bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk‐averse microgrid cluster switching approach for improving distribution system characteristics considering uncertainties of renewable energy resources
Authors: Saki Reza , Rokrok Esmaeel , Abedini Mohammad , Doostizadeh Meysam
Published: May 2020

Increasing the world‐wide efforts towards low‐carbon economy, highlights the role of renewable energy resources (RESs) in power systems. The volatility of RESs, however, is a major challenge for system operators, and there is need to deal with their uncertainty. Regarding this, microgrids (MGs), as the clusters of different RESs and other distributed energy resources, should take the responsibility of dealing with uncertainty. To do so, a risk‐averse energy management strategy (RA‐EMS) is introduced for distribution systems under the penetration of renewable energy‐based MGs. The status of the connecting switches between clusters and their interaction with the distribution system is examined in several cases. In addition to wind turbine and photovoltaic as RESs, the MGs are equipped with electric vehicles, as another environmentally friendly forms of technology, demand response program, and micro turbines. The uncertainty of renewable generation is modelled via information gap decision theory (IGDT) technique. To validate the effectiveness of the proposed model, it is tested on 94 bus actual Portuguese distribution test system. The results show the importance of MG clustering in improving the techno‐economic characteristics of the distribution system. Also, it is evident from the results that uncertainty of RESs is a crucial factor in MG clustering.
Radar classifications of consecutive and contiguous human gross‐motor activities
Authors: Amin Moeness G. , Guendel Ronny G.
Published: May 2020

The authors consider radar classifications of activities of daily living, which can prove beneficial in fall detection, analysis of daily routines, and discerning physical and cognitive human conditions. They focus on contiguous motion classifications, which follow and commensurate with the human ethogram of possible motion sequences. Contiguous motions can be closely connected with no clear time gap separations. In the proposed approach, they utilise the Radon transform applied to the radar range‐map to detect the translation motion, whereas an energy detector is used to provide the onset and offset times of in‐place motions, such as sitting down and standing up. It is shown that motion classifications give different results when performed forward and backward in time. The number of classes, thereby classification rates, considered by a classifier, is made varying depending on the current motion state and the possible transitioning activities in and out of the state. Two different examples are given to delineate the performance of the proposed approach under typical sequences of human motions.
A plethora of new, magnetic chemically peculiar stars from LAMOST DR4
Authors: Hümmerich S. , Paunzen E. , Bernhard K.
Published: May 2020

Context.Magnetic chemically peculiar (mCP) stars are important to astrophysics because their complex atmospheres lend themselves perfectly to the investigation of the interplay between such diverse phenomena as atomic diffusion, magnetic fields, and stellar rotation. The most up-to-date catalogue of these objects was published a decade ago. Since then, no large scale spectroscopic surveys targeting this group of objects have been carried out. An increased sample size of mCP stars, however, is important for statistical studies.

Aims.The present work is aimed at identifying new mCP stars using spectra collected by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).

Methods.Suitable candidates were selected by searching LAMOST DR4 spectra for the presence of the characteristic 5200 Å flux depression. Spectral classification was carried out with a modified version of the MKCLASS code and the accuracy of the classifications was estimated by comparison with results from manual classification and the literature. Using parallax data and photometry fromGaiaDR2, we investigated the space distribution of our sample stars and their properties in the colour-magnitude diagram.

Results.Our final sample consists of 1002 mCP stars, most of which are new discoveries (only 59 common entries with the Catalogue of Ap, HgMn and Am stars). Traditional mCP star peculiarities have been identified in all but 36 stars, highlighting the efficiency of the code’s peculiarity identification capabilities. The derived temperature and peculiarity types are in agreement with manually derived classifications and the literature. Our sample stars are between 100 Myr and 1 Gyr old, with the majority having masses between 2M⊙and 3M⊙. Our results could be considered as strong evidence for an inhomogeneous age distribution among low-mass (M< 3M⊙) mCP stars; however, we caution that our sample has not been selected on the basis of an unbiased, direct detection of a magnetic field. We identified several astrophysically interesting objects: the mCP stars LAMOST J122746.05+113635.3 and LAMOST J150331.87+093125.4 have distances and kinematical properties in agreement with halo stars; LAMOST J034306.74+495240.7 is an eclipsing binary system (Porb= 5.1435 ± 0.0012 d) hosting an mCP star component; and LAMOST J050146.85+383500.8 was found to be an SB2 system likely comprising of an mCP star and a supergiant component.

Conclusions.With our work, we significantly increase the sample size of known Galactic mCP stars, paving the way for future in-depth statistical studies.
Vortices evolution in the solar atmosphere
Authors: Canivete Cuissa José R. , Steiner Oskar
Published: May 2020

Aims. We study vortex dynamics in the solar atmosphere by employing and deriving the analytical evolution equations of two vortex identification criteria.

Methods. The two criteria used are vorticity and the swirling strength. Vorticity can be biased in the presence of shear flows, but its dynamical equation is well known; the swirling strength is a more precise criterion for the identification of vortical flows, but its evolution equation is not known yet. Therefore, we explore the possibility of deriving a dynamical equation for the swirling strength. We then apply the two equations to analyze radiative magneto-hydrodynamical simulations of the solar atmosphere produced with the CO5BOLD code.

