bluuebunny/crossref_metadata_2025 huggingface dataset:
Event‐triggered load frequency control of smart grids under deception attacks
Authors: Liu Xinghua , Bai Dandan , Wu Yi‐De , Ge Ming‐Feng , Vargas Alessandro N.
Published: March 2021

This paper shows a result for the load frequency control with event‐triggering mechanism under deception attacks. Specifically, the event‐triggering mechanism and deception attacks are considered in the dynamic model of power systems. The event‐triggering is used to reduce the frequency of controller update and communication between nodes. The controller is designed and the stability of the system is guaranteed by utilising the Lyapunov–Krasovskii functional method and truncated Bessel–Legendre inequality. Finally, a three‐area interconnected networked power system is given and the simulated results are presented to show the effectiveness of the developed theoretical results.
Low‐complexity joint active and passive beamforming for RIS‐aided MIMO systems
Authors: Siddiqi Muhammad Zain , Mir Talha , Hao Mo , MacKenzie Richard
Published: March 2021

In this paper, we consider the reconfigurable intelligent surface (RIS)‐aided MIMO systems to realize a high quality link between the base station (BS) and the users via a RIS. To achieve this goal, the active beamforming at the BS and the passive beamforming at the RIS should be jointly optimized. However, most of the existing joint optimization schemes that maximize the sum‐rate have high computational complexity due to the complex derivative calculations and matrix inversion. To this end, a biologically inspired particle swarm optimization (PSO) algorithm is exploited to solve the non‐convex sum‐rate optimization problem with low‐complexity. Simulation results show that the proposed scheme provides a better trade‐off between performance and complexity than existing solutions for RIS‐aided MIMO systems.
A review of approaches investigated for right ventricular segmentation using short‐axis cardiac MRI
Authors: Ammari Asma , Mahmoudi Ramzi , Hmida Badii , Saouli Rachida , Bedoui Mohamed Hédi
Published: March 2021

The right ventricular assessment is crucial to heart disease diagnosis. Unfortunately, its segmentation is quite challenging due to its intricate shape, ill‐defined thin edges, large variability among patients, and pathologies. Besides, it is a very laborious and time‐consuming task to be done manually. Therefore, automated segmentation techniques are very suitable to reduce the strain on the expert. Here, it is attempted to review the taxonomy of the current RV segmentation approaches adopted to handle the afore‐mentioned issues. Enhanced by our expert's interpretation, the results of over forty research papers were evaluated based on several metrics such as the dice metric and the Hausdorff distance. Synthetic tables and charts were also used to discuss the reviewed approaches. The following study shows that none of the existing methods has proved accurate enough to meet all the RV challenging issues. Many misestimated results were reported for several cases. Eventually, global guidance is outlined, which supports combining different methods to enhance the expected results during the MRI short‐axis slice processing.
DuGAN: An effective framework for underwater image enhancement
Authors: Zhang Huiqing , Sun Luyu , Wu Lifang , Gu Ke
Published: March 2021

Underwater image enhancement is an important low‐level vision task with much attention of community. Clear underwater images are helpful for underwater operations. However, raw underwater images often suffer from different types of distortions caused by the underwater environment. To solve these problems, this paper proposes an end‐to‐end dual generative adversarial network (DuGAN) for underwater image enhancement. The images processed by existing methods are taken as training samples for reference, and they are segmented into clear parts and unclear parts. Two discriminators are used to complete adversarial training toward different areas of images with different training strategies, respectively. The proposed method is able to output more pleasing images than reference images benefit by this framework. Meanwhile, to ensure the authenticity of the enhanced images, content loss, adversarial loss, and style loss are combined as loss function of our framework. This framework is easy to use, and the subjective and objective experiments show that excellent results are achieved compared to those methods mentioned in the literature.
Bike‐sharing systems with a dual selection mechanism and a dynamic double‐threshold repositioning policy
Authors: Fan Rui‐Na , Ma Fan‐Qi
Published: March 2021

Bike‐sharing systems have gained considerable attention with the tide of sharing economy. This paper proposes a dual selection mechanism and a dynamic double‐threshold repositioning policy to reduce problematic stations. The selection mechanism is a preventive self‐balancing measure, which is carried out before problematic stations appear. To prove the effectiveness of this selection mechanism, a system of differential equations is set up, the steady‐state probabilities of the bike‐sharing system are computed, and numerical experiments to verify the applicability and computability of the computational method are provided. The method providd in this study contributes to improving the efficiency of the bike‐sharing by self‐balancing measure.
Inclusive tourism as a method for rehabilitation and restoration of human well-being
Authors: Churilina Irina , Larchenko Lyubov , Anisimov Timur , Volkov Alexey
Published: March 2021

