bluuebunny/crossref_metadata_2025_split huggingface dataset:
Levenberg–Marquardt method for ill-posed inverse problems with possibly non-smooth forward mappings between Banach spaces
Authors: Nhu Vu Huu 
Published: November 2021

Abstract
In this paper, we consider a Levenberg–Marquardt method with general regularization terms that are uniformly convex on bounded sets to solve the ill-posed inverse problems in Banach spaces, where the forward mapping might not Gâteaux differentiable and the image space is unnecessarily reflexive. The method therefore extends the one proposed by Jin and Yang in (2016 Numer. Math.
133 655–684) for smooth inverse problem setting with globally uniformly convex regularization terms. We prove a novel convergence analysis of the proposed method under some standing assumptions, in particular, the generalized tangential cone condition and a compactness assumption. All these assumptions are fulfilled when investigating the identification of the heat source for semilinear elliptic boundary-value problems with a Robin boundary condition, a heat source acting on the boundary, and a possibly non-smooth nonlinearity. Therein, the Clarke subdifferential of the non-smooth nonlinearity is employed to construct the family of bounded operators that is a replacement for the non-existing Gâteaux derivative of the forward mapping. The efficiency of the proposed method is illustrated with a numerical example.
Absorption-dominant microwave shielding properties of Sn0.2Fe2.8O4-graphite-PVDF ternary nanocomposite films
Authors: P Lavanya Rathi , Ponraj Bharathi , S Deepa 
Published: November 2021

Abstract
Absorption-dominant microwave shields are in high demand for mitigating the effect of electromagnetic interference (EMI) on devices and the environment. In this paper, we describe the development of absorption enhanced ternary nanocomposites and their EMI shielding capability. Polymer based shields have been fabricated by dispersing conducting graphite and magnetic spinel ferrite Sn0.2Fe2.8O4 nanoparticles in electroactive polymer polyvinylidene fluoride. Shielding effectiveness (SE) values in the expected range of 10–30 dB in the X-band region, were achieved with as low as 30–50 wt% of pristine graphite and 1–10 wt% of Sn0.2Fe2.8O4. The industrial standard of 99% shielding (SE ⩾ 20 dB) was obtained with 50 wt% of graphite. The composites exhibit absorption as the dominant mechanism of shielding. The percentage SE due to absorption is about 70% and is tuned upwards by the increase in ferrite concentration. The composites were characterized by x-ray diffraction and vibrating sample magnetometry; thermal analysis confirms their stability. The thin, flexible films fabricated by the simple and cost-efficient technique of solution casting will be extremely valuable as wrap-on shields for X-band microwave attenuation.
Low-temperature luminescence in organic-inorganic lead iodide perovskite single crystals
Authors: Zhevstovskikh Irina V , Averkiev Nikita S , Sarychev Maksim N , Semenova Olga I , Tereshchenko Oleg E 
Published: November 2021

Abstract
We present a temperature and laser-power dependent photoluminescence (PL) study of methylammonium lead iodide (CH3NH3PbI3) single crystals in the orthorhombic phase. At temperatures below 140 K, we revealed the multi-component PL emission. In addition to a free exciton with an energy of 1.65 eV, we found emission bands with peaks approximately equal to 1.6 eV, 1.52 eV, and 1.48 eV. Analysis of the thermal evolution of the intensities, peak positions, and linewidths of all the PL bands allowed one to determine their origin. We attributed the PL peak with energy of 1.6 eV to a bound exciton, while the free exciton-bound exciton splitting energy is 50–60 meV. The PL emission with an energy of 1.52 eV can be explained by the donor-acceptor pair (DAP) recombination, where donor and acceptor defects have a depth of about 12 meV and 120 meV, respectively. MA (CH3NH3) interstitials (MA

i
+

) and lead vacancies (V

P
b

2
−

) are the most suitable for the DAP transition to occur in CH3NH3PbI3 crystals. The 1.48 eV PL emission is consistent with the recombination of self-trapped excitons, and interstitial iodine is likely to be an active trap source. We found the variation of the self-trapped depth from 15 meV (at

