bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, mortality, and reproduction of the oblique-banded snapper (
Authors: Schemmel Eva , Nichols Ryan , Cruz Eric , Boyer Jane F. F. , Camacho Frank A.
Published: December 2021

Deep-water snapper fisheries in the Mariana Archipelago are important commercial, recreational and subsistence fisheries. Pristipomoides zonatus, one of the top four deep-water snapper species harvested in Guam, lacked life-history information. To fill this gap, a comprehensive life-history assessment for P. zonatus, which included age, growth, mortality and reproduction, was conducted in Guam. The size range of P. zonatus sampled for life history was from 11.5 cm to 40.4 cm (fork length), with ages ranging from 0.5 to 30 years. Von Bertalanffy growth model-combined sex parameters were L∞ = 36.91 cm and K = 0.29. Males obtained a larger average size and a larger asymptotic size (+3.03 cm) than did females. Pristipomoides zonatus matures at a small size and age (L50 ≤ 24.0 cm and A50 ≤ 2.1 years) relative to their maximum size (40.4 cm) and age (30 years). Additionally, P. zonatus has a long spawning season and a short spawning interval, suggesting high reproductive output. Our results expand knowledge on Pristipomoides life history (fast early growth, moderately long-lived, high productivity), providing the necessary information for the management of P. zonatus in Guam.
Receptive academic vocabulary knowledge and extramural English involvement – is there a correlation?
Authors: Warnby Marcus
Published: December 2021

Extramural English (EE) exposure has been shown to correlate with general vocabulary knowledge. It remains uncertain, however, how academic vocabulary knowledge correlates with EE and can be explained by EE factors and demographic factors. Therefore, an academic vocabulary test, a background questionnaire, and a survey on current EE involvement were administered to 817 Swedish upper-secondary students in university-preparatory study programmes. A linear model revealed little explanation from demographic factors (age, gender, number of first languages, length of English instruction, and parental educational level) whereas EE factors (reading, listening & viewing without textual support, viewing with Swedish subtitles) accounted for 26% of the variation. Since extensive EE involvement may support the incidental learning of academic lexis, the paper suggests pre-tertiary instructional principles being guided by extramural as well as intramural incidental learning opportunities.
On the dialogic frames of mirative enunciations
Authors: García Negroni María Marta , Libenson Manuel
Published: December 2021

In this paper we will describe the meanings of surprise associated to different uses of the discourse marker
mirá in Argentinian Spanish. Our aim is to contrast the subjective stances of surprise emerging in response to the
different dialogic frames prompting mirative enunciations with mirá. From the Dialogic Approach to Argumentation and
Polyphony, we intend to show how these stances of surprise can be explained as dialogically “caused” by the argumentative representation of:
(a) a sudden discovery that brings out something new, (b) a sudden discovery related to something that contradicts a previous belief or
assumption and (c) a sudden discovery of something that exceeds its ordinary magnitude or degree.
Laser pressure welding of dissimilar aluminium and copper: microstructure and mechanical property
Authors: Zhang Jingquan , Guo Shihui , Wang Dong , Xu Jiejie , Huang Ting , Xiao Rongshi
Published: December 2021

In this work, laser pressure welding of dissimilar aluminium and copper was conducted at a high welding speed of 15 m min−1. One-micron intermetallic compounds (IMCs) layer with heterogeneous dual-phases (copper and γ-Al4Cu9 phases) laminates in the joint interface were observed by transmission electron microscopy. The results showed that the combination of two joining mechanisms led to improved mechanical property, namely the mechanical interlocking due to the curved interface and the metallurgical bonding by the presence of the thin IMCs layer with heterogeneous laminates. The tensile shear force and the shear strength of the joint reached 2055 N and 111.94 MPa, respectively. The present study provides a more efficient method to join dissimilar aluminium and copper.
Variational approach to the Schrödinger equation with a delta-function potential
Authors: Fernández Francisco M
Published: December 2021

We obtain accurate eigenvalues of the one-dimensional Schrödinger equation with a Hamiltonian of the form H

g
= H + gδ(x), where δ(x) is the Dirac delta function. We show that the well known Rayleigh–Ritz variational method is a suitable approach provided that the basis set takes into account the effect of the Dirac delta on the wavefunction. Present analysis may be suitable for an introductory course on quantum mechanics to illustrate the application of the Rayleigh–Ritz variational method to a problem where the boundary conditions play a relevant role and have to be introduced carefully into the trial function. Besides, the examples are suitable for motivating the students to resort to any computer-algebra software in order to calculate the required integrals and solve the secular equations.
Conforming and nonconforming finite element methods for biharmonic inverse source problem
Authors: Nair M Thamban , Shylaja Devika
Published: December 2021