The aim of the research is to study the impact of inclusive tourism on the subjective assessment of the well-being level of tourists with disabilities and tourists without disabilities. The article deals with the issues of the conceptual apparatus of inclusive tourism, the peculiarities of its organization in Russia, taking into account foreign experience. Moreover, the study highlights the issues of inclusive tourism that have an impact on human well-being. Based on a sociological survey, the attitude to inclusive tourism as a way of influencing the subjective feeling of well-being in people with disabilities and in people without functional impairments is analyzed. The results of the study show that people with disabilities not only visit exhibitions and theaters, but also travel around Russia and other countries. It is concluded that there are positive shifts of respondents towards the implementation of the idea of inclusive tourism, since there is a direct relationship between the number of travels and the well-being of respondents. It is emphasized that a wide questionnaire survey, discussion of inclusive tours is already influencing the formation of a new level of consciousness of all participants in the tourism market and even at this stage creates new opportunities for the formation of human well-being.
Search for Available Biomechanical Technologies Suitable for Use in Physical Education Classes
Authors: Pomerantsev Andrey
Published: March 2021

Introduction: One of the most important physical education tasks in school is to learn motor actions. Biomechanical technologies can promote to this process. A school lesson is different from a sports training, so it is necessary keep in mind its specifics. The purpose of the article is to analyse the existing professional biomechanical complexes for their suitability for use in physical education classes. Methods: We studied articles on sports biomechanics and selected 20 professional biomechanical complexes. These complexes can be divided into four technological groups: Optoelectronic Measurement Systems (OMSs), Electromagnetic Measurement Systems (EMSs), Image Processing Systems (IMSs), Inertial Sensory Systems (IMUs). Besides that, we identified 10 crucial categories to estimate opportunity to use biomechanical complexes in school lessons: cost, complexity of setting up and using, assistance need, portability, universality, room volume, construction traumatic, place for using, promptness, volume of data. Thus, each complex was evaluated according to 10 criteria. The biomechanical complex was excluded from further consideration if it got a critical limitation at least one of the criteria. Results: None of the professional biomechanical complexes can be considered suitable for use in physical education classes. As alternative we propose using free biomechanical software and smartphone camera with slow-motion caption.
Educational Program “Healthy Lifestyle University” for Medical Students’ Vocational Adjustment Development
Authors: Potapchuk Alla Askoldovna , Vanchakova Nina Pavlovna , Vorontsova Elizaveta Valerjevna , Shaporov Anton Mikhailovitch , Bogatyrev Andrei Anatoljevich
Published: March 2021

The paper describes the design and the essential results of a specially developed educational program “Healthy Lifestyle University”. This program can be viewed as an effective tool of medical students’ lifestyle monitoring as well as social and vocational position development. The program has been designed and implemented in Pavlov First Saint Petersburg State Medical University, and successfully tested in the XI open public All-Russian competition of educational institutions of higher education (subordinate to the Ministry of HealthCare of the Russian Federation). The program was the winner in the category “Higher Education Institution of Healthy Lifestyle”. The essential educational components of the program, dedicated to dissemination of medical knowledges and fostering healthy lifestyle in medical students are disclosed in the article. The results of the survey reflect modern medical students’ modus vivendi and the concept of “healthy lifestyle” perceptions, as well as students’ troubles, needs and suggestions for further improvement of healthy lifestyle conditions, facilities and opportunities. These provide essential guidelines for further development of healthy and student-friendly university environment in Russia. The propagated healthy lifestyle set of values and attitudes contributes to vocational adjustment and vocational position formation, as well as personal and vocational selfreflection preparedness development of medical students.
On a nonlinear Schrödinger equation for nucleons in one space dimension
Authors: Klein Christian , Rota Nodari Simona
Published: March 2021

We study a 1D nonlinear Schrödinger equation appearing in the description of a particle inside an atomic nucleus. For various nonlinearities, the ground states are discussed and given in explicit form. Their stability is studied numerically via the time evolution of perturbed ground states. In the time evolution of general localized initial data, they are shown to appear in the long time behaviour of certain cases.
Study of the influence of dithizone as an eco-friendly corrosion inhibitor on the corrosion behaviour of AA7075 aluminium alloy in neutral chloride solution
Authors: Acila Meryem , Bensabra Hakim , Santamaria Monica
Published: March 2021

The effect of 1,5-diphenylthiocarbazone (dithizone) as an eco-friendly corrosion inhibitor for protection of AA7075 aluminium alloy in chloride containing aggressive environment was studied by means of weight-loss, electrochemical measurements and Raman spectroscopy. The results indicate that the addition of dithizone decreases significantly the corrosion rate of AA7075 alloy, with efficiency proportional to the inhibitor concentration. The polarization curves show that dithizone works as mixed-type inhibitor to slow down the anodic and cathodic reaction kinetic. The morphology revealed by scanning electron microscopy and the Raman spectroscopy analysis clearly shows that the inhibitor contributes in the formation of a stable protective film on the AA7075 alloy due to the adsorption of dithizone molecules on aluminium alloy surface obeying Langmuir adsorption isotherm.
Citizen social science in practice: the case of the Empty Houses Project
Authors: Albert Alexandra
Published: March 2021