T
<

80 K) to 53 meV (at

T
>

80 K) with increasing the temperature. Although the multi-component PL emission in CH3NH3PbI3 single crystals appears at low temperatures, defects and excitonic traps that cause this emission can affect the photophysics of hybrid perovskites at higher temperatures.
Higgs production in association with a dark-Z at future electron positron colliders
Authors: Giffin Pierce , Lewis Ian M , Zheng Ya-Juan 
Published: November 2021

Abstract
In recent years there have been many proposals for new electron–positron colliders, such as the circular electron–positron collider, the international linear collider, and the future circular collider in electron–positron mode. Much of the motivation for these colliders is precision measurements of the Higgs boson and searches for new electroweak states. Hence, many of these studies are focused on energies above the hZ threshold. However, there are proposals to run these colliders at the lower W
W threshold and Z-pole energies. In this paper, we study a new search for Higgs physics accessible at lower energies: e
+
e
− → hZ
d, where Z
d is a new light gauge boson such as a dark photon or dark-Z. Such searches can be conducted at the W
W threshold, i.e. energies below the hZ threshold where exotic Higgs decays can be searched for in earnest. Additionally, due to very good angular and energy resolution at future electron–positron colliders, these searches will be sensitive to Z
d masses below 1 GeV, which is lower than the current direct LHC searches. We will show that at

s

=
160

GeV with 10 ab−1, a search for e
+
e
− → hZ
d is sensitive to h − Z − Z
d couplings of δ ∼ 9 × 10−3 and cross sections of

∼
2
−
3

ab for Z
d masses below 1 GeV. The results are similar at

s

=
240

GeV with 5 ab−1. These limits are better than those expected from limits on the HL-LHC limits on Higgs branching ratio into generic non-standard model final states and comparable to meson decay limits.
A geometric calibration approach for an industrial cone-beam CT system based on a low-rank phantom
Authors: Yu Jianqiao , Lu Jian , Sun Yi , Liu Jishun , Cheng Kai 
Published: November 2021

AbstractPrecise alignment of the system scan geometry is crucial to ensure the reconstructed image quality in a cone-beam computed tomography (CT) system. A calibration method that depends on the local features of a multi-sphere phantom is probably affected by local image variations. In addition, multiple projections with circular scanning are usually required by this type of method to derive misaligned parameters. In contrast to previous works, this paper proposes a method that depends on the global symmetric low-rank feature of a novel phantom, which can accurately represent the system geometrical misalignment. All the misaligned parameters of the cone-beam CT system can be estimated from a single perspective direction without circular scanning. Meanwhile, since the global low-rank feature of the phantom is utilized, the proposed method is robust to noise. We study the performance of the proposed method through simulations and real experiments. The experimental results demonstrate that the proposed method can estimate the system geometric parameters accurately, leading to superior image quality, with the modulation transfer function of our method (0.22) higher than that of the competing method (0.13) at the spatial resolution of 10 lp mm−1.
An all-in-one approach for synthesis and functionalization of nano colloidal gold with acetylacetone
Authors: Zhang Li , Zheng Hongcen , Gan Yonghai , Wu Bingdang , Chen Zhihao , Wei Shuangshuang , Zhang Guoyang , Zhang Shujuan , Pan Bingcai , Chen Chuncheng 
Published: November 2021

Abstract
Controllable synthesis, proper dispersion, and feasible functionalization are crucial requirements for the application of nanomaterials in many scenarios. Here, we report an all-in-one approach for the synthesis and functionalization of gold nanoparticles (AuNPs) with the simplest β-diketone, acetylacetone (AcAc). With this approach, the particle size of the resultant AuNPs was tunable by simply adjusting the light intensity or AcAc dosage. Moreover, owing to the capping role of AcAc, the resultant AuNPs could be stably dispersed in water for a year without obvious change in morphology and photochemical property. Formation of ligand to metal charge transfer complexes was found to play an important role in the redox conversion of Au with AcAc. Meanwhile, the moderate complexation ability enables the surface AcAc on the AuNPs to undergo ligand exchange reactions (LER). With the aid of Ag+, the AuNPs underwent LER with glutathione and exhibited enhanced photoluminescence (PL) with a maximum of 22-fold increase in PL intensity. The PL response was linear to the concentration of glutathione in the range of 0–500 μM. Such a LER makes the obtained AuNPs being good imaging probes. To the best of our knowledge, this is the first work on illustrating the roles of AcAc as a multifunctional ligand in fabrication of NPs, which sheds new light on the surface modulation in synthesis of nanomaterials.
One-step combustion synthesis of undoped c-ZrO2 for Cr(VI) removal from aqueous solutions
Authors: Dzhevaga E V , Chebanenko M I , Martinson K D , Lobinsky A A , Popkov V I 
Published: November 2021

