bluuebunny/crossref_metadata_2025 huggingface dataset:
Emerging opportunities for voltage-driven magneto-ionic control in ferroic heterostructures
Authors: Gu Youdi , Song Cheng , Wang Qian , Hu Weijin , Liu Wei , Pan Feng , Zhang Zhidong
Published: April 2021

Voltage control of magnetism has been considered and proven to be an efficient actuation protocol to boost energy efficiency in a widespread range of spintronic devices. In particular, the study of voltage-induced changes in magnetism by the magneto-ionic effect has rapidly accelerated during the past few years due to the versatile advantages of effective control, non-volatile nature, low-power cost, etc. In this perspective, we briefly outline the recent research progress on the voltage-controlled magneto-ionic effect by using two representative dielectric gating materials [ionic liquids (ILs) and ionic conductors] in different functional solid-state heterostructures and devices, mainly including both the ferroic-order [ferromagnetic, ferroelectric (FE), and multiferroic] oxides and magnetic metal-based heterostructure systems. Within the framework of ferroic oxide heterostructures, we have also extended the IL control to FE materials, clarifying that FE properties can also be tailored by electrostatic and electrochemical methods. Finally, we discuss the challenges and future aspects of magneto-ionics, which would inspire more in-depth studies and promote the practical applications.
Spin-to-orbital angular momentum conversion in symmetric dielectric nanorings
Authors: Liu Yang , Hwang Yongsop , Si Guangyuan , Wang Qian , Wang Dapeng
Published: April 2021

Recently, tremendous remarkable studies on spin–orbit interactions (SOIs) have attracted interest of scientists across the world in various fields. Among contemporary technologies of probing SOI, photonic metasurfaces have become a prevalent tool to guide and steer wavefront of light at the subwavelength scale. Nevertheless, the discretized nanoantennas of metasurfaces have been plagued for the shortcoming of bandwidth. In contrast to the discretized strategy, symmetric nanorings possessing a continuous phase gradient are exploited in this work. Benefiting from lossless dielectric material and nondispersive characteristic of the Pancharatnam–Berry phase principle, the designer nanorings are viable to realize high efficient spin-to-vortex conversion over a wide spectrum. The nanorings also accomplish a high purity of orbit angular momentum mode, which is of vital importance in many applications. Our findings would be beneficial to delve spin-controllable nanodevices and hold promise for applications of atomic manipulation and optical tweezers.
Effects of interfaces on structure and dynamics of water droplets on a graphene surface: A molecular dynamics study
Authors: Maurya Manish , Metya Atanu K. , Singh Jayant K. , Saito Shinji
Published: April 2021

The structure and dynamics of water droplets on a bilayer graphene surface are investigated using molecular dynamics simulations. The effects of solid/water and air/water interfaces on the local structure of water droplets are analyzed in terms of the hydrogen bond distribution and tetrahedral order parameter. It is found that the local structure in the core region of a water droplet is similar to that in liquid water. On the other hand, the local structure of water molecules at the solid/water and air/water interfaces, referred to as the interface and surface regions, respectively, consists mainly of three-coordinated molecules that are greatly distorted from a tetrahedral structure. This study reveals that the dynamics in different regions of the water droplets affects the intermolecular vibrational density of states: It is found that in the surface and interface regions, the intensity of vibrational density of states at ∼50 cm−1 is enhanced, whereas those at ∼200 and ∼500 cm−1 are weakened and redshifted. These changes are attributed to the increase in the number of molecules having fewer hydrogen bonds in the interface and surface regions. Both single-molecule and collective orientation relaxations are also examined. Single-molecule orientation relaxation is found to be marginally slower than that in liquid water. On the other hand, the collective orientation relaxation of water droplets is found to be significantly faster than that of liquid water because of the destructive correlation of dipole moments in the droplets. The negative correlation between distinct dipole moments also yields a blueshifted libration peak in the absorption spectrum. It is also found that the water–graphene interaction affects the structure and dynamics of the water droplets, such as the local water structure, collective orientation relaxation, and the correlation between dipole moments. This study reveals that the water/solid and water/air interfaces strongly affect the structure and intermolecular dynamics of water droplets and suggests that the intermolecular dynamics, such as energy relaxation dynamics, in other systems with interfaces are different from those in liquid water.
Excited states in the adiabatic connection fluctuation-dissipation theory: Recovering missing correlation energy from the negative part of the density response spectrum
Authors: Drwal Daria , Pastorczak Ewa , Pernal Katarzyna
Published: April 2021

