Topological insulator Sb₂Te₃ has the advantage of broadband saturable absorption from the visible to the infrared bands. Herein, the two-dimensional material Sb₂Te₃ saturable absorber (SA) of the topological insulator family was first applied experimentally in a wideband tunable passively Q-switched Yb-doped fiber laser. High-quality Sb₂Te₃ crystals were synthesized by the flux zone method. The Sb₂Te₃ SA with fewer layers was further prepared via a modified mechanical exfoliation procedure. Meanwhile, stable wavelength-tunable passive Q-switching pulse operation was obtained in a Yb-doped fiber ring cavity based on the Sb₂Te₃ SA, where the central wavelength can be continuously tuned from 1040.89 to 1092.85 nm. Results suggest that Sb₂Te₃ has wideband saturable absorption properties, and that the tunable pulse laser can provide a convenient and simple source for practical applications.

We study the exfoliation of ultrathin ReS₂ nanosheets from the prepared ReS₂ powder and their application to Q-switched Er-doped fiber laser. XRD, Raman, and XPS spectra confirm the successful preparation of the layered ReS₂. SEM images show that the obtained ReS₂ sheets have lateral size below 200 nm. The thickness of the ReS₂ nanosheets is smaller than 5 nm according to the AFM results. ReS₂/PVA film is applied as a saturable absorber in an Er-doped Q-switched fiber laser, and a minimum pulse duration of 2.4 μs and an output power of 1.25 mW are obtained, indicating the potential application to Q-switched lasers.

We demonstrate the generation of noise-like pulses (NLPs) and soliton rains in a graphene saturable absorber modelocked erbium-doped fiber laser. Typical NLPs are obtained at a proper pump power and in a cavity polarization state. The soliton rain operation with multiple solitons can be achieved by finely adjusting the cavity polarization state. In addition, distinctive multi-soliton interactions are observed and investigated, including the fundamental mode-locking and multiple pulses. The experimental results can help further understand nonlinear pulse dynamics in ultrafast optics.

Developing new saturable absorbers for use in the mid-infrared region has practical significance for short-pulsed lasers and related scientific and industrial applications. The performance of gold nanorods (GNRs) as saturable absorbers at novel mid-infrared wavelengths needs to be evaluated even though these benefit from ultrafast nonlinear responses and broadband saturable absorption. Passive Q-switching of an LD-pumped 2.3 μm Tm:YLF laser using GNRs was successfully realized in this study. Pulses with an 843 ns pulse width and a 6.67 kHz repetition rate were achieved using this Q-switched laser. Results showed that GNRs provide promising passive Q-switches for 2.3 μm Tm-doped lasers.

We built a Tm:Ho co-doped fiber laser using a Ti₃C₂ MXene material as a saturable absorber (SA). The formation of vector solitons (VSs) and noise-like pulses (NLPs) was observed. The SA was prepared by dripping a Ti3C2 solution on a side-polished D-shaped fiber and then naturally vaporized. The VS is characterized by two coexisting sets of Kelly sidebands. By modulating the polarization controller in the fiber laser, NLPs with about 3.3 nm bandwidth can be switched from the VS. To the best of our knowledge, this is the first time that VSs have been generated in a fiber laser using a Ti₃C₂ MXene material as the SA.

Indium selenide (InSe) is a typical layered metal-chalcogenide semiconductor that has potential for developing ultrafast optoelectronic devices. In this work, InSe-polyvinyl alcohol (InSe-PVA) film is employed as saturable absorber and prepared by mixing InSe nanosheets solution and polyvinyl alcohol solution. The nonlinear absorption properties of the InSe saturable absorber (InSe-SA) are investigated, showing that the nonsaturable absorption and modulation depth are 37.5% and 9.55%, respectively. Traditional soliton lasers are generated in erbium-doped fiber (EDF) laser-employed InSe as a mode-locker. The central wavelength and pulse duration of the traditional soliton pulse are 1568.73 nm and 2.06 ps, respectively, under a repetition rate of 1.731 MHz. The maximum average output power is 16.4 mW at the pump power of 413 mW. To the best of our knowledge, this is the first demonstration of a traditional soliton pulse with InSe as a mode-locker. The experimental results further demonstrate that InSe is an outstanding nonlinear absorption material in ultrafast fiber laser.

