In situ TEM revealing the effects of dislocations on lithium-ion migration in transition metal dichalcogenides

The two-dimensional (2D) structure of layered transition metal dichalcogenides (TMDs) provides unusual physical properties [1,2]and chemical reactivity [3,4], which can be influenced by defects such as dislocations [5,6]. For example, dislocations can act as nucleation sites for the onset of deformation when subjected to stress [7].

Singular Sheet Etching of Graphene with Oxygen Plasma

This paper reports a simple and controllable post-synthesis method for engineering the number of graphene layers based on oxygen plasma etching. Singular sheet etching(SSE) of graphene was achieved with the optimum process duration of 38 seconds. As a demonstration of this SSE process, monolayer graphene films were produced from bilayer graphenes. Experimental investigations verified that the oxygen plasma etching removes a single layer graphene sheet in an anisotropic fashion rather than anisotropic mode. In addition,etching via the oxygen plasma at the ground electrodes introduced fewer defects to the bottom graphene layer compared with the conventional oxygen reactive ion etching using the powered electrodes. Such defects can further be reduced with an effective annealing treatment in an argon environment at 900-1000?C. These results demonstrate that our developed SSE method has enabled a microelectronics manufacturing compatible way for single sheet precision subtraction of graphene layers and a potential technique for producing large size graphenes with high yield from multilayer graphite materials.

Recent progress in three-terminal artificial synapses based on 2D materials:from mechanisms to applications

Synapses are essential for the transmission of neural signals.Synaptic plasticity allows for changes in synaptic strength,enabling the brain to learn from experience.With the rapid development of neuromorphic electronics,tremendous efforts have been devoted to designing and fabricating electronic devices that can mimic synapse operating modes.This growing interest in the field will provide unprecedented opportunities for new hardware architectures for artificial intelligence.In this review,we focus on research of three-terminal artificial synapses based on two-dimensional(2D)materials regulated by electrical,optical and mechanical stimulation.In addition,we systematically summarize artificial synapse applications in various sensory systems,including bioplastic bionics,logical transformation,associative learning,image recognition,and multimodal pattern recognition.Finally,the current challenges and future perspectives involving integration,power consumption and functionality are outlined.

In situ atomic-scale observation of size-dependent (de) potassiation and reversible phase transformation in tetragonal FeSe anodes

Potassium-ion batteries(PIBs)are considered promising alternatives to lithium-ion batteries owing to cost-effective potassium resources and a suitable redox potential of-2.93 V(vs.-3.04 V for Li+/Li).However,the exploration of appro-priate electrode materials with the correct size for reversibly accommodating large K+ions presents a significant challenge.In addition,the reaction mecha-nisms and origins of enhanced performance remain elusive.Here,tetragonal FeSe nanoflakes of different sizes are designed to serve as an anode for PIBs,and their live and atomic-scale potassiation/depotassiation mechanisms are revealed for the first time through in situ high-resolution transmission electron micros-copy.We found that FeSe undergoes two distinct structural evolutions,sequen-tially characterized by intercalation and conversion reactions,and the initial intercalation behavior is size-dependent.Apparent expansion induced by the intercalation of K+ions is observed in small-sized FeSe nanoflakes,whereas unexpected cracks are formed along the direction of ionic diffusion in large-sized nanoflakes.The significant stress generation and crack extension originating from the combined effect of mechanical and electrochemical interactions are elucidated by geometric phase analysis and finite-element analysis.Despite the different intercalation behaviors,the formed products of Fe and K_(2)Se after full potassiation can be converted back into the original FeSe phase upon depotassiation.In particular,small-sized nanoflakes exhibit better cycling perfor-mance with well-maintained structural integrity.This article presents the first successful demonstration of atomic-scale visualization that can reveal size-dependent potassiation dynamics.Moreover,it provides valuable guidelines for optimizing the dimensions of electrode materials for advanced PIBs.

Self-sensing intelligent microrobots for noninvasive and wireless monitoring systems

Microrobots have garnered tremendous attention due to their small size,flexible movement,and potential for various in situ treatments.However,functional modification of microrobots has become crucial for their interaction with the environment,except for precise motion control.Here,a novel artificial intelligence(AI)microrobot is designed that can respond to changes in the external environment without an onboard energy supply and transmit signals wirelessly in real time.The AI microrobot can cooperate with external electromagnetic imaging equipment and enhance the local radiofrequency(RF)magnetic field to achieve a large penetration sensing depth and a high spatial resolution.The working ranges are determined by the structure of the sensor circuit,and the corresponding enhancement effect can be modulated by the conductivity and permittivity of the surrounding environment,reaching~560 times at most.Under the control of an external magnetic field,the magnetic tail can actuate the microrobotic agent to move accurately,with great potential to realize in situ monitoring in different places in the human body,almost noninvasively,especially around potential diseases,which is of great significance for early disease discovery and accurate diagnosis.In addition,the compatible fabrication process can produce swarms of functional microrobots.The findings highlight the feasibility of the self-sensing AI microrobots for the development of in situ diagnosis or even treatment according to sensing signals.