This paper deals with the numerical approximation of the biharmonic inverse source problem in an abstract setting in which the measurement data is finite-dimensional. This unified framework in particular covers the conforming and nonconforming finite element methods (FEMs). The inverse problem is analysed through the forward problem. Error estimate for the forward solution is derived in an abstract set-up that applies to conforming and Morley nonconforming FEMs. Since the inverse problem is ill-posed, Tikhonov regularization is considered to obtain a stable approximate solution. Error estimate is established for the regularized solution for different regularization schemes. Numerical results that confirm the theoretical results are also presented.
Easy-cone state in spin-torque diode under combined action of magnetostatics and perpendicular anisotropy
Authors: Buzdakov A G , Skirdkov P N , Zvezdin K A
Published: December 2021

Spin-torque diodes (STDs) with interfacial perpendicular magnetic anisotropy (IPMA) in the free layer (FL) demonstrate outstanding microwave signal rectification performances. Large sensitivity values in such systems are usually associated with an easy-cone (EC) magnetic state, when the magnetization in the FL is tilted from the normal to the plane of the film. Here, we theoretically investigate the phase diagram for the EC state in an infinite FL of the magnetic tunnel junction (MTJ) considering both IPMA (of the first and of the second order) and magnetostatic interaction. We show that the increase of the magnetostatic field leads to the EC state phase expansion. For elliptical MTJ nanopillars we investigate the influence of the orientation of the nanopillar ellipticity on the obtained phase diagrams. And finally, we consider the dynamic properties and rectification efficiency of the STD under microwave current injection. Our results clarify the role of magnetostatic interaction for microwave rectification with the IPMA-based STDs and suggest approaches to the EC state effective rectification phase extension through the parameters optimization.
Broadband excitation of spin wave using microstrip line antennas for integrated magnonic devices
Authors: Mori Kanta , Goto Taichi , Watanabe Toshiaki , Koguchi Takumi , Nakamura Yuichi , Lim Pang Boey , Ustinov Alexey B , Inoue Mitsuteru
Published: December 2021

Strong- and broadband-spin wave (SW) excitation/detection structures are useful for magnonic devices. In particular, such structures are essential for observing magnonic bandgaps of magnonic crystals (MCs). Therefore, this study proposes a manufacturable broadband-SW excitation/detection antenna structure suitable for evaluating MCs. The antenna structure comprises a microstrip line fabricated on a yttrium iron garnet on a metal-covered silicon substrate. Calculations were performed using a three-dimensional finite integration technique and dispersion curves of SWs. The proposed structure exhibited high performance because of the significantly short distance between the signal line and ground plane. The generated bandwidth was ∼1.69 GHz for the 8.9 μm-wavelength SW at a frequency of 4 GHz. This work proposed an appropriate antenna structure for observing magnonic bandgaps, showing high potential for the development of MCs in integrated SW devices.
Observation of giant exchange bias effect in Ni–Mn–Ti all-d-metal Heusler alloy
Authors: Samanta Saheli , Ghosh Subrata , Mandal Kalyan
Published: December 2021

We report a giant exchange bias (EB) field of about 3.68 kOe during field cooled process in all-d-metal Ni40(FeCo)4Mn36Ti20 Heusler alloy. The study of magnetic memory effect and isothermal magnetic relaxation processes suggest that the giant EB field arises due to the possible coexistence of antiferromagnetic (AFM) and ferromagnetic (FM) phase exchange interaction in the studied system at temperatures below 35 K. Furthermore, the temperature and cooling field dependence of EB effect are analyzed which are related to the change in unidirectional anisotropy at FM/AFM interface. The study of a well-established training effect confirms the intrinsic nature of the observed EB behavior. This result will open up a new way toward the development of EB materials considering all-d-metal Heusler alloy systems.
Making high-quality quantum microwave devices with van der Waals superconductors
Authors: Antony Abhinandan , Gustafsson Martin V , Rajendran Anjaly , Benyamini Avishai , Ribeill Guilhem , Ohki Thomas A , Hone James , Fong Kin Chung
Published: December 2021

Ultra low-loss microwave materials are crucial for enhancing quantum coherence and scalability of superconducting qubits. Van der Waals (vdW) heterostructure is an attractive platform for quantum devices due to the single-crystal structure of the constituent two-dimensional (2D) layered materials and the lack of dangling bonds at their atomically sharp interfaces. However, new fabrication and characterization techniques are required to determine whether these structures can achieve low loss in the microwave regime. Here we report the fabrication of superconducting microwave resonators using NbSe2 that achieve a quality factor Q > 105. This value sets an upper bound that corresponds to a resistance of

⩽
192

μ
Ω

when considering the additional loss introduced by integrating NbSe2 into a standard transmon circuit. This work demonstrates the compatibility of 2D layered materials with high-quality microwave quantum devices.
Two-step Brillouin zone sampling for efficient computation of electron dynamics in solids
Authors: Sato Shunsuke A
Published: December 2021

We develop a numerical Brillouin-zone integration scheme for real-time propagation of electronic systems with time-dependent density functional theory. This scheme is based on the decomposition of a large simulation into a set of small independent simulations. The performance of the decomposition scheme is examined in both linear and nonlinear regimes by computing the linear optical properties of bulk silicon and high-order harmonic generation. The decomposition of a large simulation into a set of independent simulations can improve the efficiency of parallel computation by reducing communication and synchronization overhead and enhancing the portability of simulations across a relatively small cluster machine.
Modifying Jahn–Teller distortion by epitaxial stress in LaMnO3 films for tunning electron localization
Authors: Chen Xin , Wang Baohua , Ge Tongxin , Wei Haoming , Cao Bingqiang
Published: December 2021

