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Physics-informed deep Koopman operator for Lagrangian dynamic systems

Science China(Information Sciences) 2024年第9期67卷 146-163页

作者： xuefeng wang Yang CAO Shaofeng CHEN Yu KANG Department of Automation University of Science and Technology of China State Key Laboratory of Fire Science University of Science and Technology of China Institute of Advanced Technology University of Science and Technology of China

Accurate mechanical system models are crucial for safe and stable control. Unlike linear systems,Lagrangian systems are highly nonlinear and difficult to optimize because of their unknown system *** research thus used deep neural networks to generate linear models of original systems by mapping nonlinear dynamic systems into a linear space with a Koopman observable function encoder. The controller then relies on the Koopman linear model. However, without physical information constraints, ensuring control consistency between the original nonlinear system and the Koopman system is tough, as the learning process of the Koopman observation function is unsupervised. This paper thus proposes a two-stage learning algorithm that uses structural subnetworks to build a physics-informed network topology to simultaneously learn the Koopman observable functions and the system energy representation. In the Koopman matrix learning session, a quadratic-constrained optimization problem is solved to ensure that the Koopman representation satisfies the energy difference matching hard constraint. The proposed energy-preserving deep Lagrangian Koopman(EPDLK) framework effectively represents the dynamics of the Lagrangian system while ensuring control consistency. The effectiveness of EPDLK is compared with those of various Koopman observable function construction methods in multistep prediction and trajectory tracking tasks. EPDLK achieves better control consistency by guaranteeing energy difference matching, which facilitates the application of the control law generated on the Koopman system directly to the original nonlinear Lagrangian system.

关键词： Koopman operator Lagrangian physics-informed nonlinear model predictive control (MPC)

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Linear and quadratic damping coefficients of a single module of a very large floating structure over variable bathymetry:Physical and numerical free-decay experiments

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Journal of Ocean Engineering and Science 2022年第6期7卷 607-618页

作者： Yiting wang Ziying Tang Lei wang xuefeng wang State Key Laboratory of Ocean Engineering Shanghai Jiao Tong UniversityShanghai 200240China SJTU-Sanya Yazhou Bay Institute of Deepsea Science and Technology Sanya 572024China

The linearity assumption is widely used when acquiring the hydrodynamic coefficients of a floating ***,the linear damping is frequently underestimated,especially for the natural *** investigate the sloping seafloor effects on the damping terms of a single module of a semi-submersible Very Large Floating Structure(VLFS),this paper revisits the conventional formulation and further proposes the direct integration method for obtaining the linear and quadratic damping coefficients from free-decay *** free-decay simulations of the single module over variable bathymetry are carried out by the CFD numerical *** model tests are also implemented to verify and validate against the numerical *** effects of the sloping seafloor,as well as the water depth,on the hydrodynamic coefficients are investigated based on the validated CFD *** numerical and experimental results indicate that the acquisition of the linear and quadratic damping coefficients is sensitive to the data-processing and identification *** the case studied in present paper,the identification errors introduced by the conventional method are 1.5%while they are 0.5%using the direct integration *** quadratic damping coefficient for heave mode decreases about 10.4%when the sloping angle increases from 0 to 6 deg.

关键词： Quadratic damping coefficient Very large floating structure Model tests Numerical simulations

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Single-electron detection utilizing coupled nonlinear microresonators

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Microsystems & Nanoengineering 2020年第1期6卷 327-333页

作者： xuefeng wang Xueyong Wei Dong Pu Ronghua Huan Department of Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang UniversityHangzhou 310027People’s Republic of China State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an 710049People’s Republic of China

Since the discovery of the electron,the accurate detection of electrical charges has been a dream of the scientific *** to some remarkable advantages,micro/nanoelectromechanical system-based resonators have been used to design electrometers with excellent sensitivity and ***,we demonstrate a novel ultrasensitive charge detection method utilizing nonlinear coupling in two micromechanical *** achieve single-electron charge detection with a high resolution up to 0.197±0.056 e=/√Hz Hz p at room *** findings provide a simple strategy for measuring electron charges with extreme accuracy.