Abstract
The active practical application of materials based on cubic zirconium dioxide (c-ZrO2) for catalysis, luminescence, and sorption of heavy metals demands the development of methods for its preparation in a nanostructured form. In this work, nanoparticles of undoped cubic zirconia were obtained by solution combustion method, the features of their structure and morphology were investigated, and the efficiency of their use as a basis for sorbents for the removal of hexavalent chromium Cr(VI) from aqueous solutions was evaluated. Based on XPS, it was established that the stabilization of the high-temperature cubic phase of c-ZrO2 occurred due to oxygen vacancies which were formed during the synthesis by glycine-nitrate combustion. From the results of PXRD and Raman spectroscopy cubic structure of the obtained zirconium dioxide nanoparticles is concluded, the average crystallite size was approximately 2 nm. Adsorption structural analysis and SEM indicated aggregation of c-ZrO2 nanocrystals into primary (45–95 nm) and secondary (submicron) agglomerates. The specific surface of the nanopowder determined by the Brunauer–Emmet–Teller method was 25.4 m2 g−1, the pore volume was 0.1670 cm3 g−1, the major part of which is associated with interparticle porosity. Using kinetic pH-metry, it was found that on the surface of synthesized c-ZrO2, rapidly hydrated aprotic Lewis acid centers predominated, and the point of zero charge was 5.8. The results of the sorption of Cr(VI) from aqueous solutions with a concentration of 48–242 mg l−1 at 25 °C and pH = 5 are described by the Freundlich isotherm (R
2 = 0.971), which corresponds to multilayer adsorption. The maximum adsorption capacity according to Langmuir was 33 mg g−1 or 1.34 mg m−2 per unit area. These results allow us to consider the obtained undoped zirconium dioxide as a promising base for sorbents of heavy metals.
Invariant probabilities for discrete time linear dynamics via thermodynamic formalism
*
Authors: Lopes Artur O , Messaoudi Ali , Stadlbauer Manuel , Vargas Victor 
Published: November 2021

Abstract
We show the existence of invariant ergodic σ-additive probability measures with full support on X for a class of linear operators L : X → X, where L is a weighted shift operator and X either is the Banach space

c

0

(

R

)

or

l

p

(

R

)

for 1 ⩽ p < ∞. In order to do so, we adapt ideas from thermodynamic formalism as follows. For a given bounded Hölder continuous potential

A
:
X
→
R

, we define a transfer operator

L

A

which acts on continuous functions on X and prove that this operator satisfies a Ruelle–Perron–Frobenius theorem. That is, we show the existence of an eigenfunction for

L

A

which provides us with a normalised potential

A

¯

and an action of the dual operator

L

A

¯

*

on the one-Wasserstein space of probabilities on X with a unique fixed point, to which we refer to as Gibbs probability. It is worth noting that the definition of

L

A

requires an a priori probability on the kernel of L. These results are extended to a wide class of operators with a non-trivial kernel defined on separable Banach spaces.
Experiments on intense ion beam formation with an inhomogeneous electric field
Authors: Vybin S S , Skalyga V A , Izotov I V , Golubev S V , Razin S V , Shaposhnikov R A , Kazakov M Yu , Bokhanov A F , Shlepnev S P 
Published: November 2021