Results. We present a detailed review of the swirling strength criterion and the mathematical derivation of its evolution equation. This equation did not exist in the literature before and it constitutes a novel tool that is suitable for the analysis of a wide range of problems in (magneto-)hydrodynamics. By applying this equation to numerical models, we find that hydrodynamical and magnetic baroclinicities are the driving physical processes responsible for vortex generation in the convection zone and the photosphere. Higher up in the chromosphere, the magnetic terms alone dominate. Moreover, we find that the swirling strength is produced at small scales in a chaotic fashion, especially inside magnetic flux concentrations.

Conclusions. The swirling strength represents an appropriate criterion for the identification of vortices in turbulent flows, such as those in the solar atmosphere. Moreover, its evolution equation, which is derived in this paper, is pivotal for obtaining precise information about the dynamics of these vortices and the physical mechanisms responsible for their production and evolution. Since this equation is available, the swirling strength is now the ideal quantity to study the dynamics of vortices in (magneto-)hydrodynamics.
‘Incantatory’ governance: global climate politics’ performative turn and its wider significance for global politics
Authors: Aykut Stefan C. , Morena Edouard , Foyer Jean
Published: May 2020

The 2015 Paris agreement represents a deep-rooted change in global climate governance. While existing scholarly assessments highlight centralinstitutionalfeatures of the Paris shift, they tend to overlook itssymbolic and discursivedimensions. Our analysis shows that the Paris architecture combines two core elements: an iterative pledge and review process to stimulate global climate action, and a ‘performative’ narrative aimed at aligning actors’ expectations on the prospect of a low-carbon future. We therefore suggest calling it anincantatorysystem of governance. We then examine the origins of the new approach and find that the rise of ‘soft law’ approaches and communicative techniques in global climate governance are both indicative of a broader process: the entry of management culture in international organisations. Against this backdrop, we examine the prospects, limitations and caveats of the new approach and discuss its wider implications for global politics.
60 A/W high voltage GaN avalanche photodiode demonstrating robust avalanche and high gain up to 525 K
Authors: Ji Dong , Ercan Burcu , Benson Garrett , Newaz A. K. M. , Chowdhury Srabanti
Published: May 2020

This paper presents a demonstration of a 278 V GaN avalanche photodiode offering a photoresponsivity of 60 A/W and capable of operating at high temperature with a high gain of 105. The GaN n–i–p diode fabricated on a free-standing GaN substrate showed robust avalanche, which has not been observed on any GaN avalanche photodiodes (APDs) grown on foreign substrates. Both electrical and optical characterization studies were conducted to validate the occurrence of avalanche in these devices. The device showed a positive temperature coefficient of breakdown voltage, which follows the nature of avalanche breakdown. The positive coefficient was measured to be 3.85 × 10−4 K−1 (0.1 V/K) at a measurement temperature ranging from 300 K to 525 K. The avalanche-induced electroluminescence is also reported here in GaN APDs. The diode demonstrated superior performance by simultaneously offering a high photoresponsivity of 60 A/W, a high gain of 105 up to 525 K, and low dark current (1.5 × 10−5 A/cm2), measured at 0.95 × BV following industry standards.
Ultrawide coupled bandgap in hybrid periodic system with multiple resonators
Authors: Gao Yuqiang , Wang Lifeng
Published: May 2020

Mechanical metamaterials can be used to control elastic waves, but it is challenging to obtain multiple or ultrawide bandgaps. A one-dimensional simple periodic system with multi-resonator unit cells can achieve multiple locally resonant bandgaps. A unit cell that comprises multiple cells is called a hybrid unit cell. Two different metamaterials with hybrid unit cells are proposed to achieve a wider coupled bandgap. The first type of metamaterial with a hybrid unit cell comprises two simple cells that have different bandgaps connected by a spring. A new Bragg bandgap appears near the locally resonant bandgaps. By adjusting the spring stiffness, these two types of bandgaps can be coupled to achieve an ultrawide coupled bandgap in a lower frequency range. The second type of metamaterial with a hybrid unit cell comprises two different sub-periodic systems. The bandgaps can be combined to achieve a wider bandgap. With this hybrid periodic system, a wider bandgap can be achieved by designing sub-periodic systems with different bandgaps. In addition, the transmission of a finite periodic system is calculated by the transfer-coefficient method, and the results show that elastic waves can be suppressed in wider frequency range in hybrid periodic systems. This paper provides new ways to design metamaterials with wider and lower bandgaps, which can be used for wide and low-frequency vibration isolation in engineering applications.
Lead palladium zirconate titanate: A room temperature nanoscale multiferroic thin film
Authors: Mishra K. K. , Hernandez Jose A. , Instan Alvaro A. , McCartan Shane J. , Marty Gregg J. , Katiyar Ram S.
Published: May 2020