关键词： temperature utilizing nonlinear

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Fabrication and luminescence of highly transparent C12A7:Tb^(3+)glass-ceramics via in-situ crystallization from aerodynamic levitation processed glasses

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Journal of Rare Earths 2023年第11期41卷 1696-1702,I0002页

作者： Yaling Zhang Lingcong Fan xuefeng wang Jiansheng Xie Ying Shi School of Materials Science and Engineering Shanghai UniversityShanghai200444China

Rare earth doped 12CaO·7Al_(2)O_(3)(C12A7)glass-ceramics are one of attractive photonic materials due to their high transparency,high luminescent efficiency and eco-friendly nature.A series of C12A7 glasses with different Tb^(3+)doping concentrations was prepared by aerodynamic levitation *** C12A7:Tb glass-ceramics were obtained via in-situ growth from the glasses with the identical chemical composition at 800℃.The microstructure observation demonstrates that the elemental distributions of Ca and Al are homogeneous in the glass-ceramics and the grain size of C12A7 is 4-70 *** in-line transmittance of glass-ceramics reaches as high as 82%at 1500 *** emission spectra of the C12A7:Tb glass-ceramics present characteristic Tb^(3+)emission peaks at 486 nm(^(5)D_(4)→^(7)F_6),541 nm(^(5)D_(4)→^(7)F_(5)),585 nm(^(5)D_(4)→^(7)F_(4))and 621 nm(^(5)D_(4)→^(7)F_(3)).The photolumine scence lifetime of C12A7:0.3%Tb glass-ceramic is 1.9 *** with the emission intensity of the glasses,that of the glass-ceramics increases due to the reducing in concentration of oxygen vacancy associated with network forming(NWF)*** highly transparent C12A7:Tb glass-ceramics may be a promising candidate for green light source in solid state lighting.

关键词： C12A7:Tb Aerodynamic levitation method Glass-ceramics Crystallization Luminescence Rare earths

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SO_(2)-Insertion induced enantioselective oxysulfonylation to access β-chiral sulfones with quaternary carbon stereocenters

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Science China Chemistry 2024年第3期67卷 908-913页

作者： Jun Zhang xuefeng wang Peiqi wang Jiayuan Fang Shaoyu Li Jie Wu School of Pharmaceutical and Chemical Engineering&Institute for Advanced Studies Taizhou UniversityShanghai 200438China Department of Chemistry Fudan UniversityShanghai 200438China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China School of Chemistry and Chemical Engineering Henan Normal UniversityXinxiang 453007China

β-Chiral sulfones are structural motifs widely found in natural products and bioactive molecules, while also serving as important intermediates for the synthesis of valuable chiral scaffolds. In contrast to the rapid growth of sulfur dioxide insertion chemistry over the last decade, enantioselective catalytic variants for accessing β-chiral sulfones, especially those bearing a quaternary carbon stereocenter, remain rare. Herein, we report an enantioselective copper/bisoxazoline catalyzed oxysulfonylation of alkenes to yield isoxazolinyl-containing β-chiral sulfones bearing quaternary carbon stereocenters with moderate to excellent yields and up to 96:4 er. The advantage and irreplaceability of this sulfur dioxide insertion catalytic system have been demonstrated by achieving transformations clearly unavailable with the previously reported sulfonyl chloride system. Additionally,the recoverability of the new-developed bisoxazoline ligand L9 and its reusability without any erosion of the catalytic activity and enantioselectivity further demonstrate the usefulness of the protocol.

关键词： β-chiral sulfones sulfur dioxide insertion oxysulfonylation copper catalysis enantioselectivity

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Spontaneous coal combustion producing carbon dioxide and water

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Mining Science and Technology 2010年第1期20卷 82-87,92页

作者： DENG Cunbao wang Jiren wang xuefeng DENG Hanzhong 1College of Safety Science and Engineering Liaoning Technical University Fuxin 123000 China College of Materials Science and Engineering Liaoning Technical University Fuxin 123000 China

