bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Si doping well beyond the Mott transition limit in GaN epilayers grown by plasma-assisted molecular beam epitaxy
Authors: Lingaparthi R , Dharmarasu N , Radhakrishnan K , Zheng Y 
Published: October 2021

Abstract
The effects of Si doping well beyond the Mott transition limit on the structural, electrical, and optical properties of plasma assisted molecular beam epitaxy grown GaN layers were studied. Si doping up to a doping density of <1.0 × 1020 cm−3 resulted in smooth surface morphologies and almost strain free 500 nm thick GaN layers on 50 mm Si (111) substrate. In this doping range, the crystal quality improved with increased Si doping. However, GaN layers with doping density of >1.0 × 1020 cm−3 resulted in rough surface morphology and degraded crystal quality. It also showed higher tensile strain, but did not result in cracking. Irrespective of the surface morphology and structural quality, the sheet resistance systematically decreased with increased carrier concentration up to and beyond the doping density of 1.0 × 1020 cm−3. PL study revealed three distinctive characteristics with Si doping: first, yellow luminescence is absent in Si doped samples— an indication of occupied VGa-ON and CN states in the bandgap; second, a distinctive luminescence peak is observed next to the band edge luminescence (BEL) for the samples doped beyond 2.1 × 1019 cm−3—probably an indication of localization of some of the electrons either at donors or at excitons bound to defects; third, blue shift of the BEL is not matching with the calculated Moss–Burstein shift for doping densities beyond 2.1 × 1019 cm−3—an indication of some of the electrons not occupying higher levels of conduction band, which is consistent with the second observation of localization of electrons near the donors or excitons bound to surface defects.
Quadrupole-octupole collectivity in the Xe, Ba, Ce and Nd isotopic chains described with mean field and beyond approaches
Authors: Rodríguez-Guzmán R , Robledo L M , Nomura K , Hernandez N Cruz 
Published: October 2021

Abstract
The impact of quadrupole and octupole collectivity in the dynamic of low-lying collective states is discussed for a set of Xe, Ba, Ce and Nd isotopes with neutron numbers 54 ⩽ N ⩽ 96. Mean field based methods including pairing are used in our microscopic description along with the Gogny D1M force. Starting with a set of Hartree–Fock–Bogoliubov constrained states we consider dynamic fluctuations of the collective variables by using the generator coordinate method. Related quantities like reduced electromagnetic transition probabilities B(E1) and B(E3) and negative-parity excitation energies and their behavior with neutron number are discussed and compared with the available experimental data. The coupling between the quadrupole and octupole degrees of freedom is found to be rather weak in all the considered nuclei and therefore the properties of the negative parity states can be reasonably well described in terms of the octupole degree of freedom alone. The results of the calculations point towards dynamically enhanced octupole correlations around the ‘octupole magic’ neutron numbers N = 56 and N = 88.
Magnetization reversal, field-induced transitions and H–T phase diagram of Y1−x
Ce
x
CrO3
Authors: Dokala R K , Das S , Weise B , Medwal R , Rawat R S , Thota S 
Published: October 2021

Abstract
We report a systematic study of the magnetic phase diagram in the H–T plane, negative magnetization (NM), exchange interactions and field-induced spin–flop transitions in the distorted perovskite Y1−x
Ce
x
CrO3. Locked AFM and weak-FM configurations in Γ4(G

z
, F

y
, A

x
) phase of YCrO3 (S = 3/2 ground state) unlocks into the Γ2 (F

z
, G

y
, C

x
;

F

z

R

,

C

x

R

) phase of the canted AFM and FM structures with the dilute substitution of Ce (x ⩾ 0.05). The asymmetric and symmetric exchange interaction (J
AS ∼ 0.11 meV and J
S ∼ 0.85 meV) between the trivalent Ce and Cr enable the positive quartic-anisotropy field (