The discovery of single-phase multiferroic materials and the understanding of intriguing physics of the coupling mechanisms between their spin and polarization are important for the next generation of multifunctional devices. In this work, we report dielectric, ferroelectric, and magnetization results of Pd-substituted room-temperature magnetoelectric multiferroic Pb(Zr0.20Ti0.80)0.7Pd0.3O3 (PZTPd) thin films. Highly c axis oriented PZTPd thin films were grown on {(LaAlO3)0.3(Sr2AlTaO6)0.7} substrates using the pulsed laser deposition technique. These films were phase pure and stabilized in a tetragonal phase. Atomic force microscopic studies indicated a homogeneous distribution of grains on the films' surface with a surface roughness (RQ) of ∼5.4 nm. A large dielectric constant of ∼1780 and a low loss tangent value of ∼0.52 were observed at 1 kHz measured at room temperature. Temperature dependent dielectric studies on Pt/PZTPd/La0.7Sr0.3MnO3 metal–insulator–metal heterostructure capacitors between 80 and 660 K indicated a diffused ferroelectric to paraelectric phase transition around 515 K. The polarization hysteresis loops observed at room temperature were attributed to its ferroelectric behavior. Saturated magnetization hysteresis loop with remanent magnetization of 1.54 emu/cm3 was obtained at room temperature. Ferromagnetic ordering in thin films was found to sustain in the entire temperature range from 5 to 395 K, as revealed from the constant behavior of the dM/dT curve with temperature. The mixed oxidation states of palladium (Pd2+/Pd4+) dispersed in the polar Pb(Zr0.20Ti0.80)O3 matrix were revealed from our high resolution x-ray photoelectron spectroscopic studies and is ascribed to the origin of ferromagnetic ordering in the film. These findings suggest that PZTPd thin films are multiferroic (ferroelectric–ferromagnetic) at room temperature.
The conceptual design of 1-ps time resolution neutron detector for fusion reaction history measurement at OMEGA and the National Ignition Facility
Authors: Arikawa Yasunobu , Ota Masato , Nakajima Makoto , Shimizu Tomoki , Segawa Sadashi , Khoa Phan Thanh Nhat , Sakawa Youichi , Abe Yuki , Morace Alessio , Mirfayzi Seyed Reza , Yogo Akifumi , Fujioka Shinsuke , Nakai Mitsuo , Shiraga Hiroyuki , Azechi Hiroshi , Kodama Ryosuke , Kan Koichi , Frenje Johan , Gatu Johnson Maria , Bose Arijit , Kabadi Neel V. , Sutcliffe Graeme D. , Adrian Patrick , Li Chikang , Séguin Fredrick H. , Petrasso Richard
Published: May 2020

The nuclear burn history provides critical information about the dynamics of the hot-spot formation and high-density fuel-shell assembly of an Inertial Confinement Fusion (ICF) implosion, as well as information on the impact of alpha heating, and a multitude of implosion failure mechanisms. Having this information is critical for assessing the energy-confinement time τE and performance of an implosion. As the confinement time of an ICF implosion is a few tens of picoseconds, less than 10-ps time resolution is required for an accurate measurement of the nuclear burn history. In this study, we propose a novel 1-ps time-resolution detection scheme based on the Pockels effect. In particular, a conceptual design for the experiment on the National Ignition Facility and OMEGA are elaborated upon herein. A small organic Pockels crystal “DAST” is designed to be positioned ∼5 mm from the ICF implosion, which is scanned by a chirped pulse generated by a femto-second laser transmitted through a polarization-maintained optical fiber. The originally linearly polarized laser is changed to an elliptically polarized laser by the Pockels crystal when exposed to neutrons, and the modulation of the polarization will be analyzed. Our study using 35-MeV electrons showed that the system impulse response is 0.6 ps. The response time is orders of magnitude shorter than current systems. Through measurements of the nuclear burn history with unprecedented time resolution, this system will help for a better understanding of the dynamics of the hot-spot formation, high-density fuel-shell assembly, and the physics of thermonuclear burn wave propagation.
Schottky barrier height and modulation due to interface structure and defects in Pt|MgO|Pt heterojunctions with implications for resistive switching
Authors: Niranjan Manish K. , Mamindla Ramesh
Published: May 2020

The modulation of Schottky barrier height (SBH) due to defect migration has been suggested to be an important driving mechanism for resistive switching in metal–oxide–metal structures. Here, we explore the SBH and its modulation due to different interface structures and defects in the Pt|MgO|Pt(001) system using hybrid Heyd–Scuseria–Ernzerhof density functional theory. The computed magnitudes of SBH at Pt|MgO interfaces obtained using the generalized gradient approximation (local density approximation) functional are found to be significantly underestimated as compared to those obtained using hybrid functional. Furthermore, the magnitudes of SBH are found to depend critically on interface structures. In the case of defect-free Pt|MgO interfaces, the p-type SBH is found to be 4.13 eV and 3.04 eV for interfaces having adjacent Pt–O and Pt–Mg bonds, respectively. In addition, the SBH magnitudes are found to exhibit significant variation primarily due to nominal effective charges on interface layers which, in turn, are induced by interface defects such as O and Mg vacancies. The magnitudes of p-type SBH are found to increase (decrease) by ∼1.0–1.5 eV as the ionic layers with charge +1e (−1e) are introduced at the interface. The modulation in SBH due to interface ionic/polar layer is explained using a micro-capacitor model. Furthermore, the SBH is found to shift by ∼0.2 eV with the varying distance of O and/or Mg vacancies from the interface. Our results suggest that fluctuations in experimental resistive switching data in Pt|MgO structures may originate due to fluctuations in SBH induced by changes in interface atomic structure. The study also shows that SBH in Pt|MgO and related structures may be modulated in a controlled way by the insertion of interface polar layers. The lower and upper bounds of the SBH magnitudes are also estimated using a semi-empirical model expressed in terms of parameters such as charge neutrality level, ionization potential, pinning parameter, and metal work function. The quantitative results on the SBH modulation presented in the study may be expected to have important implications for resistive switching phenomenon in Pt|MgO and similar other structures.
Quantitative metrics for evaluating thermonuclear design codes and physics models applied to the National Ignition Campaign
Authors: Dimonte Guy
Published: May 2020