Gas products from the process of coal oxidization and spontaneous combustion have been studied at different temperatures with FTI spectroscopic tests. With temperatures rising to about 30~100 ℃, water and carbon dioxide gas were formed and from about 105~150 ℃, carbon monoxide was produced. Using the DFT B3LYP method with a 6-311G basis set, the reaction system, where spontaneous combustion between coal and oxygen occurs and produces water and monoxide, has been studied, with the geometric configuration for all stagnation points on the potential reaction energy surface optimized. With a frequency analysis and an IRC method, transient formations were tested. Our results indicate that in the reaction of coal oxidization and spontaneous com-bustion producing carbon dioxide and water, oxygen molecules attack carbon atoms of the terminal of the propyl alcohol group on the lateral chain of benzene rings, which causes this propyl alcohol group to produce the acid (-CH2-CH2-COOH) group and water. This acid group continues its break up into carbon dioxide and the (-CH2-CH3) ethyl group. We have come to the conclusion that this water-and-carbon dioxide-production reaction is spontaneous, based on the observation of the energy released by the reaction.

关键词： spontaneous coal combustion infrared spectrum DFT reaction mechanism

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Carbon Nanotube Transistor with Short-Term Memory

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Tsinghua Science and Technology 2016年第4期21卷 442-448页

作者： Changqing Yin Yuxing Li Jiabin wang xuefeng wang Yi Yang Tian-Ling Ren Institute of Microelectronics Tsinghua University Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology Tsinghua University

Short-Term Memory （STM） is a primary capability of the human brain. Humans use STM to remember a small amount of information, like someone＇s phone number, for a short period of time. Usually the duration of STM is less than 1 minute. Synapses, the connections between neurons, are of vital importance to memory in biological brains. For mimicking the memory function of synapses, Carbon Nanotube （CNT） networks based thin- film transistors with Electric Double Layers （EDL） at the dielectric/channel interface were researched in this work. A response characteristic of pre-synaptic potential pulses on the gate electrode of this CNT synaptic transistor was shown remarkably similar to Excitatory Post-Synaptic Current （EPSC） of biological synapses. Also a multi-level modulatable STM of CNT synaptic transistors was investigated. Post-synaptic current was shown with tunable peak values, on-off ratio, and relaxation time.

关键词： carbon nanotube thin-film transistor synapse excitatory postsynaptic current short-term memory

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Centennial-scale monsoon collapses during Marine Isotope Stage(MIS)7e detected in a northern Chinese stalagmite record

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Science China Earth Sciences 2023年第12期66卷 2941-2952页

作者： Wuhui DUAN Ming TAN Lisheng wang xuefeng wang Zhibang MA Linlin CUI Zhengyi XIAO Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of Sciences Beijing 100029China CAS Center for Excellence in Life and Paleoenvironment Beijing 100044China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

Occurrence or absence of centennial-scale climatic variability during Marine Isotope Stage(MIS)7e,the first peak interval of the Penultimate Interglacial,remains ambiguous due to the limited available high-resolved ***,we present a decadal-resolved stalagmiteδ^(18)O record from northern China spanning from 242.3 to 236.8 ka BP,covering *** composite KLSδ^(18)O record,integrating this study with the previous record in the same cave,shows a descending trend from TerminationⅢto MIS7e,which follows the increasing Northern Hemisphere summer insolation(NHSI).This observation further emphasizes the important influence of NHSI on the glacial/interglacial *** are more large-amplitude,millennial-to centennial-scale variability occurring during TerminationⅢcompared with MIS7e,implying that ice-sheet decay potentially plays an important role in climatic *** centennial-scale summer monsoon collapses,peaking at~242.1,~240.8,~239.3 and~238.2 ka BP,are detected in our new record,indicating the pervasiveness of the intra-interglacial climatic *** the lack of solar activity and freshwater outbursts data during MIS7e,it is not possible to conclude about the drivers of the identified abrupt climatic *** the dynamic mechanisms of sub-millennial climatic anomalous during early Holocene,we tentatively propose that slowdown of the meridional overturning circulation caused by freshwater fluxes into North Atlantic and/or attenuated solar irradiance is the potential forcing for the abrupt climate events within ***,attenuated solar irradiance could also result in climatic anomalies through low-latitude processes.