H

K

4

∼ 2.85 × 102 Oe) along with the second order anisotropy field (

H

K

2

∼ 5.93 × 102 Oe). Unlike the pristine YCrO3 compound, the Ce incorporated system exhibits a giant fourth-order anisotropy constant (K
4 = 1.35 × 105 erg/c.c.) due to the asymmetric exchange interaction between the trivalent Ce–Cr which further lifts the free energy of the system and causes lag in the onset of AFM ordering showing the significant thermal hysteresis (ΔT ∼ 10 K) in the field-cooled (FC)-warming measurement protocol as compared to the FC-cooling mode. The H–T phase diagram, mapped from the isothermal magnetization data and differential magnetic susceptibility data with different measurement protocols clearly distinguishes three prominent regions below the T
N (∼150 K), viz (i) long-range canted AFM + weak FM phase (Γ4 (G

z
, F

y
, A

x
)), (ii) Γ24 mixed phase and (iii) robust Γ2 (F

z
, G

y
, C

x
;

F

z

R

,

C

x

R

) AFM + FM phases. Tunable spin–flopped transition (∼ 30 kOe), significant negative exchange-bias field (H
EB ∼ 2.5 kOe), huge coercive field (H
C ∼ 22 kOe) and large NM (ΔM ∼ 280 emu/mole) are the unique characteristic features of the current investigated system.
Remaining useful life prediction for rolling bearings using correlation coefficient and Kullback–Leibler divergence feature selection
Authors: Liang Pan , Song Xudong , Wang Shengqi , Cong Yuyang , Chen Yilin 
Published: October 2021

Abstract
The prediction accuracy of bearing remaining useful life (RUL) is not high due to the unreasonable stage division of bearing performance degradation and the blindness of feature selection. In order to solve this problem, RUL prediction for rolling bearings using Pearson product-moment correlation coefficient (PPMCC) and Kullback–Leibler divergence (KLIC) feature selection is proposed in this paper. First, in order to divide the bearing performance degradation status more accurately, a novel performance degradation state partition method is provided based on t-distributed stochastic neighbor embedding and a k-means clustering algorithm. Second, multi-scale time status feature selection is implemented using PPMCC and KLIC. Finally, the above-proposed feature selection method is validated on the performance degradation data of rolling bearings provided by the University of Cincinnati platform. The results show good and stable effectiveness of the proposed method, and its superiority is demonstrated by comparison with other approaches.
Concentrated thermionic solar cells using graphene as the collector: theoretical efficiency limit and design rules
Authors: Zhang Xin , Sin Ang Yee , Ang Lay Kee , Chen Jincan 
Published: October 2021

Abstract
We propose an updated design on concentrated thermionic emission solar cells, which demonstrates a high solar-to-electricity energy conversion efficiency larger than 10% under 600 suns, by harnessing the exceptional electrical, thermal, and radiative properties of the graphene as a collector electrode. By constructing an analytical model that explicitly takes into account the non-Richardson behavior of the thermionic emission current from graphene, space charge effect in vacuum gap, and the various irreversible energy losses within the subcomponents, we perform detailed characterizations on the conversion efficiency limit and parametric optimum design of the proposed system. Under 800 suns, a maximum efficiency of 12.8% has been revealed, where current density is 3.87 A cm−2, output voltage is 1.76 V, emitter temperature is 1707 K, and collector temperature is 352 K. Moreover, we systematically compare the peak efficiencies of various configurations combining diamond or graphene, and show that utilizing diamond films as an emitter and graphene as a collector offers the highest conversion efficiency, thus revealing the important role of graphene in achieving high-performance thermionic emission solar cells. This work thus opens up new avenues to advance the efficiency limit of thermionic solar energy conversion and the development of next-generation novel-nanomaterial-based solar energy harvesting technology.
Ionic polymer metal composite compression sensors with 3D-structured interfaces
Authors: Histed Rebecca , Ngo Justin , Hussain Omar A , Lapins Chantel K , Fakharian Omid , Leang Kam K , Liao Yiliang , Aureli Matteo 
Published: October 2021

