A5100398363- Lightning and Electromagnetic Phenomena
- Solid State Laser Technologies
- Fire effects on ecosystems
- Photorefractive and Nonlinear Optics
- Ionosphere and magnetosphere dynamics
- Laser Design and Applications
- Model Reduction and Neural Networks
- Electrical Fault Detection and Protection
- Plant Surface Properties and Treatments
- Meteorological Phenomena and Simulations
- Optical Systems and Laser Technology
- Environmental Changes in China
- China's Ethnic Minorities and Relations
- Plant responses to water stress
- Magnetic properties of thin films
- Advanced Fiber Laser Technologies
- Crystal Structures and Properties
- Physics of Superconductivity and Magnetism
- Heat Transfer and Optimization
- Financial Reporting and Valuation Research
- Bach Studies and Logistics Development
- Emotional Labor in Professions
- Electrostatic Discharge in Electronics
- Heat Transfer Mechanisms
- Atmospheric aerosols and clouds
Nanjing University
2024
Collaborative Innovation Center of Advanced Microstructures
2024
National University of Defense Technology
2023
World Meteorological Organization
2023
Beijing Jiaotong University
2023
Inner Mongolia University of Technology
2022
Huazhong University of Science and Technology
2022
Southern University of Science and Technology
2022
Georgia Institute of Technology
2022
China Meteorological Administration
2016-2020
Abstract Using a high‐speed video camera operated at 150,000 frames per second, we have documented the upward propagation of an initial positive leader from 325 m meteorological tower in Beijing. The stepwise development was clearly revealed during its self‐sustained toward cloud base, providing first optical evidence for stepping processes leader. developed with definitive intermittent pauses and re‐establishment abrupt jump top. Obvious brush‐like corona zone emitting outward top...
A fundamental question in lightning flash concerns why the discharge channel propagates a zig-zag manner and produces extensive branches. Here we report optical observation of two negative cloud-to-ground discharges with very high temporal resolution 180,000 frames per second, which shows detail dependence branching tortuous behavior on stepping process leader development. It is found that clustered space leaders formed parallel ahead tip during an individual step process. The due to...
Abstract In 2009 and 2010, a multistation network of fast slow antennas was installed on the edge relatively high latitude forest region in Da Hinggan Ling (50.4°N, 124.1°E) northeastern China. The documented 185 positive cloud‐to‐ground (CG) flashes containing 196 return strokes were analyzed paper. It found that 71.89% CG contained continuing current. average duration current short with an arithmetic mean value 33.29 ms geometric 16.74 ms; only one lasted longer than 150 ms, probably...
Abstract A negative lightning flash with 16 leader‐return stroke sequences, triggered in the summer of 2013 using classical rocket‐and‐wire triggering technique, was examined simultaneous two‐dimensional (2D) imaging very high‐frequency (VHF) radiation sources, channel‐base current measurement, broadband electric field waveforms and high‐speed video images. total 28.0 C charge transferred to ground during whole flash, initial stage 4.9 C, which is weakest among flashes at SHandong...
Abstract Propagation characteristics of a negative cloud‐to‐ground lightning with four leader‐return stroke sequences exhibiting ground terminations, referred to as multiple termination flash, are analyzed using two‐dimensional mapping system radiation sources in VHF band along broadband electric field change records. The stepped leader‐stroke were produced from two different branches the preliminary breakdown process inside cloud, and time intervals between each adjacent 82.9 ms, 81.4 152.2...
We report a nanosecond (ns) 165 nm deep-ultraviolet (DUV) laser with maximum average power of 2.14 mW by eighth-harmonic generation (EHG) homemade ns 1319 Nd:YAG laser. The EHG was performed cascaded second-harmonic (SHG) through successive stages two LiB3O5 crystals and one KBe2BO3F2 crystal. generated radiation at is the shortest DUV wavelength ever SHG method highest all solid state lasers below 170 to our knowledge. Such great interest for photoemission spectroscopy Raman spectroscopy.
Since their discovery, the infinite-layer nickelates have been regarded as an appealing system for gaining deeper insights into high-temperature superconductivity (HTSC). However, synthesis of superconducting samples has proven to be challenging. Here, ultrahigh vacuum (UHV)
Abstract The grounding process and the associated leader behavior were analyzed by using high‐speed video record time‐correlated electric field change for 37 natural negative cloud‐to‐ground flashes. Weak luminous grounded channel was recognized below downward tip in frame preceding return stroke, which is inferred as upward connecting considering physical of lightning attachment, though not directly confirmed sequential frames. For stepped leader‐first strokes, leaders tend to be induced...