Physics models and design codes for hot dense plasmas undergoing thermonuclear burn are evaluated objectively using statistical metrics that compare the difference between calculations and data relative to the experimental uncertainties. The analysis is applied to the National Ignition Campaign (NIC) because it is relevant, comprehensive, and well documented. The statistics confirm that a key process afflicting NIC performance is mix driven by hydrodynamic instabilities as approximated here using the KL model [G. Dimonte and R. Tipton, Phys. Fluids 18, 085101 (2006)]. New physics models are also presented for instability-driven magnetic fields [B. Srinivasan et al., Phys. Rev. Lett. 108, 165002 (2012)] and the Coulomb logarithm for electron–ion thermal relaxation [G. Dimonte and J. Daligault, Phys. Rev. Lett. 101, 135001 (2008)]. The plasma-generated magnetic fields improve the agreement between code and data in a statistically significant manner by reducing the electron thermal conduction in the hot-spot via the Hall term. The Coulomb logarithm is presented in a numerically practical form that incorporates recent theoretical advances. However, it does not improve the agreement between the code and data because the thermal relaxation is so fast in non-ignited NIC plasmas that the typical 20% error does not change the tight coupling between electrons and ions. Even with these improved physics models, the one-dimensional simulations presented here are not able to describe the high-convergence NIC implosions in a statistically acceptable manner. Of the heroic multi-dimensional simulations of Clark et al. [Phys. Plasmas 23, 056302 (2016)], only those in three-dimensions satisfy the statistical acceptance criterion.
Fingerprinting the vibrational signatures of dopants and defects in a fully random alloy: An ab initio case study of Si, Se, and vacancies in In0.5Ga0.5As
Authors: Jia Haili , Wang Jingyang , Clancy Paulette
Published: May 2020

Correct identification of local configurations of dopants and point defects in random alloys poses a challenge to both computational modeling and experimental characterization methods. In this paper, we propose and implement a computationally efficient approach to address this problem. Combining special quasirandom structures, virtual crystal approximation, and real-space lattice static Green’s functions, we are able to calculate, at moderate computational cost, the local phonon density of states (LPDOSs) of impurities in a random alloy crystal for system sizes, surpassing the capabilities of a conventional, cubic-scaling, density functional theory. We validate this method by showing that our LPDOS predictions of substitutional silicon in GaAs and InAs are in excellent agreement with the experimental data. For the case study, we investigate a variety of local configurations of Si and Se substitutional dopants and cation vacancies in quasirandom In0.5Ga0.5As alloys. In all cases, the impurity LPDOS in a random alloy exhibits qualitatively different signatures from those in the pure binary compounds GaAs and InAs. Specifically, they are characterized by a wide continuous band (rather than narrow discrete peaks) of vibrational modes at frequencies typically higher than the bulk modes, a sign of coupling between localized vibrations of the impurity and those of its random neighboring host atoms. The accuracy and computational cost of this approach open a way to the simulation of impurities in random structures on a large scale and the prediction of vibrational signatures of alloys with defects.
A versatile, multi-laser twin-microscope system for light-sheet imaging
Authors: Keomanee-Dizon Kevin , Fraser Scott E. , Truong Thai V.
Published: May 2020

Light-sheet microscopy offers faster imaging and reduced phototoxicity in comparison to conventional point-scanning microscopy, making it a preferred technique for imaging biological dynamics for durations of hours or days. Such extended imaging sessions pose a challenge, as it reduces the number of specimens that can be imaged in a given day. Here, we present a versatile light-sheet imaging instrument that combines two independently controlled microscope-twins, built so that they can share an ultrafast near-infrared laser and a bank of continuous-wave visible lasers, increasing the throughput and decreasing the cost. To permit a wide variety of specimens to be imaged, each microscope-twin provides flexible imaging parameters, including (i) operation in one-photon and/or two-photon excitation modes, (ii) delivery of one to three light-sheets via a trio of orthogonal excitation arms, (iii) sub-micron to micron imaging resolution, (iv) multicolor compatibility, and (v) upright (with provision for inverted) detection geometry. We offer a detailed description of the twin-microscope design to aid instrument builders who wish to construct and use similar systems. We demonstrate the instrument’s versatility for biological investigation by performing fast imaging of the beating heart in an intact zebrafish embryo, deep imaging of thick patient-derived tumor organoids, and gentle whole-brain imaging of neural activity in behaving larval zebrafish.
Conduction band engineering of Mg2Si by isotropic strain for enhancement of thermoelectric performance: A first-principles study
Authors: Hirayama Naomi , Imai Yoji , Hamada Noriaki
Published: May 2020

