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Smart systems engineering contributing to an intelligent carbon-neutral future: opportunities, challenges, and prospects

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Frontiers of Chemical Science and Engineering 2022年第6期16卷 1023-1029页

作者： Xiaonan Wang Jie Li Yingzhe Zheng Jiali Li Department of Chemical Engineering Tsinghua UniversityBeijing 100084China Department of Chemical&Biomolecular Engineering Faculty of EngineeringNational University of SingaporeSingapore 117585Singapore

This communication paper provides an overview of multi-scale smart systems engineering(SSE)approaches and their applications in crucial domains including materials discovery,intelligent manufacturing,and environmental management.A major focus of this interdisciplinary field is on the design,operation and management of multi-scale systems with enhanced economic and environmental *** emergence of big data analytics,internet of things,machine learning,and general artificial intelligence could revolutionize next-generation research,industry and society.A detailed discussion is provided herein on opportunities,challenges,and future directions of SSE in response to the pressing carbon-neutrality targets.

关键词： machine learning modeling material industrial applications environment

Heat conduction of multilayer nanostructures with consideration of coherent and incoherent phonon transport

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Nano research 2022年第10期15卷 9492-9497页

作者： Bin Liu Yangyu Guo Vladimir I.Khvesyuk Alexander A.Barinov Moran Wang Department of Thermophysics Bauman Moscow State Technical UniversityMoscow 105005Russia Institut Lumière Matière UniversitéClaude Bernard Lyon 1-CNRSUniversitéde LyonVilleurbanne 69622France Key Laboratory for Thermal Science and Power Engineering of Ministry of Education and Center for Flexible Electronics Technology Tsinghua UniversityBeijing 100084China

We report a theoretical investigation of coherent-to-incoherent heat conduction in multilayer *** the coherent regime where the phonon motion is quasi-harmonic,the elastic continuum model gives accurate cross-plane thermal conductivity predictions of upper limits and demonstrates that the coherent transport is the result of the interplay between intrinsic wave *** the temperature or system size increases,the phonon dephasing scattering results in the deviation of thermal conductivity from the coherent-limit *** further introducing the incoherence of phonons,we reproduce the classical minimum thermal conductivity,indicating the feasibility of extending the pure wave model into the wave-particle crossing regime.

关键词： GaAs/AlAs superlattices thermal conductivity coherent and incoherent phonon transport continuum model

Experimental Investigation of Wavelength-Tunable All-Normal-Dispersion Yb-Doped Mode-Locked Fiber Lasers:Compression and Amplification

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Chinese Physics Letters 2015年第2期32卷 63-65页

作者：肖晓晟华弋 State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua University

Wavelength-tunable ultrashort pulse source with high energy is highly desired for a lot of applications. The wavelength-tunable all-normal-dispersion （ANDi） mode-locked fiber laser, which can be compressed easily and amplified by an all-fiber structure, is a promising seed of such a source with compact structures. The pulse compression and amplification at different center wavelengths （from 1026 to 1058nm） of the tunable ANDi Yb- doped mode-locked fiber lasers that we previously proposed are experimentally investigated in this work. It is found that, for different wavelengths, the duration and chirp of the direct output pulse from the oscillator vary considerably, however, the duration of compressed pulse fluctuates less. For the amplification process, due to the unf/at gain spectrum of Yb-doped fiber, the gain at a short wavelength is larger than that at a long wavelength. Consequently, the trends of spectrum distortions induced by the amplification process are different for different wavelengths. These results and analyses will be helpful for the design of a high-energy and wavelength-tunable ultrashort pulse source based on an ANDi seed.

关键词： length In Yb Experimental Investigation of Wavelength-Tunable All-Normal-Dispersion Yb-Doped Mode-Locked Fiber Lasers:Compression and Amplification

Post-Cloud Computing Paradigms： A Survey and Comparison

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tsinghua Science and Technology 2017年第6期22卷 714-732页

作者： Yuezhi Zhou Di Zhang Naixue Xiong Department of Computer Science and Technology Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China Department Mathematics and Computer Science Northeastern State University Tahlequah OK 74464 USA.

With the rapid development of pervasive intelligent devices and ubiquitous network technologies, new network applications are emerging, such as the Internet of Things, smart cities, smart grids, virtual/augmented reality, and unmanned vehicles. Cloud computing, which is characterized by centralized computation and storage,is having difficulty meeting the needs of these developing technologies and applications. In recent years, a variety of network computing paradigms, such as fog computing, mobile edge computing, and dew computing, have been proposed by the industrial and academic communities. Although they employ different terminologies, their basic concept is to extend cloud computing and move the computing infrastructure from remote data centers to edge routers, base stations, and local servers located closer to users, thereby overcoming the bottlenecks experienced by cloud computing and providing better performance and user experience. In this paper, we systematically summarize and analyze the post-cloud computing paradigms that have been proposed in recent years. First, we summarize the main bottlenecks of technology and application that cloud computing encounters. Next, we analyze and summarize several post-cloud computing paradigms, including fog computing, mobile edge computing, and dew ***, we discuss the development opportunities of post-cloud computing via several examples. Finally, we note the future development prospects of post-cloud computing.