The growth of citizen science and participatory science, where non-professional scientists voluntarily participate in scientific activities, raises questions around the ownership and interpretation of data, issues of data quality and reliability, and new kinds of data literacy. Citizen social science (CSS), as an approach that bridges these fields, calls into question the way in which research is undertaken, as well as who can collect data, what data can be collected, and what such data can be used for. This article outlines a case study—the Empty Houses Project—to explore how CSS plays out in practice, and to reflect on the opportunities and challenges it presents. The Empty Houses Project was set up to investigate how citizens could be mobilised to collect data about empty houses in their local area, so as to potentially contribute towards tackling a pressing policy issue. The study shows how the possibilities of CSS exceed the dominant view of it as a new means of creating data repositories. Rather, it considers how the data produced in CSS is an epistemology, and a politics, not just a realist tool for analysis.
Spectral properties of the singular Friedrichs–Lee Hamiltonian
Authors: Facchi Paolo , Ligabò Marilena , Lonigro Davide
Published: March 2021

We show that the Friedrichs–Lee model, which describes the one-excitation sector of a two-level atom interacting with a structured boson field, can be generalized to singular atom–field couplings. We provide a characterization of its spectrum and resonances and discuss the inverse spectral problem.
Crystallographic analysis of nano-tendril bundle vs fuzz growth on tungsten exposed to helicon wave-coupled helium plasma
Authors: Woller K. B. , Whyte D. G. , Wright G. M.
Published: March 2021

The propensity for nano-tendril bundle (NTB) vs widespread nano-tendril growth (i.e., fuzz) on polycrystalline W under varying ion energy modulation conditions, from DC to peak-to-peak energy modulation of 42 eV at 13.56 MHz, is correlated with the crystal orientation of the underlying grains. Grains that are vicinal to crystal orientations with high surface diffusivity (e.g., {101} for a body centered cubic crystal structure) exhibit NTB growth at lower ion energy modulation amplitude than grains that are vicinal to low surface diffusivity orientations, such as {100}. Adatom mobility considerations are presented to describe the experimental observations. These results support that surface diffusion or W adatom mobility enhanced by ion bombardment plays a key role in the surface morphology evolution of W under He irradiation.
Numerical solution of two-dimensional fractional order Volterra integro-differential equations
Authors: Ahsan Sumbal , Nawaz Rashid , Akbar Muhammad , Nisar Kottakkaran Sooppy , Abualnaja Kholod M. , Mahmoud Emad E. , Abdel-Aty Abdel-Haleem
Published: March 2021

The present paper is concerned with the implementation of the optimal homotopy asymptotic method to find the approximate solutions of two-dimensional fractional order Volterra integro-differential equations. The technique’s applicability and validity are tested through some numerical examples. The fractional order derivatives are calculated using Caputo’s sense. Results obtained by the proposed technique are compared with the Legendre wavelet method. The proposed method provides us with efficient and more accurate solutions than the other existing methods in the literature. Error analysis and convergence of the proposed method are also provided in the paper.
Spin-orbit torque and Dzyaloshinskii–Moriya interaction in 4d metal Rh-based magnetic heterostructures
Authors: Cao Cuimei , Chen Shiwei , Song Wenjie , Zhu Xiaoyan , Hu Shuai , Qiu Xuepeng , Chai Guozhi , Sun Lin , Cheng Wenjuan , Jiang Dongmei , Zhan Qingfeng
Published: March 2021

The electrical switching of magnetization through spin–orbit torque (SOT) has potential applications for energy-efficient spintronic devices. Previous studies focused mostly on 5d heavy metals with strong spin–orbit coupling (SOC) to generate a spin current or a nonequilibrium spin accumulation and exert SOTs on the magnetization of a neighboring ferromagnetic layer. Recent theoretical and experimental studies indicated that 4d metals with weak SOC may also generate a sizable torque and realize the current-induced magnetization switching. In this work, we studied the current-induced SOTs in 4d metal Rh-based magnetic heterostructures with a perpendicular magnetic anisotropy. The damping-like SOT efficiency ξDL of [Ni/Co]3/Rh multilayers increases with the Rh thickness tRh and becomes saturated at tRh = 5 nm. Although the spin-Hall angle of Rh is rather small about 0.028 ± 0.005, a reversible current-induced SOT switching can still be achieved. In addition, the interfacial Dzyaloshinskii-Moriya interaction (iDMI) in Rh/Co heterostructures was quantitatively characterized by using Brillouin light scattering. The iDMI constant D increases with tRh and reaches 224 ± 39 μJ/m2 at tRh = 5 nm. Our results indicated that even for a weak SOC 4d metal Rh, it is still possible to obtain a current-induced magnetization switching and observe an obvious iDMI effect in the Rh-based magnetic heterostructures, which may broaden the scope of spintronic materials used for SOT devices.
Continuous adjoint complement to the Blasius equation
Authors: Kühl Niklas , Müller Peter Marvin , Rung Thomas
Published: March 2021