The effect of epitaxial stress on Jahn–Teller (JT) distortion in epitaxial LaMnO3 (LMO) films has been investigated. Both 2θ–ω scans and reciprocal space maps (RSMs) indicate that LMO samples are subjected to compressive stress. Obvious Laue oscillations can be detected in 2θ–ω scans, indicating the high quality of samples. RSMs of symmetry peak (001) and asymmetry peak (−103) imply different epitaxial stress for LMO films deposited on different substrates. Raman spectra measurements reveal that the degree of JT distortion can be well tuned via the epitaxial stress which may further influence on the electron localization in the films. This study might benefit to understanding the correlation between crystalline structure and electrical transport properties of LMO films and related LMO-based superlattices.
Minimum settings calibration method for low-cost tri-axial IMU and magnetometer
Authors: Chao Cui , Zhao Jiankang , Zhu Jianbin , Bessaad Nassim
Published: December 2021

This manuscript presents a minimum settings calibration method for low-cost tri-axial inertial measurement units (IMUs) and magnetometers. At first, we analyze the major defect of the traditional calibration methods for tri-axial accelerometers and magnetometers. To fix that problem, we utilize the ellipsoid model to calibrate the tri-axial accelerometer and magnetometer preliminarily, then complete the calibration work with at least two reference angular positions, and prove that two reference angular positions are minimum requirements in the calibration progress. Next, the tri-axial gyroscope is calibrated based on the nonlinear cost function with the aid of the pre-calibrated accelerometer. The simulation and real-world experiment results show that the proposed method is practical and effective, suggesting that this technique is a viable candidate for the applications that require IMUs and magnetometers.
The strong interfacial coupling effect of Nafion between LaFeO3/electrolyte for efficient photoelectrochemical water reduction
Authors: Ding Xinran , Chen Tong , He Yanfang , Zhu Jianfei , Yang Ying , Chen Jie , Nasori Nasori , Liu Yuan , Chen Mingming , Cao Dawei
Published: December 2021

Insufficient reduction capability and scanty active substance limit the application of LaFeO3 (LFO) in the field of photoelectrochemical (PEC) water splitting. This work demonstrates a judicious combination of LFO/Nafion composite to improve the PEC performance by a unique dip-coating method on the FTO. The photocurrent density of the LFO electrode coated with two layers Nafion increased to −23.9 μA cm−2 at 0.47 V versus RHE, which is 4.1 times that of the pristine LFO. Based on the experimental data and theoretical analysis, the improvement of the PEC properties is attributed to the construction of organic/inorganic units, which would enable strong electronic coupling and favor interfacial charge transfer, resulting in a 30 mV downward shift of its flat band potential. Thus, the conduction band gets closer to the proton reduction potential of H+ to H2 after decoration with Nafion, resulting in a stronger photogenerated electron reduction ability. Our study provides insights that organic materials modify semiconductor photoelectrodes for accelerating charge kinetics.
Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping
Authors: Wang Liushun , Li Dong , Zhou Yulan , Fu Shaohua , Peng Yuehua , Yin Yanling , Wang Weike , Zhou Weichang , Tang Dongsheng
Published: December 2021

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO6 octahedra by the addition of edge-sharing NbO6 octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb2O5·15WO3 nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb2O5·15WO3 nanowires do exhibit more advantages over h-WO3 nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g−1, at 10C, 1C = 100 mA g−1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H+ ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO3. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.
Interparticle gap geometry effects on chiroptical properties of plasmonic nanoparticle assemblies
Authors: Li Feng , Chandrasekar Skandan , Ahmed Aftab , Klinkova Anna
Published: December 2021

Chiral linear assemblies of plasmonic nanoparticles with chiral optical activity often show low asymmetry factors. Systematic understanding of the structure-property relationship in these systems must be improved to facilitate rational design of their chiroptical response. Here we study the effect of large area interparticle gaps in chiral linear nanoparticle assemblies on their chiroptical properties using a tetrahelix structure formed by a linear face-to-face assembly of nanoscale Au tetrahedra. Using finite-difference time-domain and finite element methods, we performed in-depth evaluation of the extinction spectra and electric field distribution in the tetrahelix structure and its dependence on various geometric parameters. The reported structure supports various plasmonic modes, one of which shows a strong incident light handedness selectivity that is associated with large face-to-face junctions. This works highlights the importance of gap engineering in chiral plasmonic assemblies to achieve g-factors greater than 1 and produce structures with a handedness-selective optical response.
Carbon nanotubes as electronic mediators combined with Bi2MoO6 and g-C3N4 to form Z-scheme heterojunctions to enhance visible light photocatalysis
Authors: Wu Hao , Meng Fanming , Liu Xingbing , Yu Bo
Published: December 2021