Abstract
The high efficiency of a new ion beam extraction system with a strongly inhomogeneous electric field has been experimentally demonstrated. Previously, this approach was proposed and analysed numerically by the authors. The experiment was carried out using a pulsed high-current electron-cyclotron resonance (ECR) ion source SMIS 37 with high frequency (37.5 GHz) and high power (100 kW) microwave plasma heating. The accelerating field strength is increased (when compared to a flat or a quasi-pierced geometry) in the plasma meniscus region due to its inhomogeneity. It allows for the increase of the ion acceleration rate and for expansion of the available range of current densities with effective ion beam formation. The experiment demonstrated the main advantages of this approach, such as: a significant decrease in the optimal accelerating voltage for certain values of current density; a possibility of ion beam formation with previously inaccessible current densities; a significant decrease in the ion flux to the puller in non-optimal modes of ion beam formation. Proton beams with a current density of up to 1.1 A cm−2 were obtained for the first time with an ECR ion source.
Enhancement-mode normally-off β-Ga2O3:Si metal-semiconductor field-effect deep-ultraviolet phototransistor
Authors: Liu Zeng , Zhang Maolin , Yang Lili , Li Shan , Zhang Shaohui , Li Kaikai , Li Peigang , Guo Yufeng , Tang Weihua 
Published: November 2021

Abstract
In this work, a solar-blind ultraviolet (UV) photodetector based on a three-terminal enhancement-mode (E-mode) Si-doped β-Ga2O3 (β-Ga2O3:Si) metal-semiconductor field-effect transistor structure is demonstrated, whose threshold voltage (V
th) and subthreshold swing are 4.04 V and 1.4 V dec−1, respectively. A 400 nm thick β-Ga2O3:Si thin film is prepared on sapphire substrate by using metal-organic chemical vapor deposition method. Controlling the channel currents by the Schottky gate voltage in the dark and under illuminations, the photodetector shows dark current (I
dark) as low as 13.4 pA, photo-to-dark current ratio of 4.85 × 104 and linear dynamic range of 29.6 dB, illuminated by 254 nm UV light of 245 μW cm−2. As the UV light is turned on and off, the output current rise and decay time (τ
r and τ
d) are 420 ms and 350 ms. Moreover, at drain voltage (V
ds) of 5 V and gate voltage (V
gs) of 0 V, the responsivity (R), specific detectivity (D*) and external quantum efficiency are achieved as 74 A W−1, 2.15

×

1014 cm Hz1/2 W−1 (Jones) and 3.6

×

104%, respectively.
Design and experimental evaluation a novel magneto-rheological brake with tooth shaped rotor
Authors: Nguyen Van Bien , Le Hiep Dai , Nguyen Quoc Hung , Duyen Do Qui , Hieu Do Huu Minh , Choi Seung-bok 
Published: November 2021

Abstract
In this study, a novel magnetorheological brake (MRB) with tooth-shape rotor is developed. In this new MRB, traditional cylindrical rotor is replaced by a new one with tooth-shaped rotor. The teeth on the rotor act as multiple magnetic poles of the brake. Two magnetic coils are placed on side-housings of the brake to generate a mutual magnetic field of the MRB. The inner face of each side-housing has tooth shaped features as well. These tooth shaped features interact with the rotor teeth via magnetorheological fluid (MRF) medium. By using the tooth shaped rotor, more interface area between the rotor and the working MRF can be archived, which can improve performance characteristics of the proposed MRB such as compact size, low power consumption and high braking torque. After an introduction of state of the art of MRB development, the schematics and working principle of the MRB with tooth-shaped rotor is proposed. The modeling of the MRB is then derived based on magnetic finite element analysis and Bingham rheological model of MRF. Optimal design of the MRB considering mass and braking torque of the MRB is then conducted. From the optimal design result, it is shown that the mass and power consumption of the proposed MRB are significantly smaller than those of previously developed ones. In details, at high value of the maximum braking torque (100 Nm), the proposed MRB mass is only around 31.3% of the mass of the thin-wall single-coil and 42.6% of the mass of the thin-wall double coil MRB. In addition, at small values of the maximum braking torque (5 Nm), power consumption of the proposed MRB is only around 33% of that of the thin-wall single-coil and 45.5% of that of the thin-wall double coil MRB. Experimental works on prototypes of the proposed MRB are then performed for validation.
Boundary layer state detection using piezoelectric sensors
Authors: Stuber Vincent L , Kotsonis Marios , van der Zwaag Sybrand 
Published: November 2021

