support structure, which reduces the roadway support cost and has important engineering application value for ensuring the safety of deep tunneling and mining.
Phonon transport properties of particulate physical gels
Authors: Mizuno Hideyuki , Hachiya Makoto , Ikeda Atsushi
Published: May 2022

Particulate physical gels are sparse, low-density amorphous materials in which clusters of glasses are connected to form a heterogeneous network structure. This structure is characterized by two length scales, ξs and ξG: ξs measures the length of heterogeneities in the network structure and ξG is the size of glassy clusters. Accordingly, the vibrational states (eigenmodes) of such a material also exhibit a multiscale nature with two characteristic frequencies, ω* and ωG, which are associated with ξs and ξG, respectively: (i) phonon-like vibrations in the homogeneous medium at ω<ω*, (ii) phonon-like vibrations in the heterogeneous medium at ω*<ω<ωG, and (iii) disordered vibrations in the glassy clusters at ω > ωG. Here, we demonstrate that the multiscale characteristics seen in the static structures and vibrational states also extend to the phonon transport properties. Phonon transport exhibits two distinct crossovers at frequencies ω* and ωG (or at wavenumbers of ∼ξs−1 and ∼ξG−1). In particular, both transverse and longitudinal phonons cross over between Rayleigh scattering at ω<ω* and diffusive damping at ω>ω*. Remarkably, the Ioffe–Regel limit is located at the very low frequency of ω*. Thus, phonon transport is localized above ω*, even where phonon-like vibrational states persist. This markedly strong scattering behavior is caused by the sparse, porous structure of the gel.
The nuclear-spin-forbidden rovibrational transitions of water from first principles
Authors: Yachmenev Andrey , Yang Guang , Zak Emil , Yurchenko Sergei , Küpper Jochen
Published: May 2022

The water molecule occurs in two nuclear-spin isomers that differ by the value of the total nuclear spin of the hydrogen atoms, i.e., I = 0 for para-H2O and I = 1 for ortho-H2O. Spectroscopic transitions between rovibrational states of ortho and para water are extremely weak due to the tiny hyperfine nuclear-spin–rotation interaction of only ∼30 kHz and, so far, have not been observed. We report the first comprehensive theoretical investigation of the hyperfine effects and ortho–para transitions in H216O due to nuclear-spin–rotation and spin–spin interactions. We also present the details of our newly developed general variational approach to the simulation of hyperfine effects in polyatomic molecules. Our results for water suggest that the strongest ortho–para transitions with room-temperature intensities on the order of 10−31 cm/molecule are about an order of magnitude larger than previously predicted values and should be detectable in the mid-infrared ν2 and near-infrared 2ν1 + ν2 and ν1 + ν2 + ν3 bands by current spectroscopy experiments.
Spatiotemporal optimization on cross correlation for particle image velocimetry
Authors: Xie Zongming , Wang Hongping , Xu Duo
Published: May 2022

We introduce an optimization method for the cross-correlation operation in particle image velocimetry by locating the correlation peaks assisted with constraint conditions. In this study, an objective function was constructed to include the residual of the normalized cross-correlation term, a component in charge of spatial smoothness (inspired by the optical flow method as used in a previous study) and a component for temporal smoothness (inspired by the concept of trajectory selection in particle tracking velocimetry). Minimizing the objective function gives optimized velocity fields for a series of tracer images for spatiotemporal smoothness. The proposed method was examined in synthetic images of turbulent flow and Batchelor vortex and in a laboratory experiment of vortex rings. The effect of image background noises and the initial guess for the optimization process were examined and discussed.
Effects of temperature and oxygen partial pressure on electrical conductivity of Fe-doped β-Ga2O3 single crystals
Authors: Ryu Gyunghyun , Reddy Pramod , Collazo Ramón , Dickey Elizabeth C.
Published: May 2022

In this work, we measure DC and AC conductivity and Hall voltage to determine the origin of electrical insulating properties of Fe-doped β-Ga2O3 single crystals, which are measured perpendicular to the 2¯01 crystallographic plane. We find that electrical conduction is predominantly controlled by free electrons in the temperature range 230–800 °C with the mutual compensation of the impurity donor (Si) and acceptor dopant (Fe), explaining the low concentration of free electrons and Fermi level pinning over a wide range of temperatures. Furthermore, the negative temperature-dependence of the carrier mobility indicates that it is limited by optical phonon scattering. Importantly, we find electrical conductivity to be largely independent of oxygen partial pressure (pO2) from air to 10−4 atm at 600 °C, but it becomes slightly dependent on pO2 at 800 °C, as intrinsic non-stoichiometric point defects begin to influence the charge balance.
Size-selective predation by three estuarine zooplanktivorous fish species
Authors: Schilling Hayden T. , Smith James A. , Everett Jason D. , Harrison Daniel P. , Suthers Iain M.
Published: May 2022