In this paper, Z-scheme Bi2MoO6/CNTs/g-C3N4 composite photocatalysts were prepared through a simple hydrothermal method. The analysis was performed by XRD, FT-IR, SEM, EDS, TEM, HRTEM, XPS, BET, UV–Vis diffuse reflectance and PL spectrums. Various analyses show that CNTs not only act as excellent charge transfer bridges, but also enable a formation of the Z-scheme of charge transfer mechanism between Bi2MoO6 and g-C3N4. This process not only effectively isolates electrons and holes, but also prolongs electron–hole pair lifetimes, resulting in a substantial improvement in the photocatalytic performance of the composite photocatalyst. Best photocatalytic degradation performance was shown by Bi2MoO6/CNTs/g-C3N4 composite photocatalyst under simulated sunlight, while the composite photocatalyst still maintained extremely high degradation performance in cycling tests.
Gradient coil and radiofrequency induced heating of orthopaedic implants in MRI: influencing factors
Authors: Wooldridge J , Arduino A , Zilberti L , Zanovello U , Chiampi M , Clementi V , Bottauscio O
Published: December 2021

Patients with implanted orthopaedic devices represent a growing number of subjects undergoing magnetic resonance imaging (MRI) scans each year. MRI safety labelling is required for all implants under the EU Medical Device Regulations to ensure regulatory compliance, with each device assessed through standardised testing procedures. In this paper, we employ parametric studies to assess a range of clinically relevant factors that cause tissue heating, performing simulations with both radiofrequency (RF) and gradient coil (GC) switching fields, the latter of which is often overlooked in the literature. A series of ‘worst-case’ scenarios for both types of excitation field is discussed. In the case of GC fields, large volume implants and large plate areas with the field orientated perpendicular to the plane cause the highest heating levels, along with sequences with high rates of field switching. Implant heating from RF fields is driven primarily from the ‘antenna effect’, with thin, linear implants of resonant length resulting in the highest temperature rises. In this work, we show that simplifications may be made to the field sequence and in some cases the device geometry without significantly compromising the accuracy of the simulation results, enabling the possibility for generic estimates of the implant heating for orthopaedic device manufacturers and opportunities to simplify the safety compliance process.
Impact of image pre-processing methods on computed tomography radiomics features in chronic obstructive pulmonary disease
Authors: Au Ryan C , Tan Wan C , Bourbeau Jean , Hogg James C , Kirby Miranda
Published: December 2021

Computed tomography (CT) imaging texture-based radiomics analysis can be used to assess chronic obstructive pulmonary disease (COPD). However, different image pre-processing methods are commonly used, and how these different methods impact radiomics features and lung disease assessment, is unknown. The purpose of this study was to develop an image pre-processing pipeline to investigate how various pre-processing combinations impact radiomics features and their use for COPD assessment. Spirometry and CT images were obtained from the multi-centered Canadian Cohort of Obstructive Lung Disease study. Participants were divided based on assessment site and were further dichotomized as No COPD or COPD within their participant groups. An image pre-processing pipeline was developed, calculating 32 grey level co-occurrence matrix radiomics features. The pipeline included lung segmentation, airway segmentation or no segmentation, image resampling or no resampling, and either no pre-processing, binning, edgmentation, or thresholding pre-processing techniques. A three-way analysis of variance was used for method comparison. A nested 10-fold cross validation using logistic regression and multiple linear regression models were constructed to classify COPD and assess correlation with lung function, respectively. Logistic regression performance was evaluated using the area under the receiver operating characteristic curve (AUC). A total of 1210 participants (Sites 1–8: No COPD: n = 447, COPD: n = 413; and Site 9: No COPD: n = 155, COPD: n = 195) were evaluated. Between the two participant groups, at least 16/32 features were different between airway segmentation/no segmentation (P ≤ 0.04), at least 29/32 features were different between no resampling/resampling (P ≤ 0.04), and 32/32 features were different between the pre-processing techniques (P < 0.0001). Features generated using the resampling/edgmentation and resampling/thresholding pre-processing combinations, regardless of airway segmentation, performed the best in COPD classification (AUC ≥ 0.718), and explained the most variance with lung function (R
2 ≥ 0.353). Therefore, the image pre-processing methods completed prior to CT radiomics feature extraction significantly impacted extracted features and their ability to assess COPD.
Generalized deep iterative reconstruction for sparse-view CT imaging
Authors: Su Ting , Cui Zhuoxu , Yang Jiecheng , Zhang Yunxin , Liu Jian , Zhu Jiongtao , Gao Xiang , Fang Shibo , Zheng Hairong , Ge Yongshuai , Liang Dong
Published: December 2021