关键词： cloud computing fog computing edge computing mobile edge computing dew computing

A Sample-Efficient Actor-Critic Algorithm for Recommendation Diversification

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Chinese Journal of Electronics 2020年第1期29卷 89-96页

作者： LI Shuang YAN Yanghui REN Ju ZHOU Yuezhi ZHANG Yaoxue Department of Computer Science and Technology Tsinghua University

Diversifying recommendation results gains benefits from satisfying user’s existing interests as well as exploring novel information needs. Recently proposed Monte-Carlo based reinforcement learning method suffers from sample inefficiency, large variance, and even failing to perform well in large action space. We propose a novel actor-critic reinforcement learning algorithm for recommendation diversification in order to solve the above mentioned problems. The actor acts as the ranking policy, while the introduced critic predicts the expected future rewards of each candidate action. The critic target is updated by full Bellman equation and the actor network is optimized using expected gradient in the whole action space. To further stabilize and improve the performance, we also add policy-filtered critic supervision loss. Experiments on MovieLens dataset well demonstrate the effectiveness of our approach over multiple competitive methods.

关键词： Recommender system Diversity Reinforcement learning Actor-critic

Non-convex optimization for inverse problem solving in computer-generated holography

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Light(Science & Applications) 2024年第8期13卷 1464-1486页

作者： Xiaomeng Sui Zehao He Daping Chu Liangcai Cao Department of Precision Instruments Tsinghua UniversityBeijing 100084China Department of Engineering Centre for Photonic Devices and SensorsUniversity of Cambridge9 JJ Thomson AvenueCambridge CB30FAUK Cambridge university Nanjing Centre of Technology and Innovation 23 Rongyue RoadJiangbei New AreaNanjing 210000China

Computer-generated holography is a promising technique that modulates user-defined wavefronts with digital *** appropriate holograms with faithful reconstructions is not only a problem closely related to the fundamental basis of holography but also a long-standing challenge for researchers in general fields of *** the exact solution of a desired hologram to reconstruct an accurate target object constitutes an ill-posed inverse *** general practice of single-diffraction computation for synthesizing holograms can only provide an approximate answer,which is subject to limitations in numerical *** non-convex optimization algorithms are thus designed to seek an optimal solution by introducing different constraints,frameworks,and ***,we overview the optimization algorithms applied to computer-generated holography,incorporating principles of hologram synthesis based on alternative projections and gradient descent *** is aimed to provide an underlying basis for optimized hologram generation,as well as insights into the cuttingedge developments of this rapidly evolving field for potential applications in virtual reality,augmented reality,head-up display,data encryption,laser fabrication,and metasurface design.

关键词： optimization convex inverse

Neurogenic differentiation of human umbilical cord mesenchymal stem cells on aligned electrospun polypyrrole/ polylactide composite nanofibers with electrical stimulation

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Frontiers of Materials Science 2016年第3期10卷 260-269页

作者： Junfeng ZHOU Liang CHENG Xiaodan SUN Xiumei WANG ShouhongJIN Junxiang LI Qiong WU Key Laboratory of Advanced Materials of Ministry of Education of China School of Materials Science and Engineering Tsinghua University Beijing 100084 China School of Life Sciences Tsinghua University Beijing 100084 China

Adult central nervous system （CNS） tissue has a limited capacity to recover after trauma or disease. Recent medical cell therapy using polymeric biomaterial- loaded stem cells with the capability of differentiation to specific neural population has directed focuses toward the recovery of CNS. Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal cells. Here we report on the fabrication of an electrospun polypyrrole/polylactide composite nanofiber film that direct or determine the fate of mesenchymal stem cells （MSCs）, via combination of aligned surface topography, and electrical stimulation （ES）. The surface morphology, mechanical properties and electric properties of the film were characterized. Comparing with that on random surface film, expression of neurofilament-lowest and nestin of human umbilical cord mesenchymal stem cells （huMSCs） cultured on film with aligned surface topography and ES were obviously enhanced. These results suggest that aligned topography combining with ES facilitates the neurogenic differentiation of huMSCs and the aligned conductive film can act as a potential nerve scaffold.

关键词： human umbilical cord mesenchymal stem cells neurogenic differentiation conductive composite film electrospun nanofibers electrical stimulation

Unicyclic Graphs of Minimal Spectral Radius

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Acta Mathematica Sinica,English Series 2013年第2期29卷 281-286页

作者： Ling Sheng SHI Department of Mathematical Sciences Tsinghua University

It was conjectured by Li and Feng in 1979 that the unicyclic graph formed by a cycle of order g linking to an endvertex of a path of length k minimizes the spectral radius of all unicyclic graphs of order g ＋ k and girth g. In 1987, Cao proved that this conjecture is true for k ≥ g（g - 2）/8 and false for k = 2 and sufficiently large g. In this note, we show that g 〉12 suffices for the counterexample and give more counterexamples with large girth for any integer k 〉 1.

关键词： Extremal graph Li-Feng's conjecture spectral radius unicyclic

Synthesizing Robot programs with Interactive Tutor Mode

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International Journal of Automation and computing 2019年第4期16卷 462-474页

作者： Hao Li Yu-Ping Wang Tai-Jiang Mu tsinghua National Laboratory for Information Science and Technology(TNList) Department of Computer Science and TechnologyTsinghua University

With the rapid development of the robotic industry, domestic robots have become increasingly popular. As domestic robots are expected to be personal assistants, it is important to develop a natural language-based human-robot interactive system for end-users who do not necessarily have much programming knowledge. To build such a system, we developed an interactive tutoring framework, named " Holert”, which can translate task descriptions in natural language to machine-interpretable logical forms automatically. Compared to previous works, Holert allows users to teach the robot by further explaining their intentions in an interactive tutor mode. Furthermore, Holert introduces a semantic dependency model to enable the robot to " understand” similar task descriptions. We have deployed Holert on an open-source robot platform, Turtlebot 2. Experimental results show that the system accuracy could be significantly improved by 163.9% with the support of the tutor mode. This system is also efficient. Even the longest task session with 10 sentences can be handled within 0.7 s.

关键词： Human-robot interaction semantic parsing program synthesis intelligent robotic systems natural language unders-tanding