Abstract
In this paper, we report the development of tailored 3D-structured (engineered) polymer-metal interfaces to create enhanced ‘engineered ionic polymer metal composite’ (eIPMC) sensors towards soft, self-powered, high sensitivity strain sensor applications. We introduce a novel advanced additive manufacturing approach to tailor the morphology of the polymer-electrode interfaces via inkjet-printed polymer microscale features. We hypothesize that these features can promote inhomogeneous strain within the material upon the application of external pressure, responsible for improved compression sensing performance. We formalize a minimal physics-based chemoelectromechanical model to predict the linear sensor behavior of eIPMCs in both open-circuit and short-circuit sensing conditions. The model accounts for polymer-electrode interfacial topography to define the inhomogeneous mechanical response driving electrochemical transport in the eIPMC. Electrochemical experiments demonstrate improved electrochemical properties of the inkjet-printed eIPMCs as compared to the standard IPMC sensors fabricated from Nafion polymer sheets. Similarly, compression sensing results show a significant increase in sensing performance of inkjet-printed eIPMC. We also introduce two alternative methods of eIPMC fabrication for sub-millimeter features, namely filament-based fused-deposition manufacturing and stencil printing, and experimentally demonstrate their improved sensing performance. Our results demonstrate increasing voltage output associated to increasing applied mechanical pressure and enhanced performance of the proposed eIPMC sensors against traditional IPMC based compression sensors.
A two-dimensional piezoelectric traveling wave generator using a multi-integer frequency, two-mode method (MIF-TM)
Authors: Hsu Yu-Hsiang , Lin Yu-Min , Lee Chih-Kung 
Published: October 2021

Abstract
In this paper, we report a new method called a multi-integer frequency, two-mode (MIF-TM) to generate multi-directional traveling waves on a square plate. The uniqueness of this driving method is threefold. Firstly, as the two driving frequencies are at or near resonant frequencies of the two bending modes, the driving efficiency can be largely enhanced by using structural resonance. Secondly, as the two actuating areas can sufficiently induce traveling waves, each of them is driven by one of the two driving frequencies. It is possible to generate steady traveling waves by making the two driving frequencies possess a multi-integer relationship and with a phase difference. Thirdly, the direction of the traveling wave can be controlled to propagate toward either the x- or y-direction by designing the location and size of the actuating area. To assist in the design of the MIF-TM traveling wave generator, an analytical model was derived to depict the induction of the traveling waves. Using this analytical model, we designed a piezoelectric traveling wave generator with weight of 2.35 g, dimension of 45 × 45 × 0.4 mm piezoelectric bimorph with four designated electrode pairs. It was verified to be either in the positive or negative direction traveling wave as it was controlled by adjusting the phase difference between the two driving frequencies. Our experimental results demonstrated that the generated x-direction traveling wave can move a 0.3 g object at a speed of 1.48 mm s−1, and the generated y-direction travel wave can move this same object at a speed of 1.36 mm s−1. The design, numerical analysis, finite element analysis, and experimental studies are detailed in this paper.
Experimental characterization and modular modeling of hystereses for smart material actuators
Authors: Yi Sicheng , Zhang Quan , Xu Liang , Wang Tianhong , Li Long 
Published: October 2021

Abstract
In this article, we present a novel modular modeling approach to describe the hystereses for piezoelectric, magnetostrictive and shape memory alloy (SMA) actuators. For the above actuators, the output vs. input loops exhibit varying hystereses under the input signals of the different frequencies and amplitudes. To this end, the experimental characterization is conducted and hysteresis modeling approach is studied. Two characteristic indexes, i.e. loop relative width, loop asymmetry coefficients, are quantitatively analyzed according to the open-loop experiments for the three actuators. Based on the hysteresis phenomenon analyses, different submodels are selected to describe those phenomena. The Prandtl-Ishlinskii submodel is applied for symmetry rate-independent hysteresis identification; the arctangent-polynomial modified Prandtl-Ishlinskii submodel is proposed for asymmetry rate-independent hysteresis identification; infinite impulse response submodel is used for rate-dependent hysteresis identification. Those submodels are selected to construct a cascaded overall model to describe the hysteresis of piezoelectric, magnetostrictive, and SMA actuators. The hysteresis experimental identification results show that, with the proposed phenomenon-based hysteresis modular modeling approach, better performance can be obtained in terms of modeling accuracy and computation time than some other approaches.
Hydrodynamic response time of magnetorheological fluid in valve mode: model and experimental verification
Authors: Kubík M , Šebesta K , Strecker Z , Jeniš F , Goldasz J , Mazůrek I 
Published: October 2021