Sparse-view CT is a promising approach for reducing the x-ray radiation dose in clinical CT imaging. However, the CT images reconstructed from the conventional filtered backprojection algorithm suffer from severe streaking artifacts. Iterative reconstruction algorithms have been widely adopted to mitigate these streaking artifacts, but they may prolong the CT imaging time due to the intense data-specific computations. Recently, a model-driven deep learning CT image reconstruction method, which unrolls the iterative optimization procedures into a deep neural network, has shown exciting prospects for improving image quality and shortening the reconstruction time. In this work, we explore a generalized unrolling scheme for such an iterative model to further enhance its performance on sparse-view CT imaging. By using it, the iteration parameters, regularizer term, data-fidelity term and even the mathematical operations are all assumed to be learned and optimized via network training. Results from the numerical and experimental sparse-view CT imaging demonstrate that the newly proposed network with the maximum generalization provides the best reconstruction performance.
Sex differences in muscle excitation and oxygenation, but not in force fluctuations or active hyperemia resulting from a fatiguing, bilateral isometric task
Authors: Keller Joshua L , Anders John Paul V , Neltner Tyler J , Housh Terry J , Schmidt Richard J , Johnson Glen O
Published: December 2021

It remains to be fully elucidated if there are sex-specific physiological adjustments within the human neuromuscular and vascular systems that contribute to symptoms of fatigue during a sustained bilateral task. This, in part, is likely due to various limitations in experimental design such as an inability to independently record force fluctuations from each limb. Objective. Therefore, the purpose of the current study was to examine the fatigue-induced changes in muscle excitation, force fluctuations, skeletal muscle tissue saturation (StO2), and muscle blood flow resulting from a sustained, bilateral task. Approach. Thirty healthy, college-aged adults (15 males, 15 females) performed a bilateral leg task at 25% of maximum voluntary isometric (MVIC). Before and after the task, MVICs were completed. Resting and post-task femoral artery blood flow (FABF) were determined. Muscle excitation was quantified as electromyographic amplitude (EMG AMP) from the right and left vastus lateralis. During the task, force fluctuations were determined independently from each leg. The StO2 signal was collected with a near-infrared spectroscopy device attached to the right vastus lateralis. The rate of change in these variables was calculated via simple linear regression. The exercise-induced magnitude of change in MVIC (i.e. performance fatigability) and FABF (i.e. active hyperemia) was determined. Main Results. There was no sex difference in the percent decline in MVIC (20.5 ± 20.1% versus 16.4 ± 3.5%; p > 0.05). There were no inter-leg differences in EMG AMP or force fluctuations. The males exhibited a faster rate of increase in EMG AMP (b = 0.13 versus b = 0.08; p < 0.001), whereas the females exhibited a slower rate of decline in StO2 (b = −0.049 versus b = −0.080). There was no sex difference in force fluctuations or change in FABF. Significance. Males and females likely have different neuromuscular strategies and muscle characteristics, but these did not elicit a sex difference in performance fatigability.
Vascular ageing and peripheral pulse: an improved model for assessing their relationship
Authors: Aliani Cosimo , Rossi Eva , Francia Piergiorgio , Bocchi Leonardo
Published: December 2021

Objective. Vascular ageing is associated with several alterations, including arterial stiffness and endothelial dysfunction. Such alterations represent an independent factor in the development of cardiovascular disease (CVD). In our previous works we demonstrated the alterations occurring in the vascular system are themselves reflected in the shape of the peripheral waveform; thus, a model that describes the waveform as a sum of Gaussian curves provides a set of parameters that successfully discriminate between under (≤35 years old) and over subjects (>35 years old). In the present work, we explored the feasibility of a new decomposition model, based on a sum of exponential pulses, applied to the same problem. Approach. The first processing step extracts each pulsation from the input signal and removes the long-term trend using a cubic spline with nodes between consecutive pulsations. After that, a Least Squares fitting algorithm determines the set of optimal model parameters that best approximates each single pulse. The vector of model parameters gives a compact representation of the pulse waveform that constitutes the basis for the classification step. Each subject is associated to his/her ‘representative’ pulse waveform, obtained by averaging the vector parameters corresponding to all pulses. Finally, a Bayesan classifier has been designed to discriminate the waveforms of under and over subjects, using the leave-one-subject-out validation method. Main results. Results indicate that the fitting procedure reaches a rate of 96% in under subjects and 95% in over subjects and that the Bayesan classifier is able to correctly classify 91% of the subjects with a specificity of 94% and a sensibility of 84%. Significance. This study shows a sensible vascular age estimation accuracy with a multi-exponential model, which may help to predict CVD.
Robust wave-feature adaptive heartbeat classification based on self-attention mechanism using a transformer model
Authors: Hu Shuaicong , Cai Wenjie , Gao Tijie , Zhou Jiajun , Wang Mingjie
Published: December 2021

