Frontiers of Physics

ISSN 2095-0462

ISSN 2095-0470(Online)

CN 11-5994/O4

邮发代号 80-965

2019 Impact Factor: 2.502

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2020年, 第15卷 第5期 出版日期:2020-10-15

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Laser ablation assisted spark induced breakdown spectroscopy and its application
Wei-Dong Zhou, Yu-Hui Guo, Ran-Ran Zhang
Frontiers of Physics. 2020, 15 (5): 52201-.  
https://doi.org/10.1007/s11467-020-0969-1

摘要   PDF (1087KB)

Recently, laser ablation assisted spark induced breakdown spectroscopy (LA-SIBS) has been growing rapidly and continue to be extended to a broad range of materials analysis. Characterized by employing a specifically designed high voltage and pulse discharge circuit to generate a spark and used to enhance plasma emission produced by laser ablation, allows direct analysis of materials without prior sample preparation. This paper reviews recent development and application of laser ablation assisted spark induced breakdown spectroscopy for material analysis. Following a summary of fundamentals and instrumentation of the LA-SIBS analytical technique, the development and applications of laser ablation assisted spark induced breakdown spectroscopy for the analysis of conducting materials and insulating materials is described.

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Multi-variable special polynomials using an operator ordering method
Xiang-Guo Meng, Kai-Cai Li, Ji-Suo Wang, Zhen-Shan Yang, Xiao-Yan Zhang, Zhen-Tao Zhang, Bao-Long Liang
Frontiers of Physics. 2020, 15 (5): 52501-.  
https://doi.org/10.1007/s11467-020-0967-3

摘要   PDF (1182KB)

Using an operator ordering method for some commutative superposition operators, we introduce two new multi-variable special polynomials and their generating functions, and present some new operator identities and integral formulas involving the two special polynomials. Instead of calculating complicated partial differential, we use the special polynomials and their generating functions to concisely address the normalization, photocount distributions and Wigner distributions of several quantum states that can be realized physically, the results of which provide real convenience for further investigating the properties and applications of these states.

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Controllably asymmetric beam splitting via gap-induced diffraction channel transition in dual-layer binary metagratings
Yang-Yang Fu, Jia-Qi Tao, Ai-Ling Song, You-Wen Liu, Ya-Dong Xu
Frontiers of Physics. 2020, 15 (5): 52502-.  
https://doi.org/10.1007/s11467-020-0968-2

摘要   PDF (3216KB)

In this work, we designed and studied a feasible dual-layer binary metagrating, which can realize controllable asymmetric transmission and beam splitting with nearly perfect performance. Owing to ingenious geometry configuration, only one meta-atom is required to design for the metagrating system. By simply controlling air gap between dual-layer metagratings, high-efficiency beam splitting can be well switched from asymmetric transmission to symmetric transmission. The working principle lies on gap-induced diffraction channel transition for incident waves from opposite directions. The asymmetric/symmetric transmission can work in a certain frequency band and a wide incident range. Compared with previous methods using acoustic metasurfaces, our approach has the advantages of simple design and tunable property and shows promise for applications in wavefront manipulation, noise control and one-way propagation.

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Progress of quantum molecular dynamics model and its applications in heavy ion collisions
Ying-Xun Zhang, Ning Wang, Qing-Feng Li, Li Ou, Jun-Long Tian, Min Liu, Kai Zhao, Xi-Zhen Wu, Zhu-Xia Li
Frontiers of Physics. 2020, 15 (5): 54301-.  
https://doi.org/10.1007/s11467-020-0961-9

摘要   PDF (11044KB)

In this review article, we first briefly introduce the transport theory and quantum molecular dynamics model applied in the study of the heavy ion collisions from low to intermediate energies. The developments of improved quantum molecular dynamics model (ImQMD) and ultra-relativistic quantum molecular dynamics model (UrQMD), are reviewed. The reaction mechanism and phenomena related to the fusion, multinucleon transfer, fragmentation, collective flow and particle production are reviewed and discussed within the framework of the two models. The constraints on the isospin asymmetric nuclear equation of state and in-medium nucleon–nucleon cross sections by comparing the heavy ion collision data with transport models calculations in last decades are also discussed, and the uncertainties of these constraints are analyzed as well. Finally, we discuss the future direction of the development of the transport models for improving the understanding of the reaction mechanism, the descriptions of various observables, the constraint on the nuclear equation of state, as well as for the constraint on in-medium nucleon–nucleon cross sections.

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Some optimizations on detecting gravitational wave using convolutional neural network
Xiang-Ru Li, Wo-Liang Yu, Xi-Long Fan, G. Jogesh Babu
Frontiers of Physics. 2020, 15 (5): 54501-.  
https://doi.org/10.1007/s11467-020-0966-4

摘要   PDF (1233KB)

This work investigates the problem of detecting gravitational wave (GW) events based on simulated damped sinusoid signals contaminated with white Gaussian noise. It is treated as a classification problem with one class for the interesting events. The proposed scheme consists of the following two successive steps: decomposing the data using a wavelet packet, representing the GW signal and noise using the derived decomposition coefficients; and determining the existence of any GW event using a convolutional neural network (CNN) with a logistic regression output layer. The characteristic of this work is its comprehensive investigations on CNN structure, detection window width, data resolution, wavelet packet decomposition and detection window overlap scheme. Extensive simulation experiments show excellent performances for reliable detection of signals with a range of GW model parameters and signal-to-noise ratios. While we use a simple waveform model in this study, we expect the method to be particularly valuable when the potential GW shapes are too complex to be characterized with a template bank.

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A quantitative assessment of communicating extra-terrestrial intelligent civilizations in the galaxy and the case of FRB-like signals
Bing Zhang
Frontiers of Physics. 2020, 15 (5): 54502-.  
https://doi.org/10.1007/s11467-020-0973-5

摘要   PDF (611KB)

A formula is proposed to quantitatively estimate the signal emission rate of Communicating Extra-Terrestrial Intelligent civilizations (CETIs) in the Galaxy. I suggest that one possible type of CETI signal would be brief radio bursts similar to fast radio bursts (FRBs). A dedicated search for FRB–like artificial signals in the Galaxy for decades may pose a meaningful upper limit on the emission rate of these signals by CETIs. The Fermi-Hart paradox is answered in terms of not having enough observing times for this and other types of signals. Whether humans should send FRB-like signals in the far future is briefly discussed.

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