We demonstrate a graphene-metasurface structure for tunable wide-incident-angle terahertz wave absorption, which involves depositing planar arrays of Omega-shaped graphene patterns on a silicon dioxide substrate. We also discuss how the graphene Fermi-level layer and various substrates affect the absorption characteristics. The absorption of the proposed terahertz absorber is above 80% at an incident angle of 0°–60° in frequencies ranging from 0.82 to 2.0 THz. Our results will be very beneficial in the application of terahertz wave communications and biomedical imaging/sensing systems.

Script is the structured knowledge representation of prototypical real-life event sequences. Learning the commonsense knowledge inside the script can be helpful for machines in understanding natural language and drawing commonsensible inferences. Script learning is an interesting and promising research direction, in which a trained script learning system can process narrative texts to capture script knowledge and draw inferences. However, there are currently no survey articles on script learning, so we are providing this comprehensive survey to deeply investigate the standard framework and the major research topics on script learning. This research field contains three main topics: event representations, script learning models, and evaluation approaches. For each topic, we systematically summarize and categorize the existing script learning systems, and carefully analyze and compare the advantages and disadvantages of the representative systems. We also discuss the current state of the research and possible future directions.

Ubiquitous power Internet of Things (IoT) is a smart service system oriented to all aspects of the power system, and has the characteristics of universal interconnection, human-computer interaction, comprehensive state perception, efficient information processing, and other convenient and flexible applications. It has become a hot topic in the field of IoT. We summarize some existing research work on the IoT and edge computing framework. Because it is difficult to meet the requirements of ubiquitous power IoT for edge computing in terms of real time, security, reliability, and business function adaptation using the general edge computing framework software, we propose a trusted edge computing framework, named “EdgeKeeper,” adapting to the ubiquitous power IoT. Several key technologies such as security and trust, quality of service guarantee, application management, and cloud-edge collaboration are desired to meet the needs of the edge computing framework. Experiments comprehensively evaluate EdgeKeeper from the aspects of function, performance, and security. Comparison results show that EdgeKeeper is the most suitable edge computing framework for the electricity IoT. Finally, future directions for research are proposed.

Traditional diagnosis of attention deficit hyperactivity disorder (ADHD) in children is primarily through a questionnaire filled out by parents/teachers and clinical observations by doctors. It is inefficient and heavily depends on the doctor’s level of experience. In this paper, we integrate artificial intelligence (AI) technology into a software-hardware coordinated system to make ADHD diagnosis more efficient. Together with the intelligent analysis module, the camera group will collect the eye focus, facial expression, 3D body posture, and other children’s information during the completion of the functional test. Then, a multi-modal deep learning model is proposed to classify abnormal behavior fragments of children from the captured videos. In combination with other system modules, standardized diagnostic reports can be automatically generated, including test results, abnormal behavior analysis, diagnostic aid conclusions, and treatment recommendations. This system has participated in clinical diagnosis in Department of Psychology, The Children’s Hospital, Zhejiang University School of Medicine, and has been accepted and praised by doctors and patients.

With technological advancements, weapon system development has become increasingly complex and costly. Using modeling and simulation (M&S) technology in the conceptual design stage is effective in reducing the development time and cost of weapons. One way to reduce the complexity and trial-and-error associated with weapon development using M&S technology is to develop combat scenarios to review the functions assigned to new weapons. Although the M&S technology is applicable, it is difficult to analyze how effectively the weapons are functioning, because of the dynamic features inherent in combat scenario modeling, which considers interrelations among different weapon entities. To support review of weapon functions including these characteristics, this study develops a process-based modeling (PBM) method to model the interactions between weapons in the combat scenario. This method includes the following three steps: (1) construct virtual models by converting the weapons and the weapon functions into their corresponding components; (2) generate the combat process from the combat scenario, which is derived from the interrelations among weapons under consideration using reasoning rules; (3) develop a process-based model that describes weapon functions by combining the combat process with virtual models. Then, a PBM system based on this method is implemented. The case study executed on this system shows that it is useful in deriving process-based models from various combat scenarios, analyzing weapon functions using the derived models, and reducing weapon development issues in the conceptual design stage.