General decay of energy to a nonlinear viscoelastic two-dimensional beam

A viscoelastic beam in a two-dimensional space is considered with nonlinear tension. A boundary feedback is applied at the right boundary of the beam to suppress the undesirable vibration. The well-posedness of the problem is established. With the multiplier method, a uniform decay result is proven.

Achieving highly uniform two-dimensional PbI2 flakes for photodetectors via space confined physical vapor deposition

Two-dimensional(2D) PbI_2 flakes have been attracting intensive attention as one potential candidate for the modern optoelectronics. However, suffered from the instability of kinetics-driven growth, the fabricated 2D PbI_2 flakes have a wide dimensional distribution even under the same conditions. Herein, a novel facile space confined physical vapor deposition(PVD) process is provided to synthesize uniform triangle PbI_2 flakes with high quality. The confined space provides a relatively stable growth environment that renders more control on the growth kinetics, leading to highly uniform triangle PbI_2 flakes with the average size of 5 mm and thickness of 17 nm. Moreover, as-fabricated PbI_2-based photodetectors show promising stable and flexible optoelectronic performances to 470 nm light, including high responsivity(0.72 AW^(-1)), large on/off ratio up to 900, fast photoresponse speed(rise time of 13.5 ms and decay time of 20 ms) and high detectivity(1.04×10^(10) Jones). The well-controllable growth of the uniform triangle PbI_2 flakes and the detailed exploration of their optoelectronic properties are particularly valuable for their further practical applications.

Quantitative Rectangular Notch Detection of Laser-induced Lamb Waves in Aluminium Plates with Wavenumber Analysis

It is difficult to quantitatively detect defects by using the time domain or frequency domain features of Lamb wave signals due to their dispersion and multimodal characteristics.Therefore,it is important to discover an intrinsical parameter of Lamb waves that could be used as a damage sensitive feature.In this paper,quantitative defect detection in aluminium plates is carried out by means of wavenumber analysis approach.The wavenumber of excited Lamb wave mode is a fixed value,given a frequency,a thickness and material properties of the target plate.When Lamb waves propagate to the structural discontinuity,new wavenumber components are created by abrupt wavefield change.The new wavenumber components can be identified in the frequency-wavenumber domain.To estimate spatially dependent wavenumber values,a short-space two-dimensional Fourier transform(FT)method is presented for processing wavefield data of Lamb waves.The results can be used to determine the location,size and depth of rectangular notch.The analysis techniques are demonstrated using simulation examples of an aluminium plate with a rectangular notch.Then,the wavenumber analysis method is applied to simulation data that are obtained through a range of notch depths and widths.The results are analyzed and rules of the technique with regards to estimating notch depth are determined.Based on simulation results,guidelines for using the technique are developed.Finally,experimental wavefield data are obtained in aluminium plates with rectangular notches by a full noncontact transceiving method,i.e.,laser-laser method.Band-pass filtering combined with continuous wavelet transform is used to extract a certain frequency component from the full laser-induced wavefield with wide band.Shortspace two-dimensional FT method is used for further processing full wavefield data at a certain frequency to estimate spatially dependent wavenumber values.The consistency of simulation and experimental results shows the effectiveness of proposed wavenumber method for quantitative rectangular notch detection.

Notes on Application of WKB Method

The notes here presented are of the modifications introduced in the application of WKB method.Theproblems of two-and three-dimensional harmonic oscillator potential are revisited by WKB and the new formulationof quantization rule respectively.It is found that the energy spectrum of the radial harmonic oscillator,which isreproduced exactly by the standard WKB method with the Langer modification,is also reproduced exactly without theLanger modification via the new quantization rule approach.An alternative way to obtain the non-integral Maslov indexfor three-dimensional harmonic oscillator is proposed.

Radiation effects of electrons on multilayer FePS3studied with laser plasma accelerator

Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft,but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material(Fe PS3).Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the Fe PS3sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough.The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4-unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that Fe PS3cannot withstand such energetic electron radiation without an essential shield.

The Martingale Hardy Type Inequality for Marcinkiewicz-Fejer Means of Two-dimensional Conjugate Walsh-Fourier Series

The main aim of this paper is to prove that for any 0 〈 p≤ 2/3 there exists a martingale f E Hp such that Marcinkiewicz Fejer means of the two-dimensional conjugate Walsh Fourier series of the martingale f is not uniformly bounded in the space Lp.