Mg2Si has attracted considerable attention as an environmentally friendly thermoelectric material. Previous studies have revealed that the thermoelectric performance of Mg2Si is strongly affected by tensile strain. The present study aims at determining the origin of the structural effect on the thermoelectric properties from the perspective of the effective mass, which allows the quantitative analysis of the strain dependence of the electronic states near the Fermi level. We performed first-principles calculations for Mg2Si with assumed different lattice constants and calculated the Seebeck coefficients and the electrical conductivities based on the obtained electronic band structures within the Boltzmann transport theory. As a result, a lattice constant assumed to be larger than that of the equilibrium state improved the thermoelectric power factor, which is consistent with the findings of previous works. We found that this enhancement of thermoelectric performance originates from a larger effective mass of the bottom conduction band as well as an effective convergence of two conduction bands. The present calculation successfully reproduces the value of an experimental effective mass. We also find the temperature dependences of thermoelectric properties using the relaxation time obtained using experimental data.
Shear-induced ordering in systems with competing interactions: A machine learning study
Authors: Pȩkalski J. , Rządkowski W. , Panagiotopoulos A. Z.
Published: May 2020

When short-range attractions are combined with long-range repulsions in colloidal particle systems, complex microphases can emerge. Here, we study a system of isotropic particles, which can form lamellar structures or a disordered fluid phase when temperature is varied. We show that, at equilibrium, the lamellar structure crystallizes, while out of equilibrium, the system forms a variety of structures at different shear rates and temperatures above melting. The shear-induced ordering is analyzed by means of principal component analysis and artificial neural networks, which are applied to data of reduced dimensionality. Our results reveal the possibility of inducing ordering by shear, potentially providing a feasible route to the fabrication of ordered lamellar structures from isotropic particles.
A physically unclonable function using NV diamond magnetometry and micromagnet arrays
Authors: Kehayias Pauli , Bussmann Ezra , Lu Tzu-Ming , Mounce Andrew M.
Published: May 2020

A physically unclonable function (PUF) is an embedded hardware security measure that provides protection against counterfeiting. Here, we present our work on using an array of randomly magnetized micrometer-sized ferromagnetic bars (micromagnets) as a PUF. We employ a 4μm thick surface layer of nitrogen-vacancy (NV) centers in diamond to image the magnetic field from each micromagnet in the array, after which we extract the magnetic polarity of each micromagnet using image analysis techniques. After evaluating the randomness of the micromagnet array PUF and the sensitivity of the NV readout, we conclude by discussing the possible future enhancements for improved security and magnetic readout.
Highly stable in-fiber integrated silica microresonator
Authors: Yin Jinde , Chen Hao , Zhou Zewen , Wei Wenyin , Zhang Bo , Yu Yang , Jiang Junfeng , Wei Huifeng , Yan Peiguang , Ruan Shuangchen
Published: May 2020

We demonstrate a compact in-fiber integrated microresonator based on a silica microsphere and microstructure fiber. Whispering-gallery-modes (WGMs) are effectively excited through evanescent field coupling between the silica microsphere and one of the input tube waveguides of negative curvature fiber. The WGM spectrum with the Q-factor of ∼2.56 × 103 and the extinction ratio of ∼15.2 dB is achieved. The transmission spectra evolution for 5 h reveals the long-term stability of WGM excitation. The experimental results indicate that the in-fiber integrated resonator has the advantages of high stability, high integration, robustness, alignment-free assembly structure, and low cost, motivating potential applications in the lab-in-fiber platform.
Droplet deformation and breakup in shear flow of air
Authors: Xu Zhikun , Wang Tianyou , Che Zhizhao
Published: May 2020

The deformation and breakup of droplets in airflows is important in many applications of spray and atomization processes. However, the shear effect of airflow has never been reported. In this study, the deformation and breakup of droplets in the shear flow of air is investigated experimentally using high-speed imaging, digital image processing, and particle image velocimetry. We identify a new breakup mode of droplets, i.e., the butterfly breakup, in which the strong aerodynamic pressure on the lower part of the droplet leads to the deflection of the droplet and then the formation of a butterfly-shaped bag. A regime map of the droplet breakup is produced, and the transitions between different modes are obtained based on scaling analysis. The elongation and the fragmentation of the droplet rim are analyzed, and the results show that they are significantly affected by the shear via the formation and the growth of nodes on the rim.
Investigation of asymmetrically pitching airfoil at high reduced frequency
Authors: Thakor Mitesh , Kumar Gaurav , Das Debopam , De Ashoke
Published: May 2020

