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[en] The experimental study of emittance and brightness measurement for pulsed intense e-beam using the combination of so called 'pepperpot-screen' and 'two-aperture collimator-Rogowski coil' are described. Real time measurements are realized with a camera and data processing system. A non-normalized emittance of ε_2.90 = 361 cm·mrad and brightness of B₉₀ = 1283 A·cm²·rad^-2 are obtained for the pulsed beam of 81-7M-01 accelerator in the National University of Defense Technology

[en] The feasibility of propagating annular IREB in periodic permanent magnetic (PPM) field is studied. The PPM field is calculated first using the finite element magnetic method (FEMM). Then forces acting on IREB's electron in such magnetic field are analyzed by fluid model and the radial force equation in modified Mathieu function form is drawn. Finally a 2.5-D particle in-cell (PIC) simulation code is used to investigate the physical process of the IREB's propagation. It is found that the stable propagation for IREB is relative to not only the beam plasma density and its equilibrium position but also the magnetic field intensity and its space period length. The conclusion is drawn that several kA intense annular electron beam can propagate stably in a guiding PPM

[en] A compact hydrogen plasma gun system was designed and tested. There are two rings of graphite and two rings of Ti hydride between coaxial electrodes. Ti hydride is utilized as a reservoir of hydrogen. The surface flashover is taken advantage to produce plasma. The produced plasma density is 10¹⁰ cm^-3-10¹² cm^-3 in a volume of a column with radius 1-2 cm and length of 60-80 cm. The plasma existing time is over 400 μs

[en] A new type virtual cathode oscillator (VCO) with preliminary e-beam modulation was studied by numerical simulation and experimentally tested. It was shown that the variation of the beam modulation signal leaded to the change of character of vircator. In the vircator scheme, the microwave generated by virtual cathode oscillation was partially fed back to the beam acceleration region to modulate the injected e-beam and so as to improve the performance of the vircator. Changing the length of feedback waveguide resulted in a 8dB variation of the radiated microwave power

[en] The summer Asian–Pacific Oscillation (APO) is a major teleconnection pattern that reflects the zonal thermal contrast between East Asia and the North Pacific in the upper troposphere. The performance of Beijing Climate Center Climate System Models (BCC_CSMs) with different horizontal resolutions, i.e., BCC_CSM1.1 and BCC_CSM1.1(m), in reproducing APO interannual variability, APO-related precipitation anomalies, and associated atmospheric circulation anomalies, is evaluated. The results show that BCC_CSM1.1(m) can successfully capture the interannual variability of the summer APO index. It is also more capable in reproducing the APO’s spatial pattern, compared to BCC_CSM1.1, due to its higher horizontal resolution. Associated with a positive APO index, the northward-shifted and intensified South Asian high, strengthened extratropical westerly jet, and tropical easterly jet in the upper troposphere, as well as the southwesterly monsoonal flow over North Africa and the Indian Ocean in the lower troposphere, are realistically represented by BCC_CSM1.1(m), leading to an improvement in reproducing the increased precipitation over tropical North Africa, South Asia, and East Asia, as well as the decreased precipitation over subtropical North Africa, Japan, and North America. In contrast, these features are less consistent with observations when simulated by BCC_CSM1.1. Regression analysis further indicates that surface temperature anomalies over the North Pacific and the southern and western flanks of the Tibetan Plateau are reasonably reproduced by BCC_CSM1.1(m), which contributes to the substantial improvement in the simulation of the characteristics of summer APO compared to that of BCC_CSM1.1.

