主题报告

Ji Wang
Professor
Ningbo University，China
Speech Title: A Nonlinear Formulation and Analysis of Surface Acoustic Waves in Elastic Solids with the Extended Galerkin Method
Abstract: The nonlinear acoustic waves in piezoelectric resonators are getting attention in product development due to the continuous shrinkage of sizes to a critical limit which causes the effect of electric field is no longer neglectable. Consequently, nonlinear formulation and analysis of wave propagation in such smaller resonators are important in the inception and development future generation of resonators with good properties. By formulating wave propagation and vibrations with a complete set of nonlinear variables and constitutive relations, both kinematic and constitutive nonlinearities are included along with boundary conditions. These differential equations have to be simplified with the newly proposed extended Galerkin method for a simple and efficient solution procedure. Specifically, the weighted integration over both physical domain and the full period of time, in case of a periodic motion, is employed to both equations of motion and boundary conditions, then nonlinear variables including amplitudes and frequency, among others, appear in a set of algebraic equations as a typical nonlinear eigenvalue problem. If it is a static problem, then it is a problem involving the solution of a system of nonlinear equations. In principle, this is equivalent to the utilization of harmonic balance method for the approximation of trigonometric functions, as it is explained in earlier introduction of the extended Galerkin and Rayleigh-Ritz methods. The nonlinear formulation and solution of the Rayleigh wave problem is straightforward with the extended Galerkin method, and numerical results of wave velocity versus deformation for both isotropic and anisotropic materials are obtained and also validated with the finite element analysis. The nonlinear formulation will be applied to the analysis of surface acoustic wave resonators to address the nonlinear effect related to the development of miniaturized products with good properties as a novel technique.

Zhiyuan Zhu
Professor
Southwest University，China
Speech Title: Investigation of self-powered PIN structure for radiation/photoelectric detection
Abstract: PIN detector is widely used for radiation/photoelectric detection. We have fabricated the first 3D integrated silicon PIN device. The  self-powered mechanism of the silicon PIN radiation detector based on triboelectronic nanogenerator is proposed

Vladimir Falko
Professor
National Graphene Institute, University of Manchester
Speech Title: Van der Waals heterostructures of 2D materials for broad-spectrum optoelectronics
Abstract: We discuss the prospects of 2D materials with Γ-point band edges for applications in optoelectronics. The family of such materials includes n-type InSe, GaSe [Phys. Rev. B 94, 245431 (2016); Nature Nanotechnology 12, 223 (2017); ACS Nano 13, 2136 (2019)] and few-layer films of p-type transition metal dichalcogenides (WSe2, WS2, MoSe2, MoS2) [Phys. Rev. B 98, 035411 (2018)]. We show that heterostructures of such materials offer efficient interlayer coupling, promoting layer-indirect optical transitions, which cover a broad range from VIS to IR, depending on the composition of the heterostructures [2D Materials 5, 041009 (2018); Nature Materials 19, 299 (2020)]. Also, we show that multi-component stacks of such materials offer a possibility to build IR light sources, using intersubband transitions in few-layer films [Nature Comm 11, 125 (2020)], excited by the interlayer tunnelling.

Syed Agha Hassnain Mohsan
Faculty Member (Comsats University Islamabad, Quaid e Azam University)
Ocean College, Zhejiang University, China
Speech Title: Optical Wireless Power Transfer and Information Transmission
Abstract: The ground-breaking optical wireless power transmission techniques have gained significant attention from both academia and industrial experts in recent decades. Powering remote systems through laser diodes (LDs) to either operate devices or recharge batteries offers several benefits. Remote LDs can remove burden of carrying extra batteries and can also reduce mission time by removing battery swap-time and charging. Apart from its appealing benefits, laser power transfer (LPT) is still a challenging task due to its low transfer efficiency. This study deals with laser selection, receiver solar cell selection and hazard analysis for optical wireless power transfer (OWPT) systems. In addition, we explain several OWPT techniques including Thing-to-Thing (T2T) OWPT, distributed laser charging (DLC) and adaptive distributed laser charging (ADLC). This study also outlines simultaneous wireless information and power transfer (SLIPT) for Unmanned Aerial Vehicles (UAVs). Finally, we discuss a range of open challenges and counter-measures.

Xukun Yin
Associate professor
Xidian University, China
Speech Title: Photoacoustic Multicomponent SF₆ Decomposition Sensor for an Electric Power System
Abstract: High voltage gas insulated apparatus such as the gas insulated switchgears (GIS) and the gas insulated lines (GIL) have been widely used in power transmission and distribution systems around the world. Due to the high dielectric strength, chemically inactive and environmentally acceptable property, sulfur hexafluoride (SF₆) was widely chosen as the preferred dielectric gas for electrical insulation or interruption purposes in electric power systems. However, GIS/GIL failures occur from time to time from manufacturing defects. Health monitoring of gas insulated apparatus is critical to improve the reliability and to reduce the life cycle cost. Among the various methods for the monitoring, optical sensing developed fast in recent years due to their highly sensitive and anti-electromagnetic interference characteristic. Therefore, a sensitive photoacoustic multicomponent gas sensor for the online monitoring of the SF₆ decompositions in an electric power system was developed. An on-line ppb-level SF₆ decomposition detection gas sensor was developed via a 303 nm solid state laser and two near-IR diode lasers for an electric power system. The minimum detection limits of 440 ppb, 90 ppb and 115 ppb were achieved for CO, H₂S and SO₂ in SF₆ buffer gas by means of a time division multiplexing (TDM) method.

Ping Su
Associate professor
Tsinghua SIGS, Tsinghua University, China
Speech Title: Research on channel modeling and signal detection on ultraviolet communication
Abstract: Ultraviolet communication utilizes ultraviolet light within a ‘sun-blind’ wavelength range of 200~280nm to realize communication. Compared with the traditional RF communication system, the UV communication system has the potential advantages of license free bandwidth, low power consumption and miniaturized transceiver, outstanding transmission power density and strong anti-interference ability. Compared with infrared and visible light communication, ultraviolet communication has the advantages of low background noise, good confidentiality and high data transmission rate. In addition, the ultraviolet communication system has no strict requirements on the positions of the transmitter and receiver, so it can be applied to many communication scenarios, such as line-of-sight communication, non-line-of-sight communication and omni-directional communication.
The research group has done a lot of in-depth research on the channel model, transceiver, modulation, coding and other aspects of UV communication system, and has produced a lot of innovative results, including UV communication single scattering integral model, single scattering approximation model, multiple scattering integral model, Monte-Carlo integral model, omni-directional Monte Carlo simulation model, the impact of jitter effect at the transceiver, UV communication modulation and coding algorithm, single input multiple output nonlinear receiver, etc., which laid a good foundation for the development and application of UV communication.