The expanding application in micro-air vehicles has encouraged many researchers to understand the unsteady flow around a flapping foil at a low Reynolds number. We numerically investigate an incompressible unsteady flow around a two-dimensional pitching airfoil (SD7003) at high reduced frequency (k ≥ 3) in the laminar regime. This study interrogates the effect of different unsteady parameters, namely, amplitude (A), reduced frequency (k), Reynolds number (Re), and asymmetry parameter (S) for pitching motion on the force coefficients. The inviscid theoretical model is utilized to calculate the lift coefficient for sinusoidal motion in the viscous regime, and a comparison is made with the numerical results. The theoretical analysis identifies the influence of the non-circulatory lift over circulatory lift at a high reduced frequency. Furthermore, the results indicate that the reduced frequency (k) and asymmetry parameter (S) have a significant impact on the instantaneous and time-averaged force coefficients as well as on the vortex structure in the wake. Finally, the fast Fourier transformation analysis is carried out over a simulated case with fixed amplitude and Reynolds number for distinct k and S values. The findings confirm that the dominant frequency in the flow (k*) has a direct correlation to the airfoil pitching frequency (k).
Critical inter-defect distance that modulates strength and toughness in defective 2D sp2-lattice
Authors: Hao Tengyuan , Ahmed Tousif , Mou Rownak Jahan , Xu Justin , Brown Shane , Hossain Zubaer M.
Published: May 2020

This paper reveals the existence of a critical separation distance (dc) beyond which the elastic interactions between a pair of monovacancies in graphene or hexagonal boron nitride become inconsequential for the strength and toughness of the defective lattice. This distance is independent of the chirality of the lattice. For any inter-defect distance higher than dc, the lattice behaves mechanically as if there is a single defect. For a distance less than dc, the defect–defect elastic interactions produce distinctive mechanical behavior depending on the orientation (θ) of the defect pair relative to the loading direction. Both strength and toughness of the lattice containing a pair of “interacting monovacancies (iMVs)” are either higher or smaller than that of the lattice containing a pair of “non-interacting monovacancies (nMVs),” suggesting the existence of a critical orientation angle θc. For θ<θc, the smaller the distance between the iMVs, the higher the toughness and strength compared to the lattice containing nMVs, whereas, for θ≥θc, the smaller the separation distance between the iMVs, the smaller the toughness and strength compared to the lattice containing nMVs. The transitional behavior has a negligible dependence on the chirality of the lattice, which indicates that the crystallographic anisotropy has a much weaker influence on toughness and strength compared to the anisotropy induced by the orientation angle itself. These observations underline an important point that the elastic fields emanating from vacancy defects are highly localized and fully contained within a small region of around 1.5 nm radius.
Calculating eigenvalues and eigenvectors of parameter-dependent Hamiltonians using an adaptative wave operator method
Authors: Leclerc Arnaud , Jolicard Georges
Published: May 2020

We propose a wave operator method to calculate eigenvalues and eigenvectors of large parameter-dependent matrices using an adaptative active subspace. We consider a Hamiltonian that depends on external adjustable or adiabatic parameters, using adaptative projectors that follow the successive eigenspaces when the adjustable parameters are modified. The method can also handle non-Hermitian Hamiltonians. An iterative algorithm is derived and tested through comparisons with a standard wave operator algorithm using a fixed active space and with a standard block-Davidson method. The proposed approach is competitive; it converges within a few dozens of iterations at constant memory cost. We first illustrate the abilities of the method on a 4D-coupled oscillator model Hamiltonian. A more realistic application to molecular photodissociation under intense laser fields with varying intensity or frequency is also presented. Maps of photodissociation resonances of H2+ in the vicinity of exceptional points are calculated as an illustrative example.
Improving resolution-sensitivity trade off in sub-shot noise quantum imaging
Authors: Ruo-Berchera I. , Meda A. , Losero E. , Avella A. , Samantaray N. , Genovese M.
Published: May 2020

One of the challenges of quantum technologies is realizing the quantum advantage, predicted for ideal systems, in real applications, which have to cope with decoherence and inefficiencies. In quantum metrology, sub-shot-noise quantum imaging (SSNQI) and sensing methods can provide genuine quantum enhancement in realistic situations. However, wide-field SSNQI schemes realized so far suffer a trade-off between the resolution and the sensitivity gain over a classical counterpart: small pixels or integrating area are necessary to achieve high imaging resolution, but larger pixels allow a better detection efficiency of quantum correlations, which means a larger quantum advantage. Here, we show how the SSNQI protocol can be optimized to significantly improve the resolution without giving up the quantum advantage in sensitivity. We show a linear resolution improvement (up to a factor 3) with respect to the simple protocol used in previous demonstrations.
Ti-doped alumina based reliable resistive switching in sub-
μ
A regime
Authors: Lee Dong Kyu , Kim Gun Hwan , Sohn Hyunchul , Yang Min Kyu
Published: May 2020

We investigated the low current resistive switching behavior using Ti-doped Al2O3 and sub-stoichiometric TaOx layers. The optimized concentrations of Ti and O in each Al2O3 and TaOx layer can make the resistive switching device show the stable retention characteristic and 3-bit operation in the current regime under 1 μA. Doped Ti in the Al2O3 layer generated oxygen vacancies to facilitate fluent resistive switching, and the TaOx layer with an appropriate oxygen concentration played the role of an oxygen reservoir and load resistance for reliable retention and electric pulse compatible characteristics, respectively. We presented the materials optimization processes and comparative resistive switching characteristics in detail.
The relevance of probiotics in Caesarean-born neonates
Authors: Sidjabat Hanna E , Alsaggaf Alaa Mohammed Ali , Gopalakrishna Akshatha , Nadar Evelyn , Irwin Adam , Koorts Pieter
Published: May 2020