Context Zooplanktivorous fish are a key link between abundant zooplankton and higher trophic levels but the foraging behaviour of zooplanktivorous fish is not fully understood. Selective feeding behaviours have been observed, with many species of planktivorous fish targeting certain species and sizes of zooplankton for prey. However, why certain size classes of zooplankton are preferred remains unclear. Aim This study investigated prey selection by three zooplanktivorous fish species through the lens of optimal foraging theory. Methods We assessed the size structure of zooplankton in the environment and compared this with the size distribution of zooplankton in gut contents from three zooplanktivorous fish. Key results The targeted prey size of Atypichthys strigatus and Scorpis lineolata aligns with the prey size classes in the environment that contain the highest overall biomass. Trachurus novaezelandiae showed little evidence of targeting these size classes. Conclusions These prey sizes therefore represent the most efficient prey to target because the return on foraging effort is greatest. By contrast, T. novaezelandiae showed only an underselection of large and small prey. Implications By incorporating this information on this key trophic link between zooplankton and fish, ecosystem models could better resolve the size dependant predation, particularly in size-based models.
Mosquito-borne diseases.
Authors: Catry Thibault , Vignolles Cécile , Kotchi Serge Olivier , Brazeau Stéphanie , Ludwig Antoinette , Ogden Nicholas H. , Bicout Dominique J. , Fournier Richard A. , Werle Dirk
Published: May 2022

The World Health Organization (WHO) has highlighted identification and monitoring of vector populations as an important component of global vector-borne disease surveillance efforts. EO and RVF map data could play a crucial role in identifying risk locations for mosquito-borne diseases globally on the basis of habitat and climate variables. EO and RVF map data are also useful for measuring or mapping a range of environmental parameters that help determine mosquito vector occurrence and abundance and the rate of development of mosquito-borne parasites and pathogens in mosquito vectors. The EO and RVF map data have been sufficiently high spatial and temporal resolution, applied research could develop weather-based and environment-based forecasting of high-risk locations and time periods for mosquito-borne diseases using statistical models. The maps generated by this project indicate and outline the RVF risk areas associated with surface water ponding, mosquito breeding, and cattle grazing for a test area in Senegal. This strategy could include the following recommendations to effectively mitigate the exposure of cattle to RVF, and thus to minimise infection risk for humans: establish a joint communication strategy by integrating information of the forecasted risk bulletins into the National Information System of Surveillance of Epidemics used by the Ministry of Livestock in Senegal and the Headquarters of the Directorate of Veterinary Services of Senegal and its local representatives in rural districts, relocate livestock grazing areas away from risk zones, with warning signs in local languages posted near the ponds to inform breeders to keep their animals at least 500 m away from the ponds, and issue regular bulletins so the Directorate of Veterinary Services of Senegal can organise and optimise vaccination campaigns in the riskiest zones.
Needs, challenges, and opportunities: a review by experts.
Authors: Brazeau Stéphanie , Vignolles Cécile , Krishnamurthy Ramesha S. , Trtanj Juli , Haynes John , Ramage Steven , Catry Thibault , Kotchi Serge Olivier , Borderon Marion , Gill Michael , Ogden Nicholas H. , Ludwig Antoinette , Aube Guy , Semenza Jan C. , Trinanes Joaquin , Davignon Didier
Published: May 2022

This book chapter discusses all the information collected has been grouped together into eight categories: (i) aligning with and supporting UN Sustainable Development Goals; (ii) focusing on public health needs and key theme areas for further research; (iii) accessing and developing Earth Observation (EO) and geospatial evidence-based data and products leveraging public health capacities; (iv) developing a sustainable community of practice; (v) developing knowledge and know-how; (vi) developing solutions: methods, tools, and systems; (vii) implementing technical infrastructures and technologies; and (viii) participating in EO satellite mission development for monitoring disease risks. One such advancement attributable to Landsat data is the ability to monitor changing patterns in forest cover loss and human encroachment on previously wild areas that allows for better prediction of zoonotic disease emergence. For example, the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the US Aqua and Terra satellites offer atmosphere, land, cryosphere, and ocean products that are used in several user communities. MODIS indicator data sets have been so successful that they do not require additional remote sensing analysis; they can be used directly in predictive models. Some EO satellite systems offer ARD (i.e. pre-processed images) and related information products derived from the raw data stream generated by the satellite instruments and the use of algorithms.