Abstract
The transient behaviour of magnetorheological (MR) actuators affects their performance in progressive semiactive control suspension systems. The two sources of the time delay between the control signal and damping force are (a) dynamics of MR damper hardware and (b) the MR fluid dynamics. The significant part of the MR fluid response time is the so-called hydrodynamic response time which is connected with the transient flow. Due to the above, the main aim of this paper is to experimentally determine the hydrodynamic response time of MR fluid and present systematic means for characterizing it via computational fluid dynamics (CFD) or analytical tools. The unique measurement method using an in-house patented slit flow rheometer is presented. The essence of the method relies on determining the pressure drop variation with the time spent by the fluid in the MR gap. The experimental determined hydrodynamic response time of MR fluid ranges from 0.4 to 1 ms for a selected gap size and a range of magnetic field stimuli. The results show that the higher the magnetic field, the lower the hydrodynamic response time is. Both CFD and analytical models exhibit similar trends as the experimental data. Moreover, the impact of temperature and gap size was determined. Here, the higher the gap size and temperature of MR fluid, the longer the response time is.
Exceptional points in a topological waveguide-cavity coupled system
Authors: Dong Junhua , Hu Qingmei , Ji Chang-Yin , Zou Bingsuo , Zhang Yongyou 
Published: October 2021

Abstract
Exceptional points (EPs) as branch singularities describe peculiar degeneracies of non-Hermitian systems, widely studied in topological and non-topological optical architectures with introducing gain or loss technically. This work focuses on the EPs in a topological waveguide (TW)-cavity coupled structure, where there is no need to introduce practical gain or loss. The topological cavity contains two degenerate counter-propagation topological whispering gallery modes, whose coupling with the TW leads to the effective gain and loss, responsible for the EP. Such a photonic architecture is designed practically by crystal-symmetry-protected topological photonic insulators based on air rods in conventional dielectric materials. The relevant EP reveals the breaking of the parity-time symmetry, reflected by the change of the transmission-dip number in the optical transmission spectra of the system. Achieving EPs in topological photonic systems possibly opens a new avenue toward robust optical devices with exceptional-point-based unique properties and functionalities.
Fitting ultracold resonances without a fit
Authors: Simoni A 
Published: October 2021

Abstract
We present a numerical procedure allowing one to extract Feshbach resonance parameters from numerical calculations without relying on approximate fitting procedures. Our approach is based on a simple decomposition of the reactance matrix in terms of poles and residual background contribution, and can be applied to the general situation of inelastic overlapping resonances. A simple lineshape for overlapping inelastic resonances, equivalent to known results in the particular cases of isolated and overlapping elastic features, is also rigorously derived.
Multi-messenger emission from the parsec-scale jet of the flat-spectrum radio quasar PKS 1502+106 coincident with high-energy neutrino IceCube-190730A
Authors: Oikonomou Foteini , Petropoulou Maria , Murase Kohta , Tohuvavohu Aaron , Vasilopoulos Georgios , Buson Sara , Santander Marcos 
Published: October 2021

Abstract
On July 30th, 2019 IceCube detected a high-energy astrophysical muon neutrino candidate, IC-190730A with a 67% probability of astrophysical origin. The flat spectrum radio quasar (FSRQ) PKS 1502 +106 is in the error circle of the neutrino. Motivated by this observation, we study PKS 1502+106 as a possible source of IC-190730A. PKS 1502+106 was in a quiet state in terms of UV/optical/X-ray/γ-ray flux at the time of the neutrino alert, we therefore model the expected neutrino emission from the source during its average long-term state, and investigate whether the emission of IC-190730A as a result of the quiet long-term emission of PKS 1502+106 is plausible. We analyse UV/optical and X-ray data and collect additional observations from the literature to construct the multi-wavelength spectral energy distribution of PKS 1502+106. We perform leptohadronic modelling of the multi-wavelength emission of the source and determine the most plausible emission scenarios and the maximum expected accompanying neutrino flux. A model in which the multi-wavelength emission of PKS 1502+106 originates beyond the broad-line region and inside the dust torus is most consistent with the observations. In this scenario, PKS 1502+106 can have produced up to of order one muon neutrino with energy exceeding 100 TeV in the lifetime of IceCube. An appealing feature of this model is that the required proton luminosity is consistent with the average required proton luminosity if blazars power the observed ultra-high-energy-cosmic-ray flux and well below the source's Eddington luminosity. If such a model is ubiquitous among FSRQs, additional neutrinos can be expected from other bright sources with energy ≳ 10 PeV.
AGN Lifetimes in UV-selected Galaxies: A Clue to Supermassive Black Hole-galaxy Coevolution
Authors: Lin Xiaozhi , Xue Yongquan , Fang Guanwen , Fan Lulu , Le Huynh Anh N , Ayubinia Ashraf 
Published: October 2021