There is growing interest in the use of probiotics in neonates. In particular, Lactobacillus rhamnosus, L. acidophilus, Bifidobacterium breve and B. longum have been well studied. Caesarean-section (CS)-born infants often lack Lactobacillus spp. and Bifidobacterium spp., which showed increasing evidence in establishing the neonatal immune system. Furthermore, CS increases the difficulties for mothers in initiating and sustaining breastfeeding. Increasing evidence shows CS-born infants are more susceptible to allergy, infections and chronic inflammatory diseases later in life. The number of CS births has increased continuously, now accounting for 35% of all deliveries Australia wide. In this context, probiotics may have a role in establishing a healthy neonatal gut microbiome.
Earth and field observations underpin metapopulation dynamics in complex landscapes: Near-term study on carabids
Authors: Giezendanner Jonathan , Pasetto Damiano , Perez-Saez Javier , Cerrato Cristiana , Viterbi Ramona , Terzago Silvia , Palazzi Elisa , Rinaldo Andrea
Published: May 2020

Understanding risks to biodiversity requires predictions of the spatial distribution of species adapting to changing ecosystems and, to that end, Earth observations integrating field surveys prove essential as they provide key numbers for assessing landscape-wide biodiversity scenarios. Here, we develop, and apply to a relevant case study, a method suited to merge Earth/field observations with spatially explicit stochastic metapopulation models to study the near-term ecological dynamics of target species in complex terrains. Our framework incorporates the use of species distribution models for a reasoned estimation of the initial presence of the target species and accounts for imperfect and incomplete detection of the species presence in the study area. It also uses a metapopulation fitness function derived from Earth observation data subsuming the ecological niche of the target species. This framework is applied to contrast occupancy of two species of carabids (Pterostichus flavofemoratus,Carabus depressus) observed in the context of a large ecological monitoring program carried out within the Gran Paradiso National Park (GPNP, Italy). Results suggest that the proposed framework may indeed exploit the hallmarks of spatially explicit ecological approaches and of remote Earth observations. The model reproduces well the observed in situ data. Moreover, it projects in the near term the two species’ presence both in space and in time, highlighting the features of the metapopulation dynamics of colonization and extinction, and their expected trends within verifiable timeframes.
Lysophosphatidic acid acyltransferase from the thermophilic bacterium Thermus thermophilus HB8 displays substrate promiscuity
Authors: Ogawa Takuya , Suwanawat Nittikarn , Toyotake Yosuke , Watanabe Bunta , Kawamoto Jun , Kurihara Tatsuo
Published: May 2020

Lysophosphatidic acid acyltransferase is a phospholipid biosynthetic enzyme that introduces a fatty acyl group into the sn-2 position of phospholipids. Its substrate selectivity is physiologically important in defining the physicochemical properties of lipid membranes and modulating membrane protein function. However, it remains unclear how these enzymes recognize various fatty acids. Successful purification of bacterial lysophosphatidic acid acyltransferases (PlsCs) was recently reported and has paved a path for the detailed analysis of their reaction mechanisms. Here, we purified and characterized PlsC from the thermophilic bacterium Thermus thermophilus HB8. This integral membrane protein remained active even after solubilization and purification and showed reactivity toward saturated, unsaturated, and methyl-branched fatty acids, although branched-chain acyl groups are the major constituent of phospholipids of this bacterium. Multiple sequence alignment revealed the N-terminal end of the enzyme to be shorter than that of PlsCs with defined substrate selectivity, suggesting that the shortened N-terminus confers substrate promiscuity.

Abbreviations

ACP: acyl carrier protein; CAPS: N-cyclohexyl-3-aminopropanesulfonic acid; CoA: coenzyme A; CYMAL-6: 6-cyclohexyl-1-hexyl-β-d-maltoside; DDM: n-dodecyl-β-d-maltoside; DTNB: 5,5´-dithiobis(2-nitrobenzoic acid); EPA: eicosapentaenoic acid; G3P: glycerol 3-phosphate; HEPES: N-2-hydroxyethylpiperazine-N´-2-ethanesulfonic acid; LPA: lysophosphatidic acid; MS: mass spectrometry; PA: phosphatidic acid.
Influence of dielectric thickness and electrode structure on the ion wind generation by micro fabricated plasma actuators
Authors: Hink R , Pipa A V , Schäfer J , Caspari R , Weichwald R , Foest R , Brandenburg R
Published: May 2020

Surface dielectric barrier discharges are investigated in order to explore the combined effects of barrier thickness and microstructure of the exposed electrode on the ion wind generation. Actuators with straight and structured high voltage electrodes with characteristic sizes of 200 and 250 µm and dielectric thicknesses of 0.5, 1 and 2 mm are compared. It is observed that: i) actuator efficiency of ion wind generation strongly depends on the applied voltage amplitude; ii) operation voltage depends on the dielectric thickness logarithmically; iii) electrode microstructure slightly increases the dynamic pressure (few percent in maximum), however the effect decreases with thicker dielectrics and smaller electrode structures; iv) the pattern of the most intensive discharge parts as well as the dielectric erosion repeats the regular structure of the electrodes down to 200 µm. Several identical samples are tested during different days to estimate the impact of the air humidity and the degradation of the dielectric. The microscale precision of the sample manufacture was accomplished by a commercial facility for printed circuit boards.
On the rigidity of Zoll magnetic systems on surfaces
Authors: Asselle Luca , Lange Christian
Published: May 2020

