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Journal of Bionic Engineering 2022年第5期19卷 1460-1471页

作者： Lei TIAN Liuchao Qiu College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China

Wetting properties are significant for a hydrophobic surface and normally characterized by the equilibrium contact angle.In this manuscript,a mesoscopic method based on multiphase multiple-relaxation-time Lattice Boltzmann method has been presented and applied to simulate the contact angle at three-phase interfaces of a solid surface with micro-pillar structure.The influence of different parameters including pillar height,pillar width,inter-pillar spacing,intrinsic contact angle and the volume of the liquid drop on the equilibrium contact angle has been comprehensively investigated.The effect of geometry parameters of the micro-pillar structure on the wetting transition from Cassie–Baxter state to Wenzel state has also been studied.The results indicate that when the inter-pillar spacing is less than a certain value or the pillar height is greater than a certain value,the contact form between the droplet and the surface satisfies the Cassie–Baxter state.When the contact form satisfies the Cassie–Baxter state,the contact angle gradually increases with the increase of the inter-pillar spacing;the contact angle does not change significantly with the pillar height;the contact angle gradually decreases and approaches the intrinsic contact angle with the pillar width increases.Moreover,the contact angle increases with the increase of the intrinsic contact angle,and the contact angle is not sensitive to the change of droplet volume when the droplet volume is between 0.5 and10μl.

关键词： Bioinspired hydrophobic surface Wettability Cassie-Baxter state Wenzel state Lattice Boltzmann method Mesoscale simulation

Deep learning augmented microscopy: a faster, wider view, higher resolution autofluorescenceharmonic microscopy

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Light(Science & Applications) 2022年第5期11卷 746-747页

作者： Lei TIAN Department of Electrical and Computer Engineering Boston UniversityBostonMA 02215USA Department of Biomedical Engineering Boston UniversityBostonMA 02215USA

Deep learning enables bypassing the tradeoffs between imaging speed,field of view,and spatial resolution in autofluorescence-harmonic microscopy.

关键词： harmonic Deep faster

Computer-free computational imaging: optical computing for seeing through random media

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Light(Science & Applications) 2022年第3期11卷 4-5页

作者： Yunzhe Li Lei TIAN Department of Electrical and Computer Engineering Boston UniversityBostonMA02215USA Department of Biomedical Engineering Boston UniversityBostonMA02215USA

Diffractive Deep Neural Network enables computer-free,all-optical“computational imaging”for seeing through unknown random diffusers at the speed of light.

关键词： random free enable

Direct observation of spreading precursor liquids in a corner

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National Science Review 2023年第7期10卷 196-202页

作者： Weining Miao Shihao tian Quanzi Yuan Ye tian lei Jiang Key Laboratory of Bioinspired Smart Interfacial Science Technical Institute of Physics and Chemistry Chinese Academy of Sciences School of Future Technology University of Chinese Academy of Sciences State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences School of Engineering Science University of Chinese Academy of Sciences

Precursor liquid is a nanoscale liquid creeping ahead of the macroscopic edge of spreading liquids,whose behaviors tightly correlate with the three-phase reaction efficiency and patterning accuracy.However,the important spatial-temporal characteristic of the precursor liquid still remains obscure because its real-time spreading process has not been directly observed.Here,we report that the spreading ionic liquid precursors in a silicon corner can be directly captured on video using in situ scanning electron microscopy.In situ spreading videos show that the precursor liquid spreads linearly over time(ΔL～ΔT) rather than obeying the classic Lucas-Washburn law(l～t1/2) and possesses a characteristic width of ～250-310 nm.Theoretical analyses and molecular dynamics simulations demonstrate that the unique behaviors of precursor liquids originate from the competing effect of van der Waals force and surface energy.These findings provide avenues for directly observing liquid/solid interfacial phenomena on a microscopic level.

关键词： precursor liquid spreading spatial–temporal characteristic direct observation corner ionic liquids

Total synthesis of lissodendoric acid A by[4+2]cycloaddition of transient cyclic allene

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Chinese Journal of Natural Medicines 2023年第3期21卷 161-162页

作者： tian Hongchang ZHANG lei Department of Pharmaceutical Botany School of PharmacyNaval Medical UniversityShanghai 200433China