The adiabatic connection (AC) theory offers an alternative to the perturbation theory methods for computing correlation energy in the multireference wavefunction framework. We show that the AC correlation energy formula can be expressed in terms of the density linear response function as a sum of components related to positive and negative parts of the transition energy spectrum. Consequently, generalization of the adiabatic connection fluctuation-dissipation theory to electronically excited states is obtained. The component of the linear response function related to the negative-transition energy enters the correlation energy expression with an opposite sign to that of the positive-transition part and is non-negligible in the description of excited states. To illustrate this, we analyze the approximate AC model in which the linear response function is obtained in the extended random phase approximation (ERPA). We demonstrate that AC can be successfully combined with the ERPA for excited states, provided that the negative-excitation component of the response function is rigorously accounted for. The resulting AC0D model, an extension of the AC0 scheme introduced in our earlier works, is applied to a benchmark set of singlet excitation energies of organic molecules. AC0D constitutes a significant improvement over AC0 by bringing the excitation energies of the lowest excited states to a satisfactory agreement with theoretical best estimates, which parallels or even exceeds the accuracy of the n-electron valence state perturbation theory method. For higher excitations, AC0D is less reliable due to the gradual deterioration of the underlying ERPA linear response.
Suppression of the superconducting proximity effect in ferromagnetic-superconducting oxide heterostructures with ion-irradiation
Authors: Kumar Yogesh , Bhatt Harsh , Prajapat C. L. , Singh A. P. , Singh Fouran , Kinane C. J. , Langridge S. , Basu S. , Singh Surendra
Published: April 2021

The effect of ion irradiation on the proximity effect in YBa2Cu3O7−δ/La0.67Sr0.33MnO3 and YBa2Cu3O7−δ/SrTiO3/La0.67Sr0.33MnO3 heterostructures has been investigated using spin-polarized neutron reflectivity experiments. We demonstrate that the magnetization in the ferromagnetic (La0.67Sr0.33MnO3) layer at the interface is correlated with the suppression of the superconductivity in the YBa2Cu3O7−δ layer after irradiation, while the layer structure of the heterostructures remains intact. The evolution of the magnetization of the interfacial ferromagnetic layer studied as a function of temperature for both the irradiated heterostructures shows the absence of the proximity effect observed in the un-irradiated samples. The absence of a proximity effect is attributed to the suppression of the superconductivity, as seen in macroscopic magnetization measurements of the heterostructures after ion irradiation.
Stagnation line due to colliding wall jets of two liquid impinging jets on a horizontal surface
Authors: Mohajer Behzad , Dey Anshuman , Li Ri
Published: April 2021

When two free liquid jets impinge on a planar surface with their wall jets colliding, a stagnation line is formed between the two wall jets. The location and shape of the stagnation line depend on the free jet flow conditions, fluid properties, impingement orientation of each free jet, and relative positioning of the two free jets. Experiments are conducted to observe and measure stagnation lines formed by two free jets impinging on the upper surface of a transparent plate, and a camera is placed under the plate to take the images of stagnation lines. It is found that changing the fluid and the position and orientation of the two jets causes the stagnation line to change. A theoretical model consisting of momentum analysis of a singe wall jet and momentum balance of two wall jets is derived to predict the stagnation line. It is hypothesized that, when two unequal liquid wall jets collide, the stagnation takes place where the momentum balance between the two jets within the thinner thickness is satisfied. Based on the hypothesis, the developed theoretical model shows good agreement with the experimental results.
Vertical
β
-Ga2O3 field plate Schottky barrier diode from metal-organic chemical vapor deposition
Authors: Farzana Esmat , Alema Fikadu , Ho Wan Ying , Mauze Akhil , Itoh Takeki , Osinsky Andrei , Speck James S.
Published: April 2021

Vertical β-Ga2O3 Schottky diodes from metal-organic chemical vapor deposition (MOCVD)-grown epitaxial films are reported in this paper for high-power application devices. The Schottky diode, fabricated with a field termination structure, showed a low differential specific on-resistance of 0.67 mΩ cm2. Furthermore, the MOCVD-grown β-Ga2O3 vertical Schottky diodes exhibited a punch-through breakdown and a higher Baliga's figure-of-merit compared to those from other epitaxial growth methods of similar drift layer thickness. This suggests that the MOCVD growth, supporting high-quality epitaxy, can be promising for high-performance β-Ga2O3-based high-power devices.
THz intersubband absorption in n-type Si1−xGex parabolic quantum wells
Authors: Montanari Michele , Ciano Chiara , Persichetti Luca , Corley Cedric , Baldassarre Leonetta , Ortolani Michele , Di Gaspare Luciana , Capellini Giovanni , Stark David , Scalari Giacomo , Virgilio Michele , De Seta Monica
Published: April 2021

High-quality n-type continuously graded Ge-rich Si1−xGex parabolic quantum wells with different doping levels were grown by using ultrahigh-vacuum chemical vapor deposition on Si(001) substrates. A thorough structural characterization study highlights an ideal parabolic compositional profile. THz intersubband absorption has been investigated in modulation-doped samples and samples directly doped in the wells. The comparison of experimental absorption data and theoretical calculations allowed us to quantify the impact of electron correlation effects on the absorption resonances in the different doping conditions and for electron sheet densities in the (1÷6)×1011 cm−2 range. A single optical resonance is present in modulation doped samples. Its peak energy and line shape are independent of temperature-induced variations of the electron distribution in the subbands up to 300 K, in agreement with the generalized Kohn theorem. This achievement represents a relevant step forward for the development of CMOS compatible optoelectronic devices in the THz spectral range, where thermal charge fluctuations play a key role.
Searching local order parameters to classify water structures of ice Ih, Ic, and liquid
Authors: Doi Hideo , Takahashi Kazuaki Z. , Aoyagi Takeshi
Published: April 2021

