Research on reliability index of a large communication network with domain partition and interconnection

In order to indicate the performances of a large-scale communication network with domain partition and interconnection today, a kind of reliability index weighed by normalized capacity is defined. Based on the route rules of network with domain partition and interconnection, the interconnection indexes among the nodes within the domain and among the domains are given from several aspects. It is expatiated on that the index can thoroughly represent the effect on the reliability index of the objective factor and the subjective measures of the designer, which obeys the route rules of a network with domain partition and interconnection. It is discussed that the defined index is rational and compatible with the traditional index.

Comparison of Small-Scale Actively and Passively Q-Switched Eye-Safe Intracavity Optical Parametric Oscillators at 1.57 μm

The first experimental comparison between the actively and passively Q-switched intracavity optical parametric oscillators (IOPOs) at 1.57μm driven by a small-scale diode-pumped Nd:YVO4 laser are thoroughly presented.It is found that the performances of the two types of IOPOs are complementary.The actively Q-switched IOPO features a shorter pulse duration,a higher peak power,and a superior power and pulse stability.However,in terms of compactness,operation threshold and conversion efficiency,passively Q-switched IOPOs are more attractive.It is further indicated that the passively Q-switched IOPO at 1.57 μm is a promising and cost-effective eye-safe laser source,especially at the low and moderate output levels.In addition,instructional improvement measures for the two types of IOPOs are also summarized.

Compact and Highly Efficient Passively Q-Switched Intracavity KTA-OPO at 1.53 and 3.47 μm

Both the signal(1.53µm)and idler(3.47µm)performances of a KTA−based optical parametric oscillator(OPO)are presented.The KTA-OPO is intracavity driven by a diode-pumped Nd:YVO_(4)/Cr:YAG passively Q−switched laser with a quite compact configuration.The signal and idler average output powers up to 941 and 583 mW,respectively,have been achieved,corresponding to an improved diode-to-idler conversion efficiency of 6.5%and a diode-to-OPO(signal+idler)conversion efficiency of 16.9%.At different pump levels,the signal pulse duration and repetition rate are detected to be in the range of 1.8–3.2 ns and 13–112 kHz,respectively.Moreover,near diffraction limited and Gaussian type beam profiles at 1.53 and 3.47µm are also observed.

Preparation of wearable Al-20Pb alloy by powder milling and extrusion densification

Composite powder of Al-20Pb alloy was prepared by mechanical milling. The microstructure of the powder was analyzed by electronic probe microscopy. Compaction of the powder was also performed. The results show that after ball milling for 6h, the composite powder possesses fine laminar structures, good plasticity, and it is easy to densify. By extruding the composite powder ball milled for 6h with an extrusion ratio of 4, the Al-20Pb alloy with a relative density of 97%, a porosity of 3% and fine and homogenously distributed Pb phase was obtained. The results of wear and friction test indicate that a lubricating layer with a friction coefficient of about 0.4 forms on the friction surface, and the wear model is slight oxidation wear.

Layered heuristic algorithm for multiple restriction routes

A layered algorithm by bidirectional searching is proposed in this paper to solve the problem that it is difficult and time consuming to reach an optimal solution of the route search with multiple parameter restrictions for good quality of service. Firstly, a set of reachable paths to each intermediate node from the source node and the sink node based on adjacent matrix transformation are calculated respectively. Then a temporal optimal path is selected by adopting the proposed heuristic method according to a non-linear cost function. When the total number of the accumulated nodes by bidirectional searching reaches n-2, the paths from two directions to an intermediate node should be combined and several paths via different nodes from the source node to the sink node can be obtained, then an optimal path in the whole set of paths can be taken as the output route. Some simulation examples are included to show the effectiveness and efficiency of the proposed method. In addition, the proposed algorithm can be implemented with parallel computation and thus, the new algorithm has better performance in time complexity than other algorithms. Mathematical analysis indicates that the maximum complexity in time, based on parallel computation, is the same as the polynomial complexity of O(kn2-3kn+k), and some simulation results are shown to support this analysis.

A Novel Low-frequency Radio Astronomical Observation Array(1~90 MHz)and its First Light

The extremely low frequency(f<40 MHz)is a very important frequency band for modern radio astronomy observations.It is also a key frequency band for solar radio bursts,planetary radio bursts,fast radio bursts detected in the lunar space electromagnetic environment,and the Earth’s middle and upper atmosphere with low dispersion values.In this frequency band,the solar stellar activity,the early state of the universe,and the radiation characteristics of the planetary magnetosphere and plasma layer can be explored.Since there are few observations with effective spatial resolution in the extremely low frequency,it is highly possible to discover unknown astronomical phenomena on such a band in the future.In conjunction with low frequency radio observation on the far side of the Moon,we initially set up a novel low-frequency radio array in the Qitai station of Xinjiang Astronomical Observatory deep in Tianshan Mountains,Xinjiang,China on 2021 August 23.The array covers an operating frequency range of 1~90 MHz with a sensitivity of-78 dBm/125kHz,a dynamic range of 72 dB,and a typical gain value of 6 dBi,which can realize unattended all-weather observations.The two antennas due south of the Qitai Low-Frequency Radio Array were put into trial observations on 2021 May 28,and the very quiet electromagnetic environment of the station has been confirmed.So far,many solar radio bursts and other foreign signals have been detected.The results show that this novel low frequency radio array has the advantages of good performance,strong direction,and high antenna efficiency.It can play a unique role in Solar Cycle 25,and has a potential value in prospective collaborative observation between the Earth and space for extremely low frequency radio astronomy.

Progress of Jinping Underground laboratory for Nuclear Astrophysics(JUNA)

Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.

Development and Evaluation of Gold 3D Cylindrical Nanoelectrode Ensembles

Gold 3D cylindrical nanoelectrode ensembles （NEEs）, 100 nm in diameter and 500 nm in length were prepared by electroless template synthesis in polycarbonate filter membranes, followed by selective controlled chemical etching. The morphology of the nanowires and cylindrical NEEs was imaged by scanning electron microscopy. The protruding nanoelectrodes were in good parallel order. EDX study showed that the nanoelectrode elements consisted of pure gold. The electrochemical evaluation of the 3D electrodes was conducted using the well known [Fe（CN）6]^3-/[Fe（CN）6]^4- couple. Cyclic voltammgrams （CV） show a very low double layer charging current and a higher ratio of signal to background current than 2D disc NEEs. Electrochemical impedance spectroscopy （EIS） indicates that the 3D cylindrical NEEs effectively accelerate the charge transfer process, which is in consistent with the results of CV. The linear relationship with a slope of 0.5 between lg Ipc and lg v shows that linear diffusion is dominant on the 3D cylindrical NEEs at conventional scan rates.