Lissodendoric acid A is a member of manzamine alkaloid family[1],which is a popular target for total synthesis due to its complex structure and promising biological activity[2].Lissodendoric acid A was isolated from the marine sponge Lissodendoryx florida in 2017 by Stonik’s group.Related research has demonstrated that this natural product exerted therapeutic effect on a Parkinson’s disease model containing Neuro 2a cells and somewhat increased the survival of these cells upon treatment with dopamine[3].The core skeleton of lissodendoric acid A features an azadecalin scaffold containing a conjugated diene,a carboxylic acid substituent and two stereocenters,which poses a forbidding challenge on total synthesis.Since the 1960s,the small ring structure bearing allene has been known to chemists as an unconventional transient intermediate[4,5],whose unique chemical structure makes it highly reactive,allowing events such as cycloaddition,nucleophilic addition or metal catalysis to occur.However,the application of cyclic allenes in total synthesis of complex natural products has rarely been reported compared with their close relatives,such as arynes and strained cyclic alkynes[6].

关键词： synthesis transient sponge

Design and Mechanical Characterization of an S-Based TPMS Hollow Isotropic Cellular Structure

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Computer Modeling in Engineering & Sciences 2022年第5期131卷 695-713页

作者： Junjian Fu Pengfei Sun Yixian Du Lei TIAN Qihua tian Xiangman Zhou College of Mechanical and Power Engineering China Three Gorges UniversityYichang443002China Hubei Key Laboratory of Hydroelectric Machinery Design&Maintenance Yichang443002China

Cellular structures are regarded as excellent candidates for lightweight-design,load-bearing,and energy-absorbing applications.In this paper,a novel S-based TPMS hollow isotropic cellular structure is proposed with both superior load-bearing and energy-absorbing performances.The hollow cellular structure is designed with Boolean operation based on the Fischer-Koch(S)implicit triply periodic minimal surfaces(TPMS)with different level parameters.The anisotropy and effective elasticity properties of cellular structures are evaluated with the numerical homogenization method.The finite element method is further conducted to analyze the static mechanical performance of hollow cellular structure considering the size effect.The compression experiments are finally carried out to reveal the compression properties and energy-absorption characteristics.Numerical results of the Zener ratio proved that the S-based hollow cellular structure tends to be isotropic,even better than the sheet-based Gyroid TPMS.Compared with the solid counterpart,the S-based hollow cellular structure has a higher elastic modulus,better load-bearing and energy absorption characteristics.

关键词： Hollow cellular structure triply periodic minimal surfaces isotropic property energy absorption load-bearing

Adaptive 3D descattering with a dynamic synthesis network

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Light(Science & Applications) 2022年第5期11卷 766-786页

作者： Waleed Tahir Hao Wang Lei TIAN Department of Electrical and Computer Engineering Boston UniversityBostonMA 02215USA Department of Biomedical Engineering Boston UniversityBostonMA 02215USA

Deep learning has been broadly applied to imaging in scattering applications.A common framework is to train a descattering network for image recovery by removing scattering artifacts.To achieve the best results on a broad spectrum of scattering conditions,individual“expert”networks need to be trained for each condition.However,the expert’s performance sharply degrades when the testing condition differs from the training.An alternative brute-force approach is to train a“generalist”network using data from diverse scattering conditions.It generally requires a larger network to encapsulate the diversity in the data and a sufficiently large training set to avoid overfitting.Here,we propose an adaptive learning framework,termed dynamic synthesis network(DSN),which dynamically adjusts the model weights and adapts to different scattering conditions.The adaptability is achieved by a novel“mixture of experts”architecture that enables dynamically synthesizing a network by blending multiple experts using a gating network.We demonstrate the DSN in holographic 3D particle imaging for a variety of scattering conditions.We show in simulation that our DSN provides generalization across a continuum of scattering conditions.In addition,we show that by training the DSN entirely on simulated data,the network can generalize to experiments and achieve robust 3D descattering.We expect the same concept can find many other applications,such as denoising and imaging in scattering media.Broadly,our dynamic synthesis framework opens up a new paradigm for designing highly adaptive deep learning and computational imaging techniques.

关键词： network scattering synthesis

Astudy of uplink and downlink channel spatial characteristics in an urban micro scenario at 28GHz

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Frontiers of Information Technology & Electronic Engineering 2021年第4期22卷 488-502页

作者： Tao JIANG Jianhua ZHANG Pan TANG Lei TIAN State Key Lab of Networking and Switching Technology Beijing University of Posts and TelecommunicationsBeijing 100876China

This paper presents an empirical study of the uplink and downlink azimuth angle of arrival(AoA)in an urban micro(UMi)scenario at 28 GHz.At present,most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity.Although the channel correlation coefficient of the uplink and downlink can be as high as 0.8,this does not mean that they are the same.Only a real uplink measurement can accurately describe its channel conditions,and this is what this study does.A receiver equipped with a rotatable horn antenna is mounted at the base station and the user terminal,respectively,in simulating the uplink and downlink.To improve the angular resolution,we extract the multipath components(MPCs)using the space-alternating generalized expectation-maximization algorithm.Also,a spatial lobe approach is used to cluster the MPCs in the power angular spectrum.By matching MPCs with objects in the environment,we find that direct propagation and first-order reflections are dominant in line-of-sight and non-line-of-sight cases.By comparing our measurement with those in standard channel models,we verify that the AoA of clusters follows a Gaussian distribution in the uplink and downlink.In addition,a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.