Objective. Electrocardiography is a common method for screening cardiovascular diseases. Accurate heartbeat classification assists in diagnosis and has attracted great attention. In this paper, we proposed an automatic heartbeat classification method based on a transformer neural network using a self-attention mechanism. Approach. An adaptive heartbeat segmentation method was designed to selectively focus on the time-dependent representation of heartbeats. A one-dimensional convolution layer was used to embed wave characteristics into symbolic representations, and then, a transformer block using multi-head attention was applied to deal with the dependence of wave-embedding. The model was trained and evaluated using the MIT-BIH arrhythmia database (MIT-DB). To improve the model performance, the model pre-trained on MIT-BIH supraventricular arrhythmia database (MIT-SVDB) was used and fine-tuned on MIT-DB. Main results. The proposed method was verified using the MIT-DB for two groups. In the first group, our method attained F1 scores of 0.86 and 0.96 for the supraventricular ectopic beat class and ventricular ectopic beat class, respectively. In the second group, our method achieved an average F1 value of 99.83% and better results than other state-of-the-art methods. Significance. We proposed a novel heartbeat classification method based on a transformer model. This method provides a new solution for real-time electrocardiogram heartbeat classification, which can be applied to wearable devices
Analytical model for 2DEG charge density in β-(Al
x
Ga1−x
)2O3/Ga2O3 HFET
Authors: Patnaik Akash , Jaiswal Neeraj K , Singh Rohit , Sharma Pankaj
Published: December 2021

In this paper, a physics-based analytical model for two-dimensional electron gas (2DEG) charge density (n
s) and pinch-off voltage (V
off) in

β

-(Al
x
Ga1−x
)2O3/Ga2O3 heterostructure field effect transistor (HFET) is reported. The modeling approach includes solving the Poisson–Schrödinger equation in

β

-(Al
x
Ga1−x
)O3 barrier layer followed by using standard Fermi–Dirac statistics equations for calculating 2DEG charge density in the potential well. The developed model is then used to analyze the effect of Al composition (x) and barrier thickness (d) of

β

-(Al
x
Ga1−x
)2O3 layer on 2DEG charge density. The obtained parameters from our model for charge density and pinch-off voltages are validated with the experimental results in the literature demonstrating a good accuracy. It was observed that the 2DEG charge density increases with Al composition and Al
x
Ga1−x
O barrier layer thickness, but at the cost of increased pinch off voltage. A trade-off between both is necessary to achieve parametric optimization of

β

-(Al
x
Ga1−x
)2O3/Ga2O3 HFET. This model will be useful to study the various parametric constraints for device optimization in terms of 2DEG charge density and pinch off voltage.
A novel piezoelectric-actuated microgripper simultaneously integrated microassembly force, gripping force and jaw-displacement sensors: design, simulation and experimental investigation
Authors: Wang Kan , Wang Dai-Hua , Zhao Jian-Yu , Hou Song
Published: December 2021

For assembling easy-to-deform and easy-to-broken micropart, accurate acquisition of microassembly force and gripping force during microassembly process while ensuring parallel movement of jaws of microgripper is the key to ensure consistency, accuracy and reliability of microassembly without damage. In addition, simultaneously real-time detection of jaw-displacement of microgripper is also a necessary condition for rapid and accurate microassembly. This paper proposes and realizes a principle of a parallelogram compliant mechanism (PCM) based piezoelectric-actuated microgripper, which simultaneously integrates with microassembly force, gripping force and jaw-displacement sensors for the first time and ensures parallel movement of jaws under no-load and gripping micropart. The major structure of proposed microgripper is a monolithic compliant mechanism (MCM) composed of a primary lever compliant mechanism and three-stage PCM in series. Among them, the third-stage PCM is orthogonal to other two PCM in series. MCM transmits the displacement and force from piezoelectric actuator to jaws while transforming microassembly force, gripping force and jaw-displacement into surface strain of single-notch hinges of PCM with three-stage in series. On this basis, simultaneously sensing microassembly force, gripping force and jaw-displacement is realized by monitoring surface strain of single-notch hinges of three-stage PCM. The sensing equations of the microassembly force, gripping force, and jaw-displacement are established, respectively. A microgripper is manufactured, a microgripper system is realized and the integrated sensors are calibrated. The hysteresis characteristics, creep characteristics and time response are tested experimentally. Two examples of microassembly sub-process are simulated and carried out on the constructed microassembly experimental setup. The theoretical and experimental results show that the designed microgripper can simultaneously acquire the microassembly force, gripping force and jaw-displacement with high sensitivity, linearity and resolution in processes of gripping hohlraum and applying microassembly force to hohlraum while ensuring the parallel movement of the gripping jaws when gripping and not gripping micropart.
A high-resolution electric field sensor based on piezoelectric bimorph composite
Authors: Cheng Miaomiao , Wu Jingen , Guan Mengmeng , Mao Qi , Xian Dan , Hu Zhongqiang , Wang Chenying , Wang Zhiguang , Zhou Ziyao , Zhao Libo , Jiang Zhuangde , Liu Ming
Published: December 2021