Identifying molecular structures of water and ice helps reveal the chemical nature of liquid and solid water. Real-space geometrical information on molecular systems can be precisely obtained from molecular simulations, but classifying the resulting structure is a non-trivial task. Order parameters are ordinarily introduced to effectively distinguish different structures. Many order parameters have been developed for various kinds of structures, such as body-centered cubic, face-centered cubic, hexagonal close-packed, and liquid. Order parameters for water have also been suggested but need further study. There has been no thorough investigation of the classification capability of many existing order parameters. In this work, we investigate the capability of 493 order parameters to classify the three structures of ice: Ih, Ic, and liquid. A total of 159 767 496 combinations of the order parameters are also considered. The investigation is automatically and systematically performed by machine learning. We find the best set of two bond-orientational order parameters, Q4 and Q8, to distinguish the three structures with high accuracy and robustness. A set of three order parameters is also suggested for better accuracy.
Extended aging of Ge–Se glasses below the glass transition temperature
Authors: King Ellyn A. , Sen Sabyasachi , Takeda Wataru , Boussard-Pledel Catherine , Bureau Bruno , Guin Jean-Pierre , Lucas Pierre
Published: April 2021

Germanium selenide glasses of compositions spanning the whole glass-formation range are aged at room temperature for up to 20 years. A prominent enthalpy relaxation process is observed in all glasses, and its structural origin is analyzed by Raman spectroscopy. The structural relaxation is manifested in the Raman spectra as a decrease in the ratio of edge- to corner-sharing GeSe4/2 tetrahedral units. This structural evolution can be explained in terms of configurational entropy and density changes. Changes in Raman features and enthalpy follow an identical stretched exponential relaxation function characteristic of aging in glasses. The compositional dependence of enthalpy relaxation after 20 years is in agreement with kinetic considerations based on the glass transition temperature of each glass. The relaxation behavior and heat capacity curves are consistent with standard glass relaxation models for all compositions. These results indicate that the non-reversing enthalpy obtained by modulated differential scanning calorimetry (MDSC), which suggests the existence of non-aging glasses, is not a reliable measure of the ability of a glass to relax. Instead, it is suggested that an interpretation of MDSC data in terms of complex heat capacity provides a more complete and reliable assessment of the relaxation properties of glasses.
ARABIDOPSIS THALIANA HOMEOBOX GENE 1
controls plant architecture by locally restricting environmental responses
Authors: Ejaz Mahwish , Bencivenga Stefano , Tavares Rafael , Bush Max , Sablowski Robert
Published: April 2021

Significance

A major issue in plant biology is how plants are shaped by the interaction between internal genetic programs—for example, those that form boundaries between leaves and the stem—and environmental signals such as light quality, which induces stem elongation in shade conditions. In many plant species, stem growth is suppressed during the vegetative phase, resulting in a compact whorl of leaves called a rosette. We show that the rosette habit of
Arabidopsis
is conferred by a gene involved in organ boundary formation, together with gibberellin hormone signaling, both of which antagonize genes that mediate organ growth in response to light. In this way, a common type of plant architecture results from localized inhibition of environmentally responsive growth.
Production, composition, and mode of action of the painful defensive venom produced by a limacodid caterpillar,
Doratifera vulnerans
Authors: Walker Andrew A. , Robinson Samuel D. , Paluzzi Jean-Paul V. , Merritt David J. , Nixon Samantha A. , Schroeder Christina I. , Jin Jiayi , Goudarzi Mohaddeseh Hedayati , Kotze Andrew C. , Dekan Zoltan , Sombke Andy , Alewood Paul F. , Fry Bryan G. , Epstein Marc E. , Vetter Irina , King Glenn F.
Published: April 2021

Significance

Venoms of limacodid caterpillars evolved independently to those of previously studied animals, and analysis of their venom therefore provides an opportunity to examine patterns of molecular convergence and divergence underlying the evolution of venom use. We report remarkable convergence in the recruitment of venom peptides between limacodids and other venomous taxa. Like scorpions and spiders, limacodids have weaponized immune system peptides to deter potential predators, although these cecropin-derived venom peptides are more similar in structure and mode of action to the venom peptides of hymenopteran insects. This study reveals a venom system with a unique combination of features not previously reported in other venomous animals and provides insights into the functional basis of venoms of the Limacodidae.
Evolutionary and functional analysis of an NRPS condensation domain integrates β-lactam, ᴅ-amino acid, and dehydroamino acid synthesis
Authors: Wheadon Michael J. , Townsend Craig A.
Published: April 2021

Significance

By applying phylogenetic tools, we infer the ancestral origins of a nonribosomal peptide synthetase (NRPS) condensation (C) domain responsible for β-lactam (antibiotic) synthesis. Subsequent in vitro experiments suggest a mechanism for how this unique synthetic function likely evolved. β-Lactam synthesizing ability appears to have emerged along with an adjacent epimerization (E) domain deletion and in parallel with other C domains whose catalysis presumably share intermediates with β-lactam synthesis, including ᴅ-amino acid and dehydroamino acid synthesis. The implied mechanistic link between β-lactam formation and the latter two C-domain functions can be experimentally tested in the future to discern how evolutionary differences dictate synthetic outcome. These insights may constructively guide protein engineering efforts to introduce potentially valuable structural elements into NPRS products.
Ferroelectricity and multiferroicity in anti–Ruddlesden–Popper structures
Authors: Markov Maxime , Alaerts Louis , Miranda Henrique Pereira Coutada , Petretto Guido , Chen Wei , George Janine , Bousquet Eric , Ghosez Philippe , Rignanese Gian-Marco , Hautier Geoffroy
Published: April 2021