In this paper we study rigidity aspects of Zoll magnetic systems on closed surfaces. We characterize magnetic systems on surfaces of positive genus given by constant curvature metrics and constant magnetic functions as the only magnetic systems such that the associated Hamiltonian flow is Zoll, i.e. every orbit is closed, on every energy level below the Mañe critical value. We also prove the persistence of possibly degenerate closed geodesics under magnetic perturbations in different instances.
Single spectrum three-material decomposition with grating-based x-ray phase-contrast CT
Authors: Braig Eva-Maria , Pfeiffer Daniela , Willner Marian , Sellerer Thorsten , Taphorn Kirsten , Petrich Christian , Scholz Josef , Petzold Lisa , Birnbacher Lorenz , Dierolf Martin , Pfeiffer Franz , Herzen Julia
Published: May 2020

Grating-based x-ray phase-contrast imaging provides three simultaneous image channels originating from a single image acquisition. While the phase signal provides direct access to the electron density in tomography, there is additional information on sub-resolutional structural information which is called dark-field signal in analogy to optical microscopy. The additional availability of the conventional attenuation image qualifies the method for implementation into existing diagnostic routines. The simultaneous access to the attenuation coefficient and the electron density allows for quantitative two-material discrimination as demonstrated lately for measurements at a quasi-monochromatic compact synchrotron source. Here, we investigate the transfer of the method to conventional polychromatic x-ray sources and the additional inclusion of the dark-field signal for three-material decomposition. We evaluate the future potential of grating-based x-ray phase-contrast CT for quantitative three-material discrimination for the specific case of early stroke diagnosis at conventional polychromatic x-ray sources. Compared to conventional CT, the method has the potential to discriminate coagulated blood directly from contrast agent extravasation within a single CT acquisition. Additionally, the dark-field information allows for the clear identification of hydroxyapatite clusters due to their micro-structure despite a similar attenuation as the applied contrast agent. This information on materials with sub-resolutional microstructures is considered to comprise advantages relevant for various pathologies.
Increased radioactivity during precipitation measured by the HiSPARC experiment
Authors: van Dam Kasper
Published: May 2020

HiSPARC is an extensive network of cosmic ray detection stations mainly across The Netherlands and United Kingdom. Its primary goal is to analyse cosmic ray air showers by sampling their footprints using multiple detectors. Also the detection rates per single detector are recorded. These 'singles rates’ fluctuate in time. Large fluctuations are caused by precipitation. During rain an excess of 222Rn daughter nuclei, scavenged by raindrops, falls to the ground. This results in an increase in the number of gamma rays from the decay of 214Bi. The excess of events can be described by a simple decay model that takes fluctuations of the rain intensity into account.
On spectral properties of one class difference operators
Authors: Baskakov A G , Garkavenko G V , Yu Glazkova M , Uskova N B
Published: May 2020

In this paper, we analyse basic facts of infinite matrix theory. We construct a similarity transform which allows one to represent matrices in a certain class of 5-th diagonal matrices of a difference operator in a diagonal or block-diagonal form. For such matrices, asymptotic estimates of eigenvalues and eigenvectors are obtained. Such matrices are considered in game theory. They are also used in the study fourth-order difference operators with growing potential. The problem of invariant subspaces is also considered.
Functional model of activity of the fire and rescue unit
Authors: Martinovich N V , Mel’nik A A , Kalach A V , Yu Akulov A
Published: May 2020

The article is devoted to the issue of effective management in fire rescue units of the Ministry of Emergency Situations of Russia based on application of functional modeling. Data on functional model of activity of standard fire rescue unit are given. The example of application of functional modeling and business process management in day-to-day operations of fire rescue units, which allows increasing efficiency of management, is considered. The method of assessing the day-to-day activities of the fire rescue unit based on functional modeling described. Problems in the increase of enhancement of the efficiency in the activity of the fire and rescue units related to the Ministry of Emergency Situations (MES) of Russia as well as similar units that are not involved in the federal group of forces and assets is an ultimately burning problem.
Methodical approach to reducing the dimensionality of the task of requirements substantiation for protection of information systems against unauthorized access in organizational-technical systems
Authors: Meshcheryakova T V , Gulyaev O A , Abdullin A A , Batskikh A V
Published: May 2020

The article proposes a methodological approach to reducing the dimensionality of the problem of forming the requirements for the security of information processed in organizational-technical systems with complex architecture. The methodological approach is based on the structural analysis of graphs that formalize the structural scheme of organizational-technical systems and on the construction of the adjacency matrix of the graph. Using the selected elements of strong connectiveness, which form the clusters of architecture, allows further to solve the problem of formation of requirements to the information protection system against unauthorized access and to go from the architecture of organizational-technical system as a whole to the consideration of individual clusters. In this case, the task of forming requirements is significantly simplified. With the use of the proposed method of clustering the architecture of organizational-technical systems, the problem of forming the sets of information protection of objects of biological activity during molecular-biological and genetic - engineering studies is solved.