Developing the Science Product Algorithm Testbed for Chinese Next-Generation Geostationary Meteorological Satellites：Fengyun-4 Series

Fengyun-4A（FY-4A）, the first of the Chinese next-generation geostationary meteorological satellites, launched in2016, offers several advances over the FY-2： more spectral bands, faster imaging, and infrared hyperspectral measurements. To support the major objective of developing the prototypes of FY-4 science algorithms, two science product algorithm testbeds for imagers and sounders have been developed by the scientists in the FY-4 Algorithm Working Group（AWG）. Both testbeds, written in FORTRAN and C programming languages for Linux or UNIX systems, have been tested successfully by using Intel/g compilers. Some important FY-4 science products, including cloud mask, cloud properties, and temperature profiles, have been retrieved successfully through using a proxy imager, Himawari-8/Advanced Himawari Imager（AHI）, and sounder data, obtained from the Atmospheric Infra Red Sounder, thus demonstrating their robustness. In addition, in early 2016, the FY-4 AWG was developed based on the imager testbed—a near real-time processing system for Himawari-8/AHI data for use by Chinese weather forecasters.Consequently, robust and flexible science product algorithm testbeds have provided essential and productive tools for popularizing FY-4 data and developing substantial improvements in FY-4 products.

The Tibetan Plateau Surface–Atmosphere Coupling System and Its Weather and Climate Effects: The Third Tibetan Plateau Atmospheric Science Experiment

The Tibetan Plateau(TP) is a key area affecting forecasts of weather and climate in China and occurrences of extreme weather and climate events over the world. The China Meteorological Administration, the National Natural Science Foundation of China, and the Chinese Academy of Sciences jointly initiated the Third Tibetan Plateau Atmospheric Science Experiment(TIPEX-Ⅲ) in 2013, with an 8–10-yr implementation plan. Since its preliminary field measurements conducted in 2013, routine automatic sounding systems have been deployed at Shiquanhe, Gaize, and Shenzha stations in western TP, where no routine sounding observations were available previously. The observational networks for soil temperature and soil moisture in the central and western TP have also been established. Meanwhile, the plateau-scale and regional-scale boundary layer observations, cloud–precipitation microphysical observations with multiple radars and aircraft campaigns, and tropospheric–stratospheric air composition observations at multiple sites, were performed. The results so far show that the turbulent heat exchange coefficient and sensible heat flux are remarkably lower than the earlier estimations at grassland, meadow, and bare soil surfaces of the central and western TP. Climatologically, cumulus clouds over the main body of the TP might develop locally instead of originating from the cumulus clouds that propagate northward from South Asia. The TIPEX-Ⅲ observations up to now also reveal diurnal variations, macro-and microphysical characteristics, and water-phase transition mechanisms, of cumulus clouds at Naqu station. Moreover, TIPEX-Ⅲ related studies have proposed a maintenance mechanism responsible for the Asian "atmospheric water tower" and demonstrated the effects of the TP heating anomalies on African, Asian, and North American climates. Additionally, numerical modeling studies show that the Γ distribution of raindrop size is more suitable for depicting the TP raindrop characteristics compared to the M–P distribution, the overestimation of sensible heat flux can be reduced via modifying the heat transfer parameterization over the TP, and considering climatic signals in some key areas of the TP can improve the skill for rainfall forecast in the central and eastern parts of China. Furthermore, the TIPEX-Ⅲ has been promoting the technology in processing surface observations, soundings, and radar observations, improving the quality of satellite retrieved soil moisture and atmospheric water vapor content products as well as high-resolution gauge–radar–satellite merged rainfall products, and facilitating the meteorological monitoring, forecasting, and data sharing operations.

Field validation of the GLASS land surface broadband emissivitydatabase using pseudo-invariant sand dune sites in northern China

The land surface broadband emissivity (LSBE) is a key parameter for estimatingsurface radiation, and there have been many studies of the LSBE at global orlocal scales. However, few studies have validated the surface emissivity databasewith multi-point field measurement data using infrared radiometry, especially inChina. In this study, we focus on the validation of the emissivity product of theglobal land surface satellite (GLASS) LSBE database for northern China for theperiod from 2006 to 2011. Specifically, we have employed an eight-day averaged,gridded emissivity product in the 813.5 mm spectral range produced at a spatialresolution of 1000 m from the Moderate Resolution Imaging Spectrometeralbedo product using a new algorithm. The GLASS LSBE database was validatedover bare surfaces with field measurement data from sand samples collected atmany pseudo-invariant sand dune sites located in western and northwesternChina. By comparing measured emissivity for different land surface types atdifferent sites and different times, it was shown that the results were consistentand that the accuracy of the field measurements was reliable. The results of thevalidation of GLASS LSBE with these field emissivity data showed very goodagreement.