This manuscript is concerned with a continuous adjoint complement to two-dimensional, incompressible, first-order boundary-layer equations for a flat plate boundary layer. The text is structured into three parts. The first part demonstrates that the adjoint complement can be derived in two ways, following either a first simplify then derive or a first derive and then simplify strategy. The simplification step comprises the classical boundary-layer (BL) approximation, and the derivation step transfers the primal flow equation into a companion adjoint equation. The second part of the paper comprises the analyses of the coupled primal/adjoint BL framework. This leads to similarity parameters, which turn the partial-differential-equation (PDE) problem into a boundary value problem described by a set of ordinary-differential-equations (ODEs) and support the formulation of an adjoint complement to the classical Blasius equation. Opposite to the primal Blasius equation, its adjoint complement consists of two ODEs, which can be simplified depending on the treatment of advection. It is shown that the advective fluxes, which are frequently debated in the literature, vanish for the investigated self-similar BL flows. Differences between the primal and the adjoint Blasius framework are discussed against numerical solutions, and analytical expressions are derived for the adjoint BL thickness, wall shear stress, and subordinated skin friction and drag coefficients. The analysis also provides an analytical expression for the shape sensitivity to shear driven drag objectives. The third part assesses the predictive agreement between the different Blasius solutions and numerical results for Navier–Stokes simulations of a flat plate BL at Reynolds numbers between 103≤ReL≤105. It is seen that the reversal of the inlet and outlet locations and the direction of the flow, inherent to the adjoint formulation of convective kinematics, poses a challenge when investigating real finite length (finite Re-number) flat plate boundary layer problems. Efforts to bypass related issues are discussed.
Peltier effects in lithium-ion battery modeling
Authors: Spitthoff Lena , Gunnarshaug Astrid Fagertun , Bedeaux Dick , Burheim Odne , Kjelstrup Signe
Published: March 2021

A high battery temperature has been shown to be critical for lithium-ion batteries in terms of performance, degradation, and safety. Therefore, a precise knowledge of heat sources and sinks in the battery is essential. We have developed a thermal model for lithium-ion batteries, a model that includes terms not included before, namely, Peltier and Dufour heat effects. The model is derived using non-equilibrium thermodynamics for heterogeneous systems, the only theory which is able to describe in a systematic manner the coupling of heat, mass, and charge transport. The idea of this theory is to deal with surfaces as two-dimensional layers. All electrochemical processes in these layers are defined using excess variables, implying, for instance, that the surface has its own temperature. We show how the Peltier and Dufour heats affect a single cell and may produce an internal temperature rise of 8.5 K in a battery stack with 80 modules. The heat fluxes leaving the cell are also functions of these reversible heat effects. Most of the energy that is dissipated as heat occurs in the electrode surfaces and the electrolyte-filled separator. The analysis shows that better knowledge of experimental data on surface resistances, transport coefficients, and Dufour and Peltier heats is essential for further progress in thermal modeling of this important class of systems.
Wall shear stress distribution in a compliant airway tree
Authors: Stéphano Jonathan , Mauroy Benjamin
Published: March 2021

The airflow in the bronchi applies a shear stress on the bronchial mucus, which can move the mucus. The air–mucus interaction plays an important role in cough and in chest physiotherapy (CP). The conditions under which it induces a displacement of the mucus are still unclear. Yet, the air–mucus interaction justifies common technics of CP used to help the draining of the mucus in prevalent diseases. Hence, the determination of the distribution of the shear stress in the lung is crucial for understanding the effects of these therapies and, potentially, improves their efficiency. We develop a mathematical model to study the distribution of the wall shear stress (WSS) induced by an air flow exiting an airway tree. This model accounts for the main physical processes that determine the WSS, more particularly the compliance of the airways, the air inertia, and the tree structure. We show that the WSS distribution in the tree depends on the dynamics of the airways deformation and on the air inertia. The WSS distribution in the tree exhibits a maximum whose amplitude and location depend on the amount of air flow and on the “tissue” pressure surrounding the airways. To characterize the behavior of the WSS at the tree bifurcations, we derive new analytical criteria related to the airway size reduction in the bifurcations. Our results suggest that a tuning of the airflow and of the tissue pressure during a CP maneuver might allow to control, at least partially, the air–mucus interaction in the lung.
Plasma parameter profile inference from limited data utilizing second-order derivative priors and physic-based constraints
Authors: Nishizawa T. , Cavedon M. , Dux R. , Reimold F. , Toussaint U. von ,   ASDEX Upgrade Team
Published: March 2021

A Bayesian framework has been used to improve the quality of inferred plasma parameter profiles. An integrated data analysis allows for coherent combinations of different diagnostics, and Gaussian process regression provides a reliable regularization process and systematic uncertainty estimation. In this paper, we propose a new profile inference framework that utilizes our prior knowledge about plasma physics, along with integrated data analysis and a Gaussian process. In order to facilitate the use of the Markov chain Monte Carlo sampling, we use a Gaussian process to define quantities corresponding to the second derivatives of the profiles. We validate the analysis technique by using a synthetic one-dimensional plasma, in which the transport properties are known and demonstrate that the proposed analysis technique can infer plasma parameter profiles from line-integrated measurements only. Furthermore, we can even infer unknown parameters in our physics models when our physics knowledge on the system is incomplete. This analysis framework is applicable to laboratory plasmas and provides a means to investigate plasma parameters, to which standard diagnostics are not directly sensitive.
The efficient calculation of electron impact ionization cross sections with effective core potentials
Authors: Graves Vincent , Cooper Bridgette , Tennyson Jonathan
Published: March 2021