关键词： Northern China Stalagmiteδ~(18)O record Marine Isotope Stage(MIS)7e Centennial-scale monsoon collapses Freshwater and/or solar activity forcings

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Connections between Evaporite Deposition and Glacial Periods since the Middle Pleistocene in Salt Lakes in the Western Qaidam Basin, China

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Acta Geologica Sinica(English Edition) 2022年第5期96卷 1704-1715页

作者： GU Jiani CHEN Andong LIU Jiajun HAN Guang wang xuefeng School of Earth Sciences and Resources China University of Geosciences(Beijing)Beijing 100083China MNR Key Laboratory of Saline Lake Resources and Environments Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China Qinghai Provincial Key Laboratory of Exploration and Research on Salt Lake Resources in the Qaidam Basin Qaidam Integrated Geological Exploration Institute of Qinghai ProvinceGolmudQinghai 816000China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

The Quaternary was the main evaporite deposition period in the Qaidam Basin(QB), but the correlation between the evaporite deposition period and the glacial period is still unclear. In this study, the research objects are primarily evaporite-bearing strata in a 461.58 m-long drill core in the QB. X-ray powder diffraction(XRD) and scanning electron microscopy(SEM) were applied to study the evaporite minerals, U-Th dating being applied to construct the ~(230)Th geochronological framework. Evaporite deposition from Marine Isotope Stage(MIS) 15 to MIS 4 in the borehole was reconstructed via mineralogical and geochronological data. The evaporite minerals are mainly halite(NaCl), mirabilite(Na_(2)SO_(4)·10H_(2)O), thenardite(Na_(2)SO_(4)) and gypsum(CaSO_(4)·2H_(2)O). A total of 9 effective ~(230)Th data points, ranging from 492.5 ± 43.0 ka to 62.0 ± 11.9 ka, were obtained. The depositional age of the earliest halite layer in the borehole is 592.5–563.0 ka. There were mirabilite deposits in the QB during the cold glacial environment of MIS 6. During MIS 4, the study area desiccated, with mirabilite and halite being deposited. This study suggests that mirabilite is an indicator mineral for the glacial environment in the QB, while halite deposition does not correspond well to glaciation.

关键词： evaporite deposition mirabilite Quaternary glaciation Quaternary salt lake Qaidam Basin

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Effects of Wetland Utilization Change on Spatial Distribution of Soil Nematodes in Heihe River Basin, Northwest China

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Chinese Geographical Science 2016年第3期26卷 339-351页

作者： ZHU Hongqiang MAO Zhixia LONG Zhangwei wang Yan SU Yongzhong wang xuefeng Chinese Medicinal Material College Jilin Agricultural University Northeast Institute of Geography and Agroecology Chinese Academy of Sciences Linze Inland River Basin Research Station Key Laboratory of Eco-Hydrology in Heihe River Basin Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

The first account of the effects of wetland reclamation on soil nematode assemblages were provided, three sites in Heihe River Basin of Northwest China, that is grass wetland(GW), Tamarix chinensis wetland(TW) and crop wetland(CW) treatments, were compared. Results showed that the majority of soil nematodes were presented in the 0–20 cm soil layers in CW treatments, followed by in the 20–40 cm and 40–60 cm layers in GW treatments. Plant-feeding nametodes were the most abundant trophic groups in each treatment, where GW(91.0%) > TW(88.1%) > CW(53.5%). Generic richness(GR) was lower in the TW(16) than that in GW(23) and CW(25). The combination of enrichment index(EI) and structure index(SI) showed that the soil food web in GW was more structured, and those in TW was stressed, while the enrichment soil food web was presented in the CW treatment. Several ecological indices which reflected soil community structure, diversity, Shannon-Weaver diversity(H′), Evenness(J′), Richness(GR) and modified maturity index(MMI) were found to be effective for assessing the response of soil namatode communities to soil of saline wetland reclamation. Furthermore, saline wetland reclamation also exerted great influence on the soil physical and chemical properties(p H, Electric conductivity(EC), Total organic carbon(TOC), Total nitrogen(Total-N) and Nitrate Nitrogen(N-NO3–)). These results indicated that the wetland reclamation had significantly effects on soil nematode community structure and soil properties in this study.

关键词： soil nematode spatial distribution community structure ecological index wetland exploration

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