Significance

Ferroelectric materials are of great interest for both applied and fundamental reasons. One of the focuses of the community has been to combine ferroelectricity with other properties such as light absorption or ferromagnetism. Unfortunately, these additional properties have been difficult to add to traditional ferroelectrics such as perovskites, and new families of ferroelectric materials are highly sought. Here, we report on a class of ferroelectric materials offering a geometric mechanism of polar instability and a unique set of properties including the extremely rare combination of ferromagnetic and ferroelectric order.
Adoretus sinicus (Chinese rose beetle).
Authors: García-Moll Alberto
Published: April 2021

Adoretus sinicus is a polyphagous beetle, native to parts of eastern Asia, which has been introduced (probably via the plant trade) widely throughout much of Southeast Asia and many Pacific islands, and has the potential to spread further. It feeds on a broad range of plants and can cause severe damage to crops, ornamental plants and trees in places where it has been introduced. USDA-APHIS (United States Department of Agriculture Animal and Plant Health Inspection Service) included it on the Regulated Plant Pest List (USDA-APHIS, 2000).
Ixora coccinea (flame-of-the-woods).
Authors: Chabert-Llompart José
Published: April 2021

A datasheet on Ixora coccinea covering, as an economically important tree, its taxonomy, importance, silviculture, distribution, biology and ecology, uses, products and pests.
Agave americana (century plant).
Authors: Rojas-Sandov Julissa , Iamonico Duilio
Published: April 2021

A datasheet on Agave americana covering, as an economically important tree, its taxonomy, importance, silviculture, distribution, biology and ecology, uses, products and pests.
Should Nigeria join the European Union’s Economic Partnership Agreement with the other ECOWAS states?
Authors: Igechi Gabriel Ozekhome
Published: April 2021

This debate piece explores the possible consequences for Nigeria in the event that she signs up to the Economic Partnership Agreement (EPA) between the European Union (EU) and the other Economic Community of West African States (ECOWAS) member states. It argues that in a global firmament driven by economic conflict, the struggle for resources and realist economic nationalism – and with cut-throat competition as the norm in international political economy – it will amount to folly for the nation to embrace a partnership whose ramifications are at best murky. The author thus questions whether the EPA signed by ECOWAS with the EU will be favourable to the Nigerian people.
Investigations on piezo actuated micro XY stage for vibration-assisted micro milling
Authors: Prabhu Prasad , Rao Muralidhara
Published: April 2021

Vibration assisted machining is an advanced non-conventional precision machining technique aiming at improving the machining performance by superimposing a small amplitude, high-frequency vibration either on the tool or on the workpiece. This article presents the mechanical design, electromechanical simulation, and experimentation on the developed prototype of the flexural hinged micro XY stage for the vibration-assisted micro-milling system. The micro XY stage comprises three layers of flexural hinge structure surrounding the central parallel kinematic structure. The finite element analysis method is adopted to evaluate the static structural stiffness and harmonic behaviour. Two multilayer piezoelectric stack actuators drive the micro XY stage in X and Y directions. The experimental results show that the micro XY stage has a vibrating work area of 17.06 µm × 17.11 µm with a hysteresis nonlinearity and cross-coupling displacements on both axes. Therefore, an electromechanical model is essential to compensate for the hysteresis behaviour and cross-coupling displacements. Open-loop tracking control experiments determine the accuracy of the developed electromechanical model. Implementing a combined hysteresis and cross-coupling displacement compensation approach into the electromechanical model resulted in an open-loop tracking error of 7% for the synchronised circular path and a maximum deviation of 0.6 µm from the linear path.
Active near-infrared wavefront engineering employing geometric phase metasurfaces combined with phase-change materials
Authors: Fan Junxing , Lei Ting , Yuan Xiaocong
Published: April 2021

In recent years, with the remarkable development of micro–nano technology, phase change materials (PCMs) with superior tunable and nonvolatile functionality are integrated into metasurfaces, which has aroused huge interests among scientific communities. However, the imaginary part of refractive index of PCMs in the crystalline phase is large in the near-infrared region (NIR), leading to the strong absorption of device and limiting the development of the PCMs in the NIR. Here, we propose and investigate the hybrid metasurface with asymmetric double-split rings. We use PCM and silica (SiO2) as the composite dielectric layer, which can efficiently reduce the impact of the high imaginary part of the refractive index PCM in the crystalline phase. Moreover, metasurfaces with two types can obtain two different resonances. Furthermore, by inducing the phase change of the PCM, we can move the short-wavelength resonance peak to the position of another long-wavelength resonance peak. Meanwhile, we can add two sets of different phases to two different types of metasurfaces. Thus, the active metasurface based on the PCM can be used to achieve the active wavefront in the NIR. Hence, the proposed metasurface based on the PCM can be applied in tunable beam switching, reconfigurable holography, and other reconfigurable optical components in the NIR.
Wasserstein stability estimates for covariance-preconditioned Fokker–Planck equations
Authors: Carrillo J A , Vaes U
Published: April 2021