The rapid development of the internet of things technology has led to great demand for intelligent electric field sensor (EFS). Several working principles have been proposed, however major challenges remain existed for the requirements of EFS with low-cost, large-range, and high-resolution. In this paper, an EFS based on piezoelectric (PE) bending effect using d
31 mode is developed, where a bending strain is induced on the sandwiched bimorph structure of PZT/PDMS/PZT under an applied electric field, and the capacitance value of the PDMS layer reveals detectable variation. We demonstrate an EFS operating at the stress-mediated coupling between PE ceramic and elastic dielectric polymer, which reveals advantages such as simple fabrication process, low-cost and low power consumption. Due to the sandwiched bimorph structure, the strain caused by the electric field can be effectively transferred to improve the resolution of the device. The constitutive equations for the sandwiched bimorph structure are built, and the working principle of the proposed EFS is demonstrated. The EFS exhibits high sensitivity under both AC and DC electric fields, with a resolution of 0.1 V cm−1 in the range of −3 to 3 kV cm−1. The proposed sensor provides an alternative solution for power equipment fault diagnosis, power frequency electric field detection, etc.
The topological counterparts of non-Hermitian SSH models
Authors: Han Y Z , Liu J S , Liu C S
Published: December 2021

Inspired by the relevance between the asymmetric coupling amplitude and the imaginary gauge field, we construct the counterpart of the non-Hermitian SSH model. The idea is the nonzero imaginary magnetic flux vanishing when the boundary condition changes from periodic to open. The zero imaginary magnetic flux of the counterpart leads to the eliminating of the non-Hermitian skin effect and the non-Hermitian Aharonov–Bohm effect which ensures the recovery of the conventional bulk-boundary correspondence from the non-Bloch bulk-boundary correspondence. We explain how some the non-Hermitian models can be transformed to the non-Hermitian SSH models and how the non-reciprocal hopping in the non-Hermitian SSH models can be transformed from one term to the other terms by the similarity transformations. We elaborate why the effective imaginary magnetic flux disappears due to the interplay of the non-reciprocal hoppings in the partner of the non-Hermitian SSH model. As the results, we obtain the topological invariants of the non-Hermitian SSH model in analytical form defined in conventional Brillouin zone. The non-Hermitian SSH model in domain configuration on a chain is discussed with this method. The technique gives an alternative way to study the topological properties of non-Hermitian systems.
Topological pumping in acoustic waveguide arrays with hopping modulation
Authors: Chen Zhaoxian , Chen Zeguo , Li Zhengwei , Liang Bin , Ma Guancong , Lu Yanqing , Cheng Jianchun
Published: December 2021

Thouless pumping is the adiabatic transportation of quantized charge, which is regarded as the dynamic version of the quantum Hall effect. Here we propose the design of an acoustic system to demonstrate the topological pumping characterized by transporting acoustic energy from one side to the opposite. The system is composed of coupled acoustic waveguide arrays with modulated coupling along both cross-sections and the propagating direction. We explore multiple topological phases by introducing rich spatial frequency or enlarged range of the hopping modulation. Such distinct topological phases are evidenced by adiabatic evolution of the edge states, where the acoustic system varies continuously and slowly along the state propagating direction. The robustness behavior of the edge states transport is also verified with numerical simulations to imply their topology origin. Our work provides a route to realize topological phases and utilize the corresponding edge states in waveguide arrays that can lead to versatile acoustic wave manipulation applications.
Quantum homotopy perturbation method for nonlinear dissipative ordinary differential equations
Authors: Xue Cheng , Wu Yu-Chun , Guo Guo-Ping
Published: December 2021

While quantum computing provides an exponential advantage in solving linear differential equations, there are relatively few quantum algorithms for solving nonlinear differential equations. In our work, based on the homotopy perturbation method, we propose a quantum algorithm for solving n-dimensional nonlinear dissipative ordinary differential equations (ODEs). Our algorithm first converts the original nonlinear ODEs into the other nonlinear ODEs which can be embedded into finite-dimensional linear ODEs. Then we solve the embedded linear ODEs with quantum linear ODEs algorithm and obtain a state ϵ-close to the normalized exact solution of the original nonlinear ODEs with success probability Ω(1). The complexity of our algorithm is O(gηT poly(log(nT/ϵ))), where η, g measure the decay of the solution. Our algorithm provides exponential improvement over the best classical algorithms or previous quantum algorithms in n or ϵ.
Quantum communication for sender anonymity based on single-particle with collective detection
Authors: Li Yuancheng , Yu Chaohang , Wang Qingle , Liu Jiangshan
Published: December 2021

Nowadays, identity protection has turned into a fundamental demand for online activities. Currently, the present quantum anonymous communication protocols mostly rely on multi-entanglement. In this paper, we propose an anonymous communication protocol for anonymous sender by using single-particle states. The protocol can be extended to a communication protocol where the sender and receiver are fully anonymous with the message kept secret. In terms of security, our protocol is designed to comply with the technique of collective detection. Compared to the step-by-step detection, collective detection, in which the participants perform detection only once, reduces the complexity of the protocol to some extent. Moreover, we analytically demonstrate the security of the protocol in the face of active attacks. Any active attack employed by an external or internal attacker cannot reveal any useful information about the sender’s identity. Meanwhile, any malicious behavior will be detected by honest participants.
Strain-engineering in AlGaN/GaN HEMTs: impact of silicon nitride passivation layer on electrical performance
Authors: Das Sanghamitra , Dash Tara Prasanna , Jena Devika , Mohapatra Eleena , Maiti Chinmay Kumar
Published: December 2021