Abstract
The coevolution between supermassive black holes (SMBHs) and their host galaxies has been proposed for more than a decade, albeit with little direct evidence about black hole accretion activities regulating galaxy star formation at z > 1. In this paper, we study the lifetimes of X-ray active galactic nuclei (AGNs) in UV-selected red sequence (RS), blue cloud (BC) and green valley (GV) galaxies, finding that AGN accretion activities are most prominent in GV galaxies at z ∼ 1.5–2, compared with RS and BC galaxies. We also compare AGN accretion timescales with typical color transition timescales of UV-selected galaxies. We find that the lifetime of GV galaxies at z ∼ 1.5–2 is very close to the typical timescale when the AGNs residing in them stay in the high-accretion-rate mode at these redshifts; for BC galaxies, the consistency between the color transition timescale and the black hole strong accretion lifetime is more likely to happen at lower redshifts (z < 1). Our results support the scenario where AGN accretion activities govern UV color transitions of host galaxies, making galaxies and their central SMBHs coevolve with each other.
Status of the DOM electronics
Authors: Real D. , Calvo D. , van Beveren V. , Musico P. , Pellegini G. , Jansweijer P. , Colonges S. , Chiarusi T. , Bozza C. , Nicolau C. , Díaz A. , Filippini F. , Benfenati F. 
Published: October 2021

Abstract
The KM3NeT collaboration has already produced electronics to assemble more than one thousand digital optical modules, which have started to be deployed at the bottom of the Mediterranean Sea. An upgrade of the electronics is currently underway, expecting to have a revision of it by end of 2021. Here we describe the main improvements added to the digital optical module electronics, including the new high reliability transceiver in the central logic board and the increased efficiency in the power board.
Self-financed marine protected areas
Authors: Millage Katherine D , Villaseñor-Derbez Juan Carlos , Bradley Darcy , Burgess Matthew G , Lenihan Hunter S , Costello Christopher 
Published: October 2021

Abstract
Marine protected areas (MPAs) are an important tool for conservation but can be victims of their own success—higher fish biomass within MPAs create incentives to poach. This insight underpins the finding that fishing persists in most MPAs worldwide, and it raises questions about MPA monitoring and enforcement. We propose a novel institution to enhance MPA design—a ‘Conservation Finance Area (CFA)’—that utilizes leased fishing zones inside of MPAs, fed by spillover, to finance monitoring and enforcement and achieve greater conservation success. Using a bioeconomic model we show that CFAs can fully finance enforcement, deter illegal fishing, and ultimately maximize fish biomass. Moreover, we show that unless a large, exogenous, and perpetual enforcement budget is available, implementing a CFA in a no-take MPA would always result in higher biomass than without. We also explore real-world enabling conditions, providing a plausible funding pathway to improve outcomes for existing and future MPAs.
Quantum pattern recognition in photonic circuits
Authors: Wang Rui , Hernani-Morales Carlos , Martín-Guerrero José D , Solano Enrique , Albarrán-Arriagada Francisco 
Published: October 2021

Abstract
This paper proposes a machine learning method to characterize photonic states via a simple optical circuit and data processing of photon number distributions, such as photonic patterns. The input states consist of two coherent states used as references and a two-mode unknown state to be studied. We successfully trained supervised learning algorithms that can predict the degree of entanglement in the two-mode state as well as perform the full tomography of one photonic mode, obtaining satisfactory values in the considered regression metrics.
Theory of perturbation of electric potential by a 3D object made of an anisotropic dielectric material
Authors: Lakhtakia Akhlesh , Alkhoori Hamad M , Tsitsas Nikolaos L 
Published: October 2021

Abstract
The extended boundary condition method (EBCM) was formulated for the perturbation of a source electric potential by a 3D object composed of a homogeneous anisotropic dielectric medium whose relative permittivity dyadic is positive definite. The formulation required the application of Green’s second identity to the exterior region to deduce the electrostatic counterpart of the Ewald–Oseen extinction theorem. The electric potential inside the object was represented using a basis obtained by implementing an affine bijective transformation of space to the Gauss equation for the electric field. The EBCM yields a transition matrix that depends on the geometry and the composition of the 3D object, but not on the source potential.