We study the convergence to equilibrium of the mean field PDE associated with the derivative-free methodologies for solving inverse problems that are presented by Garbuno-Inigo et al (2020 SIAM J. Appl. Dyn. Syst.
19 412–41), Herty and Visconti (2018 arXiv:1811.09387). We show stability estimates in the Euclidean Wasserstein distance for the mean field PDE by using optimal transport arguments. As a consequence, this recovers the convergence towards equilibrium estimates by Garbuno-Inigo et al (2020 SIAM J. Appl. Dyn. Syst.
19 412–41) in the case of a linear forward model.
A semi-discrete scheme derived from variational principles for global conservative solutions of a Camassa–Holm system
Authors: Galtung Sondre Tesdal , Raynaud Xavier
Published: April 2021

We define a kinetic and a potential energy such that the principle of stationary action from Lagrangian mechanics yields a Camassa–Holm system (2CH) as the governing equations. After discretizing these energies, we use the same variational principle to derive a semi-discrete system of equations as an approximation of the 2CH system. The discretization is only available in Lagrangian coordinates and requires the inversion of a discrete Sturm–Liouville operator with time-varying coefficients. We show the existence of fundamental solutions for this operator at initial time with appropriate decay. By propagating the fundamental solutions in time, we define an equivalent semi-discrete system for which we prove that there exists unique global solutions. Finally, we show how the solutions of the semi-discrete system can be used to construct a sequence of functions converging to the conservative solution of the 2CH system.
Passivity of Lotka–Volterra and quasi-polynomial systems
Authors: Márton Lőrinc , Hangos Katalin M , Magyar Attila
Published: April 2021

This study approaches the stability analysis and controller design of Lotka–Volterra and quasi-polynomial systems from the perspective of passivity theory. The passivity based approach requires to extend the autonomous system model with a suitable input structure. The condition of passivity for Lotka–Volterra systems is less strict than the classic asymptotic stability criterion. It is shown that each Lotka–Volterra system is feedback equivalent to a passive system and a passifying state feedback controller is proposed. The passivity based approach enables the design of novel state feedback controllers to Lotka–Volterra systems. The asymptotic stability can be achieved by applying an additional diagonal state feedback having arbitrarily small gains. This result was further explored to achieve rate disturbance attenuation in controlled Lotka–Volterra systems. By exploiting the dynamical similarities between the Lotka–Volterra and quasi-polynomial systems, it was shown that the passivity related results, developed for Lotka–Volterra systems, are also valid for a large class of quasi-polynomial systems. The methods and tools developed have been illustrated through simulation case studies.
What’s inside the pink box? A nature of science activity for teachers and students
Authors: Pols Freek
Published: April 2021

Although learning about Nature of Science (NOS) promotes a variety of important outcomes, teachers often lack suitable activities for younger students to effectively address NOS. In this article I elaborate on a NOS activity developed for a teacher professionalisation workshop. The activity is suited for younger students as well, where clear links are made between elements of the activity and how science works.
Improved low-dose positron emission tomography image reconstruction using deep learned prior
Authors: Wang Xinhui , Zhou Long , Wang Yaofa , Jiang Haochuan , Ye Hongwei
Published: April 2021

Positron emission tomography (PET) is a promising medical imaging technology that provides non-invasive and quantitative measurement of biochemical process in the human bodies. PET image reconstruction is challenging due to the ill-poseness of the inverse problem. With lower statistics caused by the limited detected photons, low-dose PET imaging leads to noisy reconstructed images with much quality degradation. Recently, deep neural networks (DNN) have been widely used in computer vision tasks and attracted growing interests in medical imaging. In this paper, we proposed a maximum a posteriori (MAP) reconstruction algorithm incorporating a convolutional neural network (CNN) representation in the formation of the prior. Rather than using the CNN in post-processing, we embedded the neural network in the reconstruction framework for image representation. Using the simulated data, we first quantitatively evaluated our proposed method in terms of the noise-bias tradeoff, and compared with the filtered maximum likelihood (ML), the conventional MAP, and the CNN post-processing methods. In addition to the simulation experiments, the proposed method was further quantitatively validated on the acquired patient brain and body data with the tradeoff between noise and contrast. The results demonstrated that the proposed CNN-MAP method improved noise-bias tradeoff compared with the filtered ML, the conventional MAP, and the CNN post-processing methods in the simulation study. For the patient study, the CNN-MAP method achieved better noise-contrast tradeoff over the other three methods. The quantitative enhancements indicate the potential value of the proposed CNN-MAP method in low-dose PET imaging.
Toward a comparison and an optimization of CT protocols using new metrics of dose and image quality part I: prediction of human observers using a model observer for detection and discrimination tasks in low-dose CT images in various scanning conditions
Authors: Othman Nadia , Simon Anne-Catherine , Montagu Thierry , Berteloot Laureline , Grévent David , Habib Geryes Bouchra , Benkreira Mohamed , Bigand Emeline , Capdeville Sophie , Desrousseaux Julie , Farman Bardia , Garnier Eloise , Gempp Stephanie , Nigoul Jean-Marc , Nomikossoff Natacha , Vincent Marion
Published: April 2021