A black box Binary Encounter Bethe (BEB) with an effective core potential (ECP) procedure is implemented, which facilitates the efficient calculation of electron impact ionization cross sections for molecules that include heavy atoms. This is available in the Quantemol electron collisions software, a user friendly graphical user interface to the UKRMol+ codes. Tests were performed for the following series of molecules: CF4, CCl4, CBr4, CI4, and CAt4; CH4, SiH4, GeH4, and SnH4; PH3, PF3, and PCl3; SiCl4 and BCl3; and CH3Br and CF3I. Use of an ECP generally raises the predicted ionization cross section at lower energies leading to improved agreement with experiment compared to all electron calculations for BEB cross sections. Scaling BEB cross sections by the polarizability of the target molecule is shown to give somewhat erratic results, which do not always provide closer agreement with the measured cross sections.
Sensitivity of sum frequency generation experimental conditions to thin film interference effects
Authors: Cotton Daniel E. , Roberts Sean T.
Published: March 2021

Sum-frequency generation (SFG) spectroscopy has furthered our understanding of the chemical interfaces that guide key processes in biology, catalysis, environmental science, and energy conversion. However, interpreting SFG spectra of systems containing several internal interfaces, such as thin film electronics, electrochemical cells, and biofilms, is challenging as different interfaces within these structures can produce interfering SFG signals. One potential way to address this issue is to carefully select experimental conditions that amplify the SFG signal of an interface of interest over all others. In this report, we investigate a model two-interface system to assess our ability to isolate the SFG signal from each interface. For SFG experiments performed in a reflective geometry, we find that there are few experimental conditions under which the SFG signal originating from either interface can be amplified and isolated from the other. However, by performing several measurements under conditions that alter their interference, we find that we can reconstruct each signal even in cases where the SFG signal from one interface is more than an order of magnitude smaller than its counterpart. The number of spectra needed for this reconstruction varies depending on the signal-to-noise level of the SFG dataset and the degree to which different experiments in a dataset vary in their sensitivity to each interface. Taken together, our work provides general guidelines for designing experimental protocols that can isolate SFG signals stemming from a particular region of interest within complex samples.
Predicting efficiencies >25% A3MX3 photovoltaic materials and Cu ion implantation modification
Authors: Feng Hong-Jian , Zhang Qiang
Published: March 2021

Halide perovskite exhibits remarkable photovoltaic (PV) performance so far, however, its toxicity and instability hinder the commercialization. Researchers are devoted to explore nontoxic and stable solar cell alternatives with high efficiency. Considering the octahedra network and the high symmetry crystalline structure of prototype Mg3NF3 (Pm-3m), which is similar to the halide perovskites and tends to create high p-s band edge states transition probability associated closely with the excellent PV performance. We extensively screened the potential PV materials from 64 compounds in A3MX3 (A = Mg, Ca, Sr, Ba; M = N, P, As, Sb; X = F, Cl, Br, I) structure based on the bandgap, theoretical efficiency, band edge states transition, and thermal stability. Three Pb-free compounds, i.e., Ba3PI3, Ba3AsI3, and Ba3SbI3, are found to be ideal stable PV materials with the efficiency (25.9%) comparable to that of halide perovskites. The optical absorption of the best PV candidate, i.e., Ba3SbI3, has been improved further by low energy Cu ion implantation, and the occurrence of the threshold velocity in the electronic stopping power and the derived bandgap confirm again the high accuracy of our density functional theory results.
Investigation of heat transport using directly driven gold spheres
Authors: Farmer W. A. , Rosen M. D. , Swadling G. F. , Bruulsema C. , Harris C. D. , Rozmus W. , Schneider M. B. , Sherlock M. W. , Edgell D. H. , Katz J. , Ross J. S.
Published: March 2021

Recently, heat transport was investigated using a directly driven beryllium sphere [Farmer et al., Phys. Plasmas 27, 082701 (2020)]. Models that overly restrict heat transport were rejected. This paper extends work to directly driven gold spheres where radiation loss is more important. Here, gold coated spheres are directly driven at the OMEGA laser facility at intensities of 5×1014 W/cm2. Plasma conditions, laser coupling, and x-ray flux are all measured. Comparisons to 2D radiation-hydrodynamic simulations are performed. Simulations use three common heat transport models: local transport with flux limiters of f = 0.15 and f = 0.03, and the nonlocal Schurtz–Nicolai–Busquet (SNB) model. It is shown that both the SNB model and f = 0.15 match the measured plasma conditions with the SNB model better capturing the temporal evolution of electron temperature. The f = 0.03 model predicts too low of an electron density and too hot of a temperature. The measured scattered light is roughly 6% of the incident energy, the f = 0.15 and SNB models predict 0.5% uncoupled light, and f = 0.03, 38% uncoupled light. The x-ray fluxes in the f = 0.15 and SNB simulations rise too quickly and are just outside the measurement's error, while the x-ray flux in the f = 0.03 simulation is low by a factor of two-three. For these reasons, the f = 0.03 model is rejected.
Large thermal hysteresis of ferroelectric transition in HfO2-based ferroelectric films
Authors: Mimura Takanori , Shimizu Takao , Sakata Osami , Funakubo Hiroshi
Published: March 2021