Abstract
Two piezoelectric series bimorph sensors were embedded below the skin of a NACA 0012 symmetrical airfoil to detect the local state of the boundary layer during wind tunnel testing. Small vanes piercing the airfoil skin were glued onto the bimorphs providing a mechanical coupling to the local mechanical force fluctuations imparted by the local unsteady boundary layer flow. The state of the boundary layer at the sensor sites was varied by changing the angle of attack. The objective of this work was to establish the ability of this sensor concept to accurately distinguish among typical boundary layer states such as attached laminar flow, turbulent flow and separated flow. The output of the sensor was compared to concurrent time-resolved particle image velocimetry measurements, which served as a validation technique. Using the developed sensor response envelope, a single data point time series of the piezo electrical signal was proven to be sufficient to accurately detect the boundary layer state on classical airfoils in the low Reynolds number regime. In projected future applications, single or arrays of bimorph sensors can be used to map the boundary layer of more complex or morphing shape airfoils. The fast response of the sensor can in principle be utilised in closed-loop flow control systems, aimed at drag reduction or lift enhancement.
Non-Hermitian bulk-boundary correspondence and singular behaviors of generalized Brillouin zone
Authors: Guo Gang-Feng , Bao Xi-Xi , Tan Lei 
Published: November 2021

Abstract
The bulk boundary correspondence, which connects the topological invariant, the continuum band and energies under different boundary conditions, is the core concept in the non-Bloch band theory, in which the generalized Brillouin zone (GBZ), appearing as a closed loop generally, is a fundamental tool to rebuild it. In this work, it can be shown that the recovery of the open boundary energy spectrum by the continuum band remains unchanged even if the GBZ itself shrinks into a point. Contrastively, if the bizarreness of the GBZ occurs, the winding number will become illness. Namely, we find that the bulk boundary correspondence can still be established whereas the GBZ has singularities from the perspective of the energy, but not from the topological invariant. Meanwhile, regardless of the fact that the GBZ comes out with the closed loop, the bulk boundary correspondence cannot be well characterized yet because of the ill-definition of the topological number. Here, the results obtained may be useful for improving the existing non-Bloch band theory.
Generalized Darboux transformation and asymptotic analysis on the degenerate dark-bright solitons for a coupled nonlinear Schrödinger system
Authors: Tian He-Yuan , Tian Bo , Sun Yan , Chen Su-Su 
Published: November 2021

Abstract
In this paper, our work is based on a coupled nonlinear Schrödinger system in a two-mode nonlinear fiber. A (N,m)-generalized Darboux transformation is constructed to derive the Nth-order solutions, where the positive integers N and m denote the numbers of iterative times and of distinct spectral parameters, respectively. Based on the Nth-order solutions and the given steps to perform the asymptotic analysis, it is found that a degenerate dark-bright soliton is the nonlinear superposition of several asymptotic dark-bright solitons possessing the same profile. For those asymptotic dark-bright solitons, their velocities are z-dependent except that one of those velocities could become z-independent under certain condition, where z denotes the evolution dimension. Those asymptotic dark-bright solitons are reflected during the interaction. When a degenerate dark-bright soliton interacts with a nondegenerate/degenerate dark-bright soliton, the interaction is elastic, and the asymptotic bound-state dark-bright soliton with z-dependent or z-independent velocity could take place under certain condition. Our study extends the investigation on the degenerate solitons from the bright soliton case for the scalar equations to the dark-bright soliton case for a coupled system.
High power λ ~ 8.5 μm quantum cascade laser grown by MOCVD operating continuous-wave up to 408 K
Authors: Fei Teng , Zhai Shenqiang , Zhang Jinchuan , Zhuo Ning , Liu Junqi , Wang Lijun , Liu Shuman , Jia Zhiwei , Li Kun , Sun Yongqiang , Guo Kai , Liu Fengqi , Wang Zhanguo 
Published: November 2021

Abstract
Robust quantum cascade laser (QCL) enduring high temperature continuous-wave (CW) operation is of critical importance for some applications. We report on the realization of lattice-matched InGaAs/InAlAs/InP QCL materials grown by metal-organic chemical vapor deposition (MOCVD). High interface quality structures designed for light emission at 8.5 μm are achieved by optimizing and precise controlling of growth conditions. A CW output power of 1.04 W at 288 K was obtained from a 4 mm-long and 10 μm-wide coated laser. Corresponding maximum wall-plug efficiency and threshold current density were 7.1% and 1.18 kA/cm2, respectively. The device can operate in CW mode up to 408 K with an output power of 160 mW.