In the context of reducing the patient dose coming from CT scanner examinations without penalizing the diagnosis, the assessment of both patient dose and image quality (IQ) with relevant metrics is crucial. The present study represents the first stage in a larger work, aiming to compare and optimize CT protocols using dose and IQ new metrics. We proposed here to evaluate the capacity of the Non-PreWhitening matched filter with an eye (NPWE) model observer to be a robust and accurate estimation of IQ. We focused our work on two types of clinical tasks: a low contrast detection task and a discrimination task. We designed a torso-shaped phantom, including Plastic Water® slabs with cylindrical inserts of different diameters, sections and compositions. We led a human observer study with 13 human observers on images acquired in multiple irradiation and reconstruction scanning conditions (voltage, pitch, slice thickness, noise level of the reconstruction algorithm, energy level in dual-energy mode and dose), to evaluate the behavior of the model observer compared to the human responses faced to changing conditions. The model observer presented the same trends as the human observers with generally better results. We rescaled the NPWE model on the human responses by scanning conditions (kVp, pitch, slice thickness) to obtain the best agreement between both observer types, estimated using the Bland-Altman method. The impact of some scanning parameters was estimated using the correct answer rate given by the rescaled NPWE model, for both tasks and each insert size. In particular, the comparison between the dual-energy mode at 74 keV and the single-energy mode at 120 kVp showed that, if the 120 kVp voltage provided better results for the smallest insert at the lower doses for both tasks, their responses were equivalent in many cases.
Design and flow rate improvement of a small aeroengine turbine
Authors: Jiang Z Y , Fan Z L , Qiu M , Yang D W
Published: April 2021

The need of small high thrust-to-weight ratio aeroengine is growing. One way to meet this is higher through flow rate of engine. Higher engine mass flow means higher turbine mass flow. In the paper, a small turbine is designed and then promoted with higher flow rate. First the definition of universal turbine through flow capability is discussed and formulated. Then the design and flow rate promotion process of a turbine is introduced. And three design results are obtained and compared, marked MI, MII, and MIII. Among them, MI is original design result with highest efficiency of 0.8899 but doesn’t meet mass flow requirement. MII and MIII are two retrofitted turbines based on MI both with improved mass flow rate by about 3.40%. Different flow rate improvement methods are implemented for the two turbines. S shape endwall is applied to MII stator shroud and MIII turns down stator blade exit angle a bit. MII has higher efficiency than MIII but through flow capability is in fact lowered. Efficiency decline has been seen in both two redesigned turbines compared to MI. The reason possibly lies in the increased rotor shock loss found by detailed CFD flow analysis. Finally, MII is regarded as the best result of which efficiency is 0.8884.
Study on the influence of hot streak and swirl on the film cooling performance of the leading edge of the guide vane
Authors: ChenXiao  , Wei-lin YI
Published: April 2021

In order to study the impacts of the non-uniform conditions of the combustor exit on the flow loss of the turbine guide blade and the cooling performance of the leading edge film, a hot streak and swirl distribution generation program has been developed to implement the parameterization specification of the non-uniform flow state. In addition, the calculation of this paper is based on GE-E3, the numerical simulation analysis is conducted for the swirl/hot streak of the positive blade on the leading edge of the film cooling guide blade. The results showed that the presence of hot streak increased the non-uniformity of vane heat load and had no effect on vane wall pressure distribution. The presence of swirl changes the pressure distribution on the vane wall, affects the migration form of hot streak in the passage, and reduces the cooling effect of the film cooling on the vane. The temperature at the outlet section of the guide vane is uniform.
Effect of Gradient Layer Number on Microstructure and Property of Laser Deposition TA15/Ti2AlNb Transition Zone
Authors: He Bo , Ying-tong Lin , Yang Guang , Qing-jun Zhou , Xiang-ming Wang
Published: April 2021

3 numerical models of laser deposited TA15/Ti2AlNb gradient composite structure were established to simulate the temperature variation of gradient composite structures with different gradient layers in different regions. Then TA15/Ti2AlNb gradient composite structures with different gradient layers were prepared by laser deposition technology. The microstructure, room-temperature tensile properties and microhardness of the deposited samples were observed by optical microscope, tensile testing machine, scanning electron microscope and microhardness tester. The results showed that as the number of gradient layers increased, the temperature in the deposition process of the transition zone increased, while the microstructure difference in the transition zone decreased gradually. As the number of transition layers increased, the tensile strength decreased, but the elongation after fracture increased. All the fracture locations were in the transition zone, and with the increasing of gradient layers, the fracture location gradually shifted to the Ti2AlNb side. The microhardness of the transition zone increased with the increasing of gradient layers. This study will provide reference for the optimization design of TA15/Ti2AlNb gradient composite structure.
Influence of inlet flow field uniformity on the performance of the nuclear main pump
Authors: Sha Long , Yang Shuhua , Kong Xiangdong , Sun Hui , Pei Lin
Published: April 2021