The transition between the dielectric tetragonal and ferroelectric orthorhombic phases in 7%Y doped HfO2 and Hf0.5Zr0.5O2 films with various orientations and film thicknesses was investigated by high-temperature x-ray diffraction. All films demonstrate a different phase transition temperature on heating and cooling with thermal hysteresis with a gap of ΔT. This result clearly shows that the phase transition of the ferroelectric HfO2-based film is first order. The ΔT value of 40–210 °C in HfO2-based films is larger than that of other ferroelectric materials but similar to that of martensitic materials with large lattice deformation. This implies that the ferroelectric phase transition of HfO2-based films involves large lattice deformation. Moreover, we show that ΔT is changed by the size and composition effects. Our results are a step toward elucidating the mechanism of phase transition in ferroelectric HfO2-based films.
Inversion of angular-dependent planar magnetoresistance in epitaxial Pt/γ′-Fe4N bilayers
Authors: Shi Xiaohui , Jin Chao , Mi Wenbo
Published: March 2021

The conversion between charge and spin through spin–orbit coupling (SOC) is critical in heavy nonmagnetic metal/ferromagnetic metal systems. Here, both the single γ′-Fe4N films and the epitaxial Pt/γ′-Fe4N bilayers were fabricated by facing-target sputtering. In the Pt(3 nm)/γ′-Fe4N(tFe4N ≤ 6 nm) bilayers, the anisotropy magnetoresistance (AMR) exhibits an “M” shape, which is opposite to that of the single γ′-Fe4N film with a “W” shape. Meanwhile, the planar Hall resistivity (PHR) reversal also appears. The inversion of AMR and PHR after capping a 3-nm-thick Pt layer on the γ′-Fe4N layer is mainly determined by the interfacial effect, in which the magnetic-proximity-effect induced the interface Pt local moments and the inverse-spin-Hall-effect caused the reflected spin-current to charge-current conversion. Our work helps to understand the interfacial SOC effects and has potential application in the field of magnetic sensors.
Prototype equation of state for phase transition of confined fluids based on the generalized van der Waals partition function
Authors: Adidharma Hertanto , Tan Sugata P.
Published: March 2021

A simple self-consistent prototype equation of state (EOS) based on the generalized van der Waals (vdW) partition function has been demonstrated to describe the phase transition of simple fluids in nanopores with uniform size. Different from those commonly presented in the literature, the new EOS does not need an auxiliary equation that is conventionally applied to provide the capillary pressure derived from surface tension. The encouraging performance of the EOS calls for further extension to applications with more complex fluids and porous media.
Origin of vibrational features in the excitation energy transfer dynamics of perylene bisimide J-aggregates
Authors: Kundu Sohang , Makri Nancy
Published: March 2021

We investigate the role of intramolecular normal mode vibrations in the excitation energy transfer (EET) dynamics of perylene bisimide J-aggregates composed of 2 or 25 units using numerically exact methods. The calculations employ a Frenkel exciton Hamiltonian where the ground and excited electronic states of each molecular unit are coupled to 28 intramolecular normal mode vibrations at various temperatures. The electronic populations exhibit strong damping effects, a lengthening of the EET time scale, and complex dynamical patterns, which depend on aggregate length, temperature, as well as electronic and vibrational initial conditions and which are not additive. The early evolution is dominated by high-frequency vibrational modes, but all modes are responsible for the observed dynamics after the initial 25 fs. Overall, we observe significant changes in the electronic populations upon varying the temperature between 0 and 600 K. With a Franck–Condon (FC) initial excitation, a strongly coupled vibrational mode introduces new peaks to the dimer populations, which show very weak temperature sensitivity. The first of these peaks is also seen in the long aggregate, but subsequent recurrences appear strongly quenched and merged. These structures are drastically altered if a non-FC initial condition is assumed. Additional insights are obtained from the diagonal elements of the dimer electronic-vibrational reduced density matrix. We find that the vibronic peaks result from depletion of the crossing region during the early coherent evolution of the vibrational density away from the crossing point, which allows the premature back-transfer of excitation to the initially excited unit.
Influence of the piezoelectric material on the signal and noise of magnetoelectric magnetic field sensors based on the delta-E effect
Authors: Spetzler Benjamin , Su Jingxiang , Friedrich Ron-Marco , Niekiel Florian , Fichtner Simon , Lofink Fabian , Faupel Franz
Published: March 2021

Magnetoelectric thin-film sensors based on the delta-E effect have widely been reported for the detection of low frequency and small amplitude magnetic fields. Such sensors are usually fabricated with microelectromechanical system technology, where aluminum nitride (AlN) is the established piezoelectric material. Here, we present aluminum scandium nitride (AlScN) for delta-E effect sensors instead and compare it with AlN using two sensors of identical design. The sensors are experimentally and theoretically analyzed regarding sensitivity, noise, limit of detection (LOD), and resonator linearity. We identify the influence of the dominating piezoelectric coefficients dij and other material parameters. Simulations and measurements demonstrate that, in contrast to the conventional direct operation of magnetoelectric sensors, a sensitivity increase ∝dij2 and a LOD improvement ∝dij−1 can be achieved if thermal–mechanical noise is dominant. In the present case, an 8× improved sensitivity and LOD are measured with AlScN at small excitation amplitudes. This factor decreases with increasing amplitude and resonator nonlinearities. The overall minimum LOD does not change due to an earlier onset of magnetic noise in the AlScN sensor. All in all, this study reveals the influence of the piezoelectric material on the signal and noise of delta-E effect sensors and the potential of AlScN to significantly improve sensitivity.
Transitional pulsatile flows with stenosis in a two-dimensional channel
Authors: Ding Guanghui , Choi Kwing-So , Ma Binghe , Kato Tomonori , Yuan Weizheng
Published: March 2021