[en] Theoretical and particle simulation methods are used to investigate the transportation processes of intense relativistic electron beam (IREBs) guided by low magnetic field. It is shown that in the foilless diode, a magnetic field of tapered profile along the A-K gap can restrain the radial movement of electrons, and the undulation of radial movement is decreased in waveguide. Electrons movement guided by the magnetic field decreasing gradually along the tapered waveguide are also studied, it is found that the radial undulation of electrons is not enlarged, though the magnetic field decrease along the waveguide. A proper profile can reduce the requirement of the guiding magnetic field, it is advantageous to realize the high power microwave devices packed by permanent magnet. (authors)

[en] Highlights: • A delayed feed-forward neural network is constructed. • The normal forms of 1:1 resonance Hopf bifurcation are given and the amplitude of the small signal is enhanced. • New method of image contrast enhancement based on 1:1 Hopf bifurcation is obtained. • Compared with the proposed algorithms, the information entropy of the image are significantly improved. • Numerical experiments show the advantages for processing the low contrast image. - Abstract: This paper is concerned with three neurons feed-forward neural network model and more specifically with the study of dynamical behavior of the codimension one nilpotent singularity and 1:1 resonant Hopf bifurcation and outline possible image processing applications. Three neurons dynamical feed-forward neural networks use cross-coupling and feed-forward-coupling to form an nonlinear dynamic neural oscillator with the time delay. The theoretical basis of the pitchfork and 1:1 resonant Hopf bifurcation of feed-forward neural networks with delay is carried out and the analytical formulas are derived to define the various states of the system. The ultimate goal is to understand the dynamics and seek the application in image processing. It is shown that each of these states has a significant impact on the quality of the resulting image contrast enhancement. As application, aiming at the characteristics of remote sensing images with low-contrast and poor resolution textual information, an image enhancement method is presented. We show theoretically and numerically that the gray scale remote sensing image picture contrast is strongly enhanced even if this one is initially very small. The results show that the algorithm can significantly improve the visual impression of the image. Compared with the proposed algorithms in recent years, the information entropy are significantly improved.

[en] Highlights: • Nano-TiC reinforced René 104 superalloy with reduced defects and improved mechanical properties has been prepared by SLM. • Nano-TiC provides heterogeneous nucleation, which promotes the grain refinement and columnar-to-equiaxed grain transition. • The cracking inhibition is due to the refined grain, reduced HAZ area and equiaxed microstructure. • The improved tensile performance is attributed to the grain refinement and the reduction of cracking density. -- Abstract: The introduction of ceramic nanoparticles enables to inhibit the cracking of additively manufactured “hard-to-weld” nickel-based superalloy. Nevertheless, the mechanisms of cracking elimination have not been formed a consensus understanding. Additionally, the nanoparticles are difficult to be uniformly dispersed due to their high specific surface energy. In this study, TiC-René 104 nanocomposite powder was produced using micron-sized TiC particles by ball milling, and nano-TiC reinforced René 104 superalloy was fabricated by selective laser melting (SLM). The grain refinement and columnar-to-equiaxed grain transition of René 104 superalloy are effectively promoted as a result of the heterogeneous nucleation provided by TiC nanoparticles. The cracking density of as-printed TiC-René 104 is reduced by 83.3%, and the ultimate tensile strength and elongation are improved by 31.3% and 113.9%, respectively. The cracking inhibition is ascribed to the significant grain refinement, the diminishment of HAZ area and the formation of fine equiaxed microstructure. The research supplies a prospective approach to inhibit cracking and strengthen mechanical properties in the additively manufactured nickel-based superalloys with poor weldability.

[en] The modulus gradient of asphalt concrete (AC) layers is an important feature of flexible pavements. The variation of the modulus with depth results from the synthetical effect of material properties, the service time of pavements, loading and environmental conditions. Since the modulus gradient directly affects critical responses and performance of pavements, the determination of the modulus gradient of AC layers is necessary for the evaluation, maintenance and rehabilitation of flexible pavements. This paper aims to propose a method to obtain layer moduli of flexible pavements at different loading frequencies, which include a power function describing the modulus gradient of AC layers. The method utilizes results from a typical nondestructive test in the field applying the falling weight deflectometer and techniques of the fast Fourier transform, finite element model updating, kriging model and artificial intelligence. The method is validated by comparing layer moduli obtained from the proposed method and other backcalculation softwares.