A test loop system with adjustable spoiler function and visual structure was built in this paper. A PIV test system was adopted to investigate the influence of the uniformity of the inlet flow field on the performance of a nuclear main pump scale model, and the NUMECA software was used to numerically simulate the test cases. The research results show that when the rotation direction of the spoiler blade is opposite to that of the impeller, the greater the deviation of the spoiler blade from the axial angle, the more the pump efficiency and head drop; proper positive pre-rotation will not reduce the pump efficiency, but will increase the pump head; for the same spoiler blade deflection angle, when its structure produces irregular flow field disturbances under non-centrosymmetric conditions, the flow field downstream of it will not produce clear swirling flow, and it will not have more impact on the performance of the pump; the axial velocity distribution uniformity δ and the velocity weighted average angle θ, θ’ have obvious direct effects on efficiency, and in the δ interval of each working condition in this paper (the difference between the maximum value and the minimum value of δ is 0.093), the speed weighted average angle has a greater impact on efficiency.

Nomenclature.

Q Rate of flow

δ Axial velocity distribution uniformity

θ Weighted average angle parameter of velocity

θi Absolute axial velocity angle

θ′ Weighted average angle parameter of velocity

η Efficiency

H Head
Numerical analysis of the static characteristic of orifice-type throttled aerostatic journal bearings
Authors: Zhang X H , Ke C L , Peng N , Xiong L Y , Liu L Q
Published: April 2021

The static characteristic of aerostatic journal bearing was studied by numerically simulating the state non-linear Reynolds equation. The finite difference method was used to solve Reynolds equation in MATLAB programming. The relation-ship between the static characteristics and hydrodynamic effect and hydrostatic effect were analyzed. The results show that the load capacity of bearing is directly proportional to the eccentricity ratio, the rotating speed, the air supply pressure and the diameter of orifices; increasing eccentricity ratio, the rotating speed is conducive to reduce the rotor attitude angle and improve the stability of the rotor; increasing the length diameter ratio of bearing and selecting the appropriate orifice position are beneficial to reduce the air consumption of bearing.
Impact of blade leading edge film coolant on the blade tip phantom cooling
Authors: Li F , Liu Z , Feng Z P
Published: April 2021

Numerical simulations are carried out to predict the tip phantom cooling from blade leading edge (LE) coolant. The impact of spanwise angle of the blade LE film holes on the blade tip phantom cooling are investigated in detail under various the mass flow ratios (MFR) of coolant to mainstream from 0.3% to 1.3%. The results demonstrate that the LE film coolant could help cool the tip. These coolants mainly affect the aerothermal performance of the tip forepart and have little impact on that of the tip rear part. Increasing the coolant MFR has an obvious improvement on the tip phantom cooling level, the area-averaged cooling effectiveness could increase more than 2 times in comparing the cases with a higher MFR and a lower one. The cooling effectiveness on the LE surface first increase then decrease as a result of these coolants lift-off the LE surface with the increasing MFR. However, the LE film holes spanwise angle almost has no impact on the tip phantom cooling level at a lower MFR and even deteriorate the LE heat transfer procedure, where the cooling effectiveness decreases as the film holes spanwise angle increases.
Science and Technology Park as an Urban Element Towards Society Scientific Innovation Evolution
Authors: Almaamory Afnan Tuama , Slik Ghada Al
Published: April 2021

The idea of Science and Technology Parks (STP) emerged in the 1950s. The Parks have accumulated several architectural functions, including research centers, scientific exhibitions and innovator residence, etc. As these Parks gradually spread, some of them were linked to university complexes, while others had independent sites. The STP have been linked to the prosperity of society by providing an environment that fosters a culture of innovation and transforming research and ideas based on innovation into a commercially marketed product. However, the functional architectural concept of the STP remained unclear. The objective of this paper is to clarifying the stages of development of Parks architecture, investigating their activities, their linkage regarding planning and design, and the way they act as means to evolve innovation in societies.
International comparison of noise in areal surface topography measurements
Authors: Vanrusselt Maxim , Haitjema Han , Leach Richard , de Groot Peter
Published: April 2021

An international comparison of surface topography measurement noise was carried out. The comparison involved twelve optical surface topography instruments (focus variation instruments, confocal microscopes and coherence scanning interferometers) from six European research laboratories. The purpose of this comparison was to perform a practical test of the ISO definition and procedures for determining measurement noise on a variety of instruments, and to provide good practice guidance to the user community for quantifying, specifying and interpreting measurement noise. Despite taking steps to enable an optimal comparison by supplying a variety of specimens, where the ‘best’ could be selected and the measurement area was clearly defined, an appropriate comparison of the measurement noise beyond the actual measurement conditions was complex, as the measurement time, speed and lateral resolution were difficult to establish for most of the instruments. The results that could be obtained were: (i) the measurment noise N