Although blood flows are mostly laminar, transition to turbulence and flow separations are observed at curved vessels, bifurcations, or constrictions. It is known that wall-shear stress plays an important role in the development of atherosclerosis as well as in arteriovenous grafts. In order to help understand the behavior of flow separation and transition to turbulence in post-stenotic blood flows, an experimental study of transitional pulsatile flow with stenosis was carried out using time-resolved particle image velocimetry and a microelectromechanical systems wall-shear stress sensor at the mean Reynolds number of 1750 with the Womersley number of 6.15. At the start of the pulsatile cycle, a strong shear layer develops from the tip of the stenosis, increasing the flow separation region. The flow at the throat of the stenosis is always laminar due to acceleration, which quickly becomes turbulent through a shear-layer instability under a strong adverse pressure gradient. At the same time, a recirculation region appears over the wall opposite to the stenosis, moving downstream in sync with the movement of the reattachment point. These flow behaviors observed in a two-dimensional channel flow are very similar to the results obtained previously in a pipe flow. We also found that the behavior in a pulsating channel flow during the acceleration phase of both 25% and 50% stenosis cases is similar to that of the steady flow, including the location and size of post-stenotic flow separation regions. This is because the peak Reynolds number of the pulsatile flow is similar to that of the steady flow that is investigated. The transition to turbulence is more dominant for the 50% stenosis as compared to the 25% stenosis, as the wavelet spectra show a greater broadening of turbulence energy. With an increase in stenosis to 75%, the accelerating flow is directed toward the opposite wall, creating a wall jet. The shear layer from the stenosis bifurcates as a result of this, one moving with the flow separation region toward the upper wall and the other with the wall jet toward the bottom wall. Low wall-shear stress fluctuations are found at two post-stenotic locations in the channel flow – one immediately downstream of the stenosis over the top wall (stenosis side) inside the flow separation region, and the other in the recirculation region on the bottom wall (opposite side of the stenosis).
Hartree–Fock critical nuclear charge in two-electron atoms
Authors: Burton Hugh G. A.
Published: March 2021

Electron correlation effects play a key role in stabilizing two-electron atoms near the critical nuclear charge, representing the smallest charge required to bind two electrons. However, deciphering the importance of these effects relies on fully understanding the uncorrelated Hartree–Fock description. We investigate the properties of the ground state wave function in the small nuclear charge limit using various symmetry-restricted Hartree–Fock formalisms. We identify the nuclear charge where spin-symmetry breaking occurs to give an unrestricted wave function that predicts an inner and outer electron. We also identify closed-shell and unrestricted critical nuclear charges where the highest occupied orbital energy becomes zero and the electron density detaches from the nucleus. Finally, we identify the importance of fractional spin errors and static correlation for small nuclear charges.
Effect of nonmagnetic substituent Zn on the phase competition and multiferroic properties in the polar magnet Fe2Mo3O8
Authors: Wang W. , Li P. Z. , Chang Y. T. , Liu M. F. , Lu C. L. , Lu X. B. , Zeng M. , Liu J.-M.
Published: March 2021

The polar magnet, Fe2Mo3O8 (FMO), with linear magnetoelectric (ME) coupling, is a promising candidate for multiferroic applications in advanced spin devices. However, a giant magnetic bias (Hb) is needed for optimizing the inverse ME effect, i.e., electric field (E) modulation of magnetization (M), which is still a core issue. Herein, we utilize the chemical doping route to enhance the sensitivity of controlling the competitive magnetic interactions and/or multiferroic phases by means of introducing nonmagnetic Zn2+ ions into FMO crystals. Compared with FMO, the Zn-doped composition (Fe0.95Zn0.05)2Mo3O8 (FZMO) generates three metastable magnetic states in the middle of antiferromagnetic and ferrimagnetic states, along with obvious ferroelectric polarization. The inverse ME effect of FZMO is intact with a relative change of ΔM ≈ 0.06 μB/f.u. responding to an E value of ± 20 kV/cm at 52 K. Most interestingly, the exciting Hb is dramatically dropped to 0.8 T for FZMO from 5.1 T for FMO, which is in favor of the application of ME coupling. It is suggested that the perturbation of magnetic interactions via substituting specific sites by nonmagnetic ions plays a key role in decreasing the exciting Hb without deteriorating the inverse ME coupling in this polar M2Mo3O8 family.
Covalent functionalization in graphene nanoribbon: Theoretical modeling and sensitivity analysis
Authors: Thriveni G. , Ghosh Kaustab
Published: March 2021