Monitoring and engineering interface coupling between monolayer WS_(2)and substrate through controllably introducing interfacial strain

The interface properties in two-dimensional(2D)layered materials and their van der Waals(vdW)homo-/heterostructures are of importance in both uncovering novel physical phenomena and optimizing device performance.Despite considerable research interest and enthusiasm direct toward the interlayer coupling in 2D homo-and heterostructures,there is limited research on the coupling at the 2D layered material-substrate interface.This limitation is due to the challenges in achieving direct detection.Currently,the coupling mechanisms at the 2D layered material-substrate interface is ambiguous,which needs greater attention.In this study,we have systematically investigated the interface coupling between monolayer WS_(2)and its supported substrates using high-temperature and high-vacuum in-situ Raman spectroscopy through monitoring the low-frequency Raman mode of monolayer WS_(2).Our findings reveal that both interfacial spacing and strain can significantly affect the coupling strength between the monolayer WS_(2)and the supported substrate.More notably,we found that the strategic introduction of appropriate interfacial strain can effectively enhance the interface coupling.Consequently,we have succeeded in achieving effective regulation of the sample-substrate coupling via a convenient way of controlling the cooling process during annealing.Our findings contribute to a deeper understanding of the coupling correlation between 2D layered materials and substrates,which is of great significance for the design and optimization of high-performance devices based on 2D layered semiconductors.

A framework to express variant and invariant functional spaces for binary logic

A new framework has been developed to express variant and invariant properties of functions operating on a binary vector space.This framework allows for manipulation of dynamic logic using basic operations and permutations.Novel representations of binary functional spaces are presented.Current ideas of binary functional spaces are extended and additional conditions are added to describe new function representation schemes:F code and C code.Sizes of the proposed functional space representation schemes were determined.It was found that the complete representation for any set of functions operating on a binary sequence of numbers is larger than previously thought.The complete representation can only be described using a structure having a space of size 2^(2n)×2^(n)!for any given space of functions acting on a binary sequence of length n.The framework,along with the proposed coding schemes provides a foundational theory of variant and invariant logic in software and electricelectronic technology and engineering,and has uses in the analysis of the stability of rule-based,dynamic binary systems such as cellular automata.

Characterization of Day–James Spaces and Generalized Day–James Spaces

In this paper, we introduce the definition of generalized Day-James space on Rn （n 〉 2） and give a characterization of it, which extend some known results. In addition, we provide a sufficient and necessary condition for Day-James space, which reappeared Day＇s construction for any two-dimensional normed space to make Birkhoff orthogonality symmetry.

Dynamic spot tracking system based on 2D galvanometer in free space optical communication for short distance

Dynamic tracking of laser spot is a key process in the establishment of free space optical communication. In this paper, a dynamic tracking system was presented. In this system, a two-dimensional （2D） galvanometer was used to change the angle of the optical axis of the incident beam at a certain scanning frequency as optical signal jitter simulator, and another galvanometer was used to track the jitter with quadrant detector （QD） and data processing module to acquire the position information of laser spot. Results indicated that the tracking accuracy of this system mainly composed of 2D galvanometer was as high as 27,8 ~rad, and its linear deviation was less than 0.013. The system could still keep the dynamic tracking of the spot stable when the jitter frequency of the optical signal was less than 1000 Hz. Those results suggested that this system could be suitable for the short distance in free space communication due to its simple structure, easy to control and low cost compared with conventional system.

Numerical investigation of thermal performance of heat loss of parabolic trough receiver

Based on the analysis of computation methods and heat transfer processes of the parabolic trough receiver running in steady state, a two-dimensional empirical model was developed to investigate the thermal performance of heat loss of parabolic trough receivers under steady state equilibrium. A numerical simulation was conducted for the parabolic trough receiver involved in a literature. Comparisons between numerical and experimental results show that the empirical model is accurate enough and can be used to investigate the thermal performance of heat loss of parabolic trough receivers. The thermal performance of heat loss of UVAC3 and the new-generation UVAC2008 was investigated respectively. The simulation results show that selective coatings and annular pressure influence the thermal performance of heat loss of parabolic trough receivers greatly, wind velocity influences the thermal performance of thermal loss of parabolic trough receivers only a little in contrast with the emittance of selective coatings and air pressure in annular space. And the thermal performance of thermal loss of the new-generation parabolic trough receiver has been improved in a large amount.