M
can be reliably estimated from two measurements, (ii) noise may vary considerably between instruments, even when they have the same measurement principle, (iii) the noise in a practical measurement may be considerably higher than the noise with a levelled flat, and (iv) the ‘rms repeatability’ has little correlation to the noise determined according to the ISO specification standard, and may lead to values that are more than a hundred times smaller.
WSe2/graphene heterojunction synaptic phototransistor with both electrically and optically tunable plasticity
Authors: Sun Yilin , Lin Yuxuan , Zubair Ahmad , Xie Dan , Palacios Tomás
Published: April 2021

The imitation of synaptic plasticity in artificial neuromorphic devices has been widely realized based on memristors, transistors and ion devices. This development of artificial synaptic devices is expected to open up a new era for neuromorphic computing. However, the complicated functions in biological synapse are dependent on the dynamic neural activities with modulated plasticity, which is still very difficult to emulate at the device level. Here, an artificial synaptic transistor based on WSe2/graphene van der Waals heterojunction is demonstrated with both electrically and optically modulated synaptic plasticity. By changing the polarity of applied V
gs and V
ds as well as superimposed gate voltage spikes, both excitatory and inhibitory synaptic plasticity can be realized in a single device. Moreover, due to the asymmetric optical response of WSe2/graphene heterojunction, optical modulation on hysteretic behaviors is achieved and also contributes to the inversion of synaptic plasticity. Hence, this work demonstrates a coordinated regulation on synaptic plasticity under electrical and optical stimuli and provides a multi-dimensional modulation strategy to understand the underlying mechanisms of complicated neuromorphic computing and further develop multifunctional neuromorphic optoelectronics.
Significant perpendicular magnetic anisotropy in room-temperature layered ferromagnet of Cr-intercalated CrTe2
Authors: Huang Meng , Ma Zongwei , Wang Sheng , Li Si , Li Miao , Xiang Junxiang , Liu Ping , Hu Guojing , Zhang Zengming , Sun Zhe , Lu Yalin , Sheng Zhigao , Chen Gong , Chueh Yu-Lun , Yang Shengyuan A , Xiang Bin
Published: April 2021

Magnetic anisotropy is an important characteristic of magnetic materials. Particularly, perpendicular magnetic anisotropy (PMA) is superior for the design of spintronic devices, with the advantages of scalability, endurance, thermal stability, and low switching current density. Although a series of two-dimensional (2D) or quasi-2D layered ferromagnets have been demonstrated, the room temperature intrinsic ferromagnets with PMA is rarely found. Here, we report PMA in a room-temperature layered ferromagnet of Cr-intercalated CrTe2. By self-intercalation of the native Cr atoms, the in-plane anisotropy of CrTe2 can be switched to PMA. Meanwhile, the Cr-intercalated CrTe2 crystal can be easily exfoliated into thin flakes with thickness ∼10 nm. Besides the robust PMA at room temperature, Cr-intercalated CrTe2 also exhibits high saturation magnetization (208 emu cm−3 at 300 K), large anomalous Hall angle (2.23% at 300 K) and giant anomalous Hall factor (∼0.18 at 300 K). These excellent properties are highly desired for applications, and make Cr-intercalated CrTe2 a distinguished candidate among all existing magnetic materials. Our work reveals a promising platform for spintronic devices and offers a new route for controlling the magnetic anisotropy in layered materials.
Initial clinical experience of patient-specific QA of treatment delivery in online adaptive radiotherapy using a 1.5 T MR-Linac
Authors: Yang B , Wong Y S , Lam W W , Geng H , Huang C Y , Tang K K , Law W K , Ho C C , Nam P H , Cheung K Y , Yu S K
Published: April 2021

Purpose. This study aims to evaluate the performance of a commercial 1.5 T MR-Linac by analyzing its patient-specific quality assurance (QA) data collected during one full year of clinical operation. Methods and Materials. The patient-specific QA system consisted of offline delivery QA (DQA) and online calculation-based QA. Offline DQA was based on ArcCHECK-MR combined with an ionization chamber. Online QA was performed using RadCalc that calculated and compared the point dose calculation with the treatment planning system (TPS). A total of 24 patients with 189 treatment fractions were enrolled in this study. Gamma analysis was performed and the threshold that encompassed 95% of QA results (T95) was reported. The plan complexity metric was calculated for each plan and compared with the dose measurements to determine whether any correlation existed. Results. All point dose measurements were within 5% deviation. The mean gamma passing rates of the group data were found to be 96.8 ± 4.0% and 99.6 ± 0.7% with criteria of 2%/2mm and 3%/3mm, respectively. T95 of 87.4% and 98.2% was reported for the overall group with the two passing criteria, respectively. No statistically significant difference was found between adaptive treatments with adapt-to-position (ATP) and adapt-to-shape (ATS), whilst the category of pelvis data showed a better passing rate than other sites. Online QA gave a mean deviation of 0.2 ± 2.2%. The plan complexity metric was positively correlated with the mean dose difference whilst the complexity of the ATS cohort had larger variations than the ATP cohort. Conclusions. A patient-specific QA system based on ArcCHECK-MR, solid phantom and ionization chamber has been well established and implemented for validation of treatment delivery of a 1.5 T MR-Linac. Our QA data obtained over one year confirms that good agreement between TPS calculation and treatment delivery was achieved.