The alteration of electronic properties in chemically modified graphene can be utilized for chemical and biosensing applications. Thus, it is essential to understand how the alteration of density of states and conductance spectra of functionalized zigzag and armchair graphene nanoribbon (GNR) affects its sensitivity. In this aspect, the current–voltage characteristics of GNR based sensors are modeled using the non-equilibrium Green's function method. Our findings show that the presence of chemical moiety at one edge of the zigzag GNR structure opens the bandgap that reduces the current conduction and enhances the sensitivity for detection. However, double edge functionalization restores the semi-metallic character of the zigzag ribbon that reduces the sensitivity. Both single and double edge atomic substitution in armchair ribbon makes it n-type, which shows the alteration in current conduction for detecting the presence of the chemical species. We further found that increasing the width of the ribbon decreases the device sensitivity while it increases for the double edge substituted zigzag structure. The study thus provides essential information and insights into utilizing and operating different edge structures of graphene based sensors for effective detection of chemical and biomolecular species.
Tunable asymmetric acoustic transmission via binary metasurface and zero-index metamaterials
Authors: Gu Zhongming , Fang Xinsheng , Liu Tuo , Gao He , Liang Shanjun , Li Yong , Liang Bin , Cheng Jianchun , Zhu Jie
Published: March 2021

The pursuit of tunable asymmetric sound transmission has been a long-term topic since it could contribute to providing more flexibilities in many areas of acoustic engineering. The interference effect can be a feasible approach in which two waves with the same frequency superposed to form the resultant wave with manipulated amplitude according to the relative phase difference between them. However, strictly speaking, restricted by the spatial variance of phase, the manipulated domain created by the specific phase difference is always limited to a spot with dimensions much smaller than the wavelength. Here, we proposed a design to break this barrier that can realize the tunable asymmetric transmission via the combination of zero-index metamaterials and the binary metasurface. The zero-index metamaterial can provide the effective extremely large speed to shrink the infinite domain into a spot acoustically and the binary metasurface can be used to tune the specific phase difference. Numerical simulations and experimental measurements have good agreement and show that the acoustic waves impinged from the side of metasurface will be manipulated to have controllable transmission, while the acoustic waves impinged from the side of zero-index metamaterials will keep a high transmission. We think the proposed design is full of physical significance, which may find potential applications in many fields, like noise cancelation, acoustic imaging, and ultrasound therapy.
Overlap junctions for superconducting quantum electronics and amplifiers
Authors: Bal Mustafa , Long Junling , Zhao Ruichen , Wang Haozhi , Park Sungoh , McRae Corey Rae Harrington , Zhao Tongyu , Lake Russell E. , Monarkha Volodymyr , Simbierowicz Slawomir , Frolov Daniil , Pilipenko Roman , Zorzetti Silvia , Romanenko Alexander , Liu Chuan-Hong , McDermott Robert , Pappas David P.
Published: March 2021

Due to their unique properties as lossless, nonlinear circuit elements, Josephson junctions lie at the heart of superconducting quantum information processing. Previously, we demonstrated a two-layer, submicrometer-scale overlap junction fabrication process suitable for qubits with long coherence times. Here, we extend the overlap junction fabrication process to micrometer-scale junctions. This allows us to fabricate other superconducting quantum devices. For example, we demonstrate an overlap junction-based Josephson parametric amplifier that uses only two layers. This efficient fabrication process yields frequency-tunable devices with negligible insertion loss, a gain of ∼30 dB, and quantum limited noise performance. Compared to other processes, the overlap junction allows for fabrication with minimal infrastructure, high yield, and state-of-the-art device performance.
Iwi (tribal) data collection at a primary health care organisation in Aotearoa
Authors: Enright James (Hemi) , Anderson Anneka , Jansen Rawiri McKree , Murray Jonathan , Brewer Karen , Selak Vanessa , Harwood Matire
Published: March 2021

ABSTRACT INTRODUCTION Indigenous peoples’ rights include the right to self-determine one’s identity. For Māori, this includes self-assignment of ethnicity, and traditional identities such as Iwi (tribe). New Zealand’s Ministry of Health requires health services to collect ethnicity data using standard protocols. Iwi data are also collected by some health services; however, with no health-specific protocols, little is known about Iwi data collection and quality. The National Hauora Coalition (NHC) Primary Healthcare Organisation (PHO) sought to understand Iwi data collection across its network of primary care providers. AIM To understand Iwi data collection at the NHC PHO; specifically, is it being routinely collected, how is it being collected and what are the results? METHODS In 2017, NHC’s general practice clinics were invited to submit their enrolment forms, which capture ethnicity and potentially Iwi information, by e-mail to the audit team. Forms were reviewed to determine whether Iwi information was being collected and if so, what question was being used. Iwi numbers were collated from the annual data extract. RESULTS Thirty-three of a total of 35 clinics (94%) submitted their enrolment forms to the audit team. Nine of the 33 clinics (27%) sought Iwi name/s with a specific question on their enrolment form. Six different ‘Iwi’ questions were used by the nine clinics. The data extract revealed that the NHC had Iwi data for 13% (2672/20,814) of its Māori enrolments. Ngāpuhi were the largest Iwi group at the NHC. DISCUSSION This is the first study to describe the quantity and quality of Iwi data collection in NZ primary care. Standard procedures for collecting, recording and using Iwi data are being developed by the NHC PHO. These could inform national protocols to optimise the quality of Iwi data.