关键词： Channel measurements Millimeter-wave(mmWave) Uplink Downlink Azimuth angle of arrival

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Feedbacks between vegetation restoration and local precipitation over the Loess Plateau in China

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Science China Earth Sciences 2021年第6期64卷 920-931页

作者： Baoqing ZHANG Lei TIAN Xining ZHAO Pute WU Key Laboratory of Western China’s Environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou730000China Institute of Green Development for the Yellow River Drainage Basin Lanzhou UniversityLanzhou730000China Institute of Soil and Water Conservation Northwest A&F UniversityYangling712100China

The implementation of large-scale vegetation restoration over the Chinese Loess Plateau has achieved clear improvements in vegetation fraction,as evidenced by large areas of slopes and plains being restored to grassland or forest.However,such large-scale vegetation restoration has altered land-atmosphere exchanges of water and energy,as the land surface characteristics have changed.These variations could affect regional climate,especially local precipitation.Quantitatively evaluating this feedback is an important scientific question in hydrometeorology.This study constructs a coupled land-atmosphere model incorporating vegetation dynamics,and analyzes the spatio-temporal changes of different land use types and land surface parameters over the Loess Plateau.By considering the impacts of vegetation restoration on the water-energy cycle and on land-atmosphere interactions,we quantified the feedback effect of vegetation restoration on local precipitation across the Loess Plateau,and discussed the important underlying processes.To achieve a quantitative evaluation,we designed two simulation experiments,comprising a real scenario with vegetation restoration and a hypothetical scenario without vegetation restoration.These enabled a comparison and analysis of the net impact of vegetation restoration on local precipitation.The results show that vegetation restoration had a positive effect on local precipitation over the Loess Plateau.Observations show that precipitation on the Loess Plateau increased significantly,at a rate of 7.84 mm yr^(-2),from 2000 to 2015.The simulations show that the contribution of large-scale vegetation restoration to the precipitation increase was about 37.4%,while external atmospheric circulation changes beyond the Loess Plateau contributed the other 62.6%.The average annual precipitation under the vegetation restoration scenario over the Loess Plateau was 12.4%higher than that under the scenario without vegetation restoration.The above research results have important theoretical and practical s

关键词： Coupled land-atmosphere modeling Vegetation restoration Water balance Hydrometeorology Ecohydrology

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Hybrid neural state machine for neural network

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Science China(Information Sciences) 2021年第3期64卷 136-148页

作者： Lei TIAN Zhenzhi WU Shuang WU Luping SHI Department of Precision Instrument Center for Brain-Inspired Computing Research(CBICR)Beijing Innovation Center for Future Chip Tsinghua University

The integration of computer-science-oriented and neuroscience-oriented approaches is believed to be a promising way for the development of artificial general intelligence(AGI). Recently, a hybrid tianjic chip that integrates both approaches has been reported, providing a general platform to facilitate the research of AGI. The control algorithm for handling various neural networks is the key to this platform; however, it is still primitive. In this work, we propose a hybrid neural state machine(H-NSM) framework that can efficiently cooperate with artificial neural networks and spiking neural networks and control the workflows to accomplish complex tasks. The H-NSM receives input from different types of networks, makes decisions according to the fusing of various information, and sends control signals to the sub-network or actuator. The H-NSM can be trained to adapt to context-aware tasks or sequential tasks, thereby improving system robustness. The training algorithm works correctly even if only 50% of the forced state information is provided. It achieved performance comparable to the optimum algorithm on the Tower of Hanoi task and achieved multiple tasks control on a self-driving bicycle. After only 50 training epochs, the transfer accuracy reaches 100% in the test case. It proves that H-NSM has the potential to advance control logic for hybrid systems, paving the way for designing complex intelligent systems and facilitating the research towards AGI.

关键词： hybrid neural state machine ANNs SNNs supervised learning context-aware task sequential task