In this work, we present a physics-based analysis of two-dimensional electron gas (2DEG) sheet carrier density and other microwave characteristics such as transconductance and cutoff frequency of AlxGa1−xN/GaN high electron mobility transistors (HEMT). An accurate polarization-dependent charge control-based analysis is performed for microwave performance assessment in terms of current, transconductance, gate capacitances, and cutoff frequency of lattice-mismatched AlGaN/GaN HEMTs. The influence of stress on spontaneous and piezoelectric polarization is included in the simulation of an AlGaN/GaN HEMT. We have shown the change in threshold voltage (Vt) due to tensile and compressive strain with different gate lengths. Also, the influence of stress due to the change in nitride thickness is presented. Our simulation results for drain current, transconductance, and current-gain cutoff frequency for various gate length devices are calibrated and verified with experimental data over a wide range of gate and drain applied voltages, which are expected to be useful for microwave circuit design. The predicted transconductance, drain conductance, and operation frequency are quite close to the experimental data. The AlGaN/GaN heterostructure HEMTs with nitride passivation layers show great promise as a candidate in future high speed and high power applications.
Testing the consistency between cosmological data: the impact of spatial curvature and the dark energy EoS
Authors: Gonzalez Javier E. , Benetti Micol , von Marttens Rodrigo , Alcaniz Jailson
Published: December 2021

The results of joint analyses of available cosmological data
have motivated an important debate about a possible detection of a
non-zero spatial curvature. If confirmed, such a result would imply
a change in our present understanding of cosmic evolution with
important theoretical and observational consequences. In this paper
we discuss the legitimacy of carrying out joint analyses with the
currently available data sets and explore their implications for a
non-flat universe and extensions of the standard cosmological model.
We use a robust tension estimator to perform a quantitative analysis
of the physical consistency between the latest data of Cosmic
Microwave Background, type Ia supernovae, Baryonic Acoustic
Oscillations and Cosmic Chronometers. We consider the flat and
non-flat cases of the ΛCDM cosmology and of two dark energy
models with a constant and varying dark energy EoS parameter. The
present study allows us to better understand if possible
inconsistencies between these data sets are significant enough to
make the results of their joint analyses misleading, as well as the
actual dependence of such results with the spatial curvature and
dark energy parameterizations. According to our results, we conclude
that a joint analysis in the context of a non-flat universe
including the CMB data is only possible if the CMB Lens is taken
into account, otherwise, it potentially leads to misleading
conclusions.
Analytical warm dark matter power spectrum on small scales
Authors: Pordeus-da-Silva G. , Batista R.C. , Medeiros L.G.
Published: December 2021

Using the Reduced Relativistic Gas (RRG) model, we analytically determine
the matter power spectrum for Warm Dark Matter (WDM) on small scales,
k > 1 h/Mpc. The RRG is a simplified model for the ideal relativistic
gas, but very accurate in the cosmological context. In another work,
we have shown that, for typical allowed masses for dark matter particles,
m>5 keV, the higher order multipoles, ℓ ≥ 2, in the Einstein-Boltzmann
system of equations are negligible on scales k < 10 h/Mpc.
Hence, we can follow the perturbations of WDM using the ideal fluid
framework, with equation of state and sound speed of perturbations
given by the RRG model. We derive a Mészáros-like equation for WDM
and solve it analytically in radiation, matter and dark energy dominated
eras. Joining these solutions, we get an expression that determines
the value of WDM perturbations as a function of redshift and wavenumber.
Then we construct the matter power spectrum and transfer function
of WDM on small scales and compare it to some results coming from
Lyman-α forest observations. Besides being a clear and pedagogical
analytical development to understand the evolution of WDM perturbations,
our power spectrum results are consistent with the observations considered
and the other determinations of the degree of warmness of dark matter particles.
Blandford-Znajek mechanism in the general stationary axially-symmetric black-hole spacetime
Authors: Konoplya R.A. , Kunz J. , Zhidenko A.
Published: December 2021

We consider the Blandford-Znajek process of electromagnetic extraction of energy from a general axially symmetric asymptotically flat slowly rotating black hole. Using the general parametrization of the black-hole spacetime we construct formulas for the flux of the magnetic field and the rate of energy extraction, which are valid not only for the Kerr spacetime, but also for its arbitrary axially symmetric deformations. We show that in the dominant order these quantities depend only on a single deformation parameter, which relates the spin frequency of a black hole with its rotation parameter.
High-confinement radiative L-modes in ASDEX Upgrade
Authors: Fable E. , Kallenbach A. , McDermott R.M. , Bernert M. , Angioni C. , the ASDEX Upgrade Team
Published: December 2021

Experiments have been performed in the ASDEX Upgrade tokamak where plasmas are kept just below the H-mode threshold using feedback on the radiated power via seeded impurity. The resulting high-power L-modes show high confinement properties and no ELM activity due to the reduced pedestal height. The physics of these high-confinement L-modes is explored by means of integrated modeling to clarify the origin of the improved confinement.