Partial differential equations (PDEs) are an essential computational kernel in physics and engineering. With the advance of deep learning, physics-informed neural networks (PINNs), as a mesh-free method, have shown great potential for fast PDE solving various applications. To address issue low accuracy convergence problems existing PINNs, we propose self-training network, ST-PINN. Specifically, ST-PINN introduces pseudo label based self-learning algorithm during training. It employs...
Sodium laser guide star (LGS) system has become one of the critical components in modern astronomical adaptive optics (AOS), especially for next-generation extremely large telescopes, such as Thirty Meter Telescope and European Extremely Large Telescope. Since wavefront detection performance AOS is directly related to brightness LGS, it important maximize its photon generation efficiency by all means. D2b line repumping a technique that can greatly increase returned photons either sodium...
Since their discovery, the infinite-layer nickelates have been regarded as an appealing system for gaining deeper insights into high temperature superconductivity (HTSC). However, synthesis of superconducting samples has proved to be challenging. Here, we develop ultrahigh vacuum (UHV) ${\mathrm{\textit{in situ}}}$ reduction method using atomic hydrogen reducing agent and apply it in lanthanum nickelate system. The parameters, including (${\mathrm{\textit{T}_{R}}}$) pressure...
We demonstrate a high-power 556nm yellow-green laser generated by intracavity frequency doubling of diode side-pumped Nd:YAG at 1112nm. A symmetrical L-shaped flat-flat cavity was employed to implement efficient operation the low-gain 1112nm transition and achieve good power scalability. The coatings mirrors were carefully designed optimize performance laser, 92W continuous wave output achieved when pumping diodes reached 960W. By fundamental in lithium triborate crystal, maximum...
Lightning information indicates the intensity and development of severe convection. The characteristics lightning activity charge structure a squall line over Beijing on 13 June 2010 are analyzed by using SAFIR3000 detection data, Doppler weather radar precipitation data. Results show that radiation sources major part in convective leading region with high reflectivity front line, number gradually increases back stratiform only at dissipating stage. correlation coefficient between total is...
Abstract At about 22:43:30 BJT (Beijing Time = UTC + 8) on 13 August 2016, two amateur astronomers in Shikengkong, Guangdong province, and Jiahe County, Hunan respectively, fortuitously captured a gigantic jet (GJ) event simultaneously, the GJ exact location could be triangulated. The parent thunderstorm was very humid environment (Precipitable Water [PWAT] excess of 60 mm), featuring high convective available potential energy (CAPE 2,428 J/kg). occurred region with coldest cloud top...
Computational fluid dynamics (CFD) plays a critical role in many scientific and engineering applications, with aerodynamic design optimization being primary area of interest. Recently, there has been much interest using artificial intelligence approaches to accelerate this process. One promising method is the graph convolutional neural network (GCN), deep learning based on networks (ANNs). In paper, we propose novel GCN-based acceleration framework, framework. The framework significantly...
Abstract We examine the low‐frequency (LF) magnetic pulses recorded for positive leader in two natural lightning flashes as on high‐speed video camera. The captured both cases propagated a stepwise manner at least over several milliseconds according to concurrent sequence of LF pulses. By comparing with previous studies leaders under different situations, average inter‐pulse intervals (11.7 and 20.3 μs, respectively) obtained our are shorter than that upward rocket‐triggered (typically...
We demonstrate a high-power UV 278 nm laser by fourth-harmonic generation (FHG) of 1112 Nd:YAG in nonlinear optical (NLO) crystal CsB3O5 (CBO) for the first time, to our best knowledge. A 30 W level diode-pumped Q-switched at with beam quality factor M2=1.2 was used as fundamental light source pulse width 500 ns. With an LiB3O5 crystal, frequency-doubled 556 average output power 13.5 W. It then frequency doubled again CBO obtain FHG nm. The maximum is up 1.5 results demonstrated that...
We demonstrate a multiwavelength laser in the green-yellow region by means of diode-pumped neodymium-doped yttrium aluminum garnet laser. This system combines homemade 1074 nm and 1112 dual-wavelength with extracavity second harmonic generation (SHG) or sum-frequency lithium triborate crystal to generate visible output at any one three wavelengths, 537 nm, 546 556 simple temperature tuning, which has an important application detecting carbon monoxide. The maximum average power wavelengths...