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arXiv 2022年

作者： Zhu, Qunxi Shen, Yifei Li, Dongsheng Lin, Wei Research Institute of Intelligent Complex Systems Fudan University China Department of Electronic and Computer Engineering The Hong Kong University of Science and Technology Hong Kong Hong Kong Microsoft Research Asia China School of Mathematical Sciences State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science Institutes of Brain Science Shanghai Center for Mathematical Sciences Center for Computational Systems Biology LCNBI and Research Institute of Intelligent Complex Systems Fudan University China

Continuous-depth neural networks, such as the Neural Ordinary Differential Equations (ODEs), have aroused a great deal of interest from the communities of machine learning and data science in recent years, which bridge the connection between deep neural networks and dynamical systems. In this article, we introduce a new sort of continuous-depth neural network, called the Neural Piecewise-Constant Delay Differential Equations (PCDDEs). Here, unlike the recently proposed framework of the Neural Delay Differential Equations (DDEs), we transform the single delay into the piecewiseconstant delay(s). The Neural PCDDEs with such a transformation, on one hand, inherit the strength of universal approximating capability in Neural DDEs. On the other hand, the Neural PCDDEs, leveraging the contributions of the information from the multiple previous time steps, further promote the modeling capability without augmenting the network dimension. With such a promotion, we show that the Neural PCDDEs do outperform the several existing continuousdepth neural frameworks on the one-dimensional piecewiseconstant delay population dynamics and real-world datasets, including MNIST, CIFAR10, and *** Codes 34Kxx, 93Cxx, 92B2 © 2022, CC BY.

关键词： Ordinary differential equations

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Polymer dynamics under tension: Mean first passage time for looping

arXiv

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arXiv 2024年

作者： Laeremans, Wout den Ouden, Anne Floor Hooyberghs, Jef Ellenbroek, Wouter G. Soft Matter and Biological Physics Department of Applied Physics and Science Education Institute for Complex Molecular Systems Eindhoven University of Technology P.O. Box 513 Eindhoven5600 MB Netherlands Laboratory of Physical Chemistry Department of Chemical Engineering and Chemistry Eindhoven University of Technology P.O. Box 513 Eindhoven5600 MB Netherlands UHasselt Faculty of Sciences Data Science Institute Theory Lab Agoralaan Diepenbeek3590 Belgium

This study deals with polymer looping, an important process in many chemical and biological systems. We investigate basic questions on the looping dynamics of a polymer under tension using the freely-jointed chain (FJC) model. Previous theoretical approaches to polymer looping under tension have relied on barrier escape methods, which assume local equilibrium, an assumption that may not always hold. As a starting point we use an analytical expression for the equilibrium looping probability as a function of the number of monomers and applied force, predicting an inverse relationship between looping time and looping probability. Using molecular dynamics simulations the predictions of this theoretical approach are validated within the numerical precision achieved. We compare our predictions to those of the barrier escape approach, by way of a calculation of the mean first passage time (MFPT) for the ends of a polymer to cross. For this purpose, we derive the exact free energy landscape, but resulting temporal predictions do not agree with the observed inverse scaling. We conclude that the traditional barrier escape approach does not provide satisfactory predictions for polymer looping dynamics and that the inverse scaling with looping probability offers a more reliable alternative. Copyright © 2024, The Authors. All rights reserved.

关键词： Inverse problems

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PID Control for Aeroengine Based on Sparrow Search Algorithm

PID Control for Aeroengine Based on Sparrow Search Algorithm

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Chinese Automation Congress (CAC)

作者： Liang Xu Hao Wang Ying Liu Wei Xue Ningning Li Tianjin Key Laboratory for Control Theory & Applications in Complicated Systems and School of Electrical Engineering and Automation Tianjin University of Technology Tianjin China National Key Laboratory for Complex Systems Simulation Beijing China Beijing Aerospace Propulsion Institute Beijing China

ISBN: (纸本)9781665426480

To address the problem of aeroengine PID parameter optimization and tuning, this work employs the excellent performance of the sparrow search algorithm (SSA) with high convergence accuracy and fast convergence speed to propose a self-tuning PID control method (SSA-PID) for aeroengine parameters. Considering that the oil supply output by the actuator may have a substantial overshoot, the proposed technique adds a penalty mechanism for the overshoot at the output, designs and improves the fitness function weighted by performance indicators, and effectively avoids the possible excessive overshoot and sharp oil supply phenomenon of the engine oil supply. The SSA-PID simulates and verifies the mathematical models of the turbofan engine’ s steady-state operating points on the ground and at high altitudes. The results show that the SSA-PID control method has better parameter tuning and optimization effects, a faster speed step response, and generates a fuel supply that does not have a targe overshoot, thereby proving its effectiveness and feasibility.

关键词： PI control Oils Search problems Mathematical models Steady-state PD control Fuels

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Stability of the separable solutions for a nonlinear boundary diffusion problem

arXiv

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arXiv 2022年

作者： Jin, Tianling Xiong, Jingang Yang, Xuzhou Department of Mathematics The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong School of Mathematical Sciences Laboratory of Mathematics and Complex Systems MOE Beijing Normal University Beijing100875 China

In this paper, we study a nonlinear boundary diffusion equation of porous medium type arising from a boundary control problem. We give a complete and sharp characterization of the asymptotic behavior of its solutions,... 详细信息

关键词： Porous materials

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Exact New Mobility Edges between Critical and Localized States

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Physical Review Letters 2023年第17期131卷 176401-176401页

作者： Xin-Chi Zhou Yongjian Wang Ting-Fung Jeffrey Poon Qi Zhou Xiong-Jun Liu International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Hefei National Laboratory Hefei 230088 China School of Mathematics and Statistics Nanjing University of Science and Technology Nanjing 210094 China School of Mathematical Sciences Laboratory of Mathematics and Complex Systems MOE Beijing Normal University Beijing 100875 China Chern Institute of Mathematics and LPMC Nankai University Tianjin 300071 China International Quantum Academy Shenzhen 518048 China

The disorder systems host three types of fundamental quantum states, known as the extended, localized, and critical states, of which the critical states remain being much less explored. Here we propose a class of exactly solvable models which host a novel type of exact mobility edges (MEs) separating localized states from robust critical states, and propose experimental realization. Here the robustness refers to the stability against both single-particle perturbation and interactions in the few-body regime. The exactly solvable one-dimensional models are featured by a quasiperiodic mosaic type of both hopping terms and on-site potentials. The analytic results enable us to unambiguously obtain the critical states which otherwise require arduous numerical verification including the careful finite size scalings. The critical states and new MEs are shown to be robust, illustrating a generic mechanism unveiled here that the critical states are protected by zeros of quasiperiodic hopping terms in the thermodynamic limit. Further, we propose a novel experimental scheme to realize the exactly solvable model and the new MEs in an incommensurate Rydberg Raman superarray. This Letter may pave a way to precisely explore the critical states and new ME physics with experimental feasibility.

关键词： Anderson localization Optical lattices & traps Quantum simulation Quasicrystals Rydberg atoms & molecules Transfer matrix method

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Front Cover Image

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Energy science & Engineering 2023年第11期11卷

作者： Ali Nekoonam Morteza Montazeri-Gh Systems Simulation and Control Laboratory School of Mechanical Engineering Iran University of Science and Technology (IUST) Tehran Iran

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Quantum interference with independent single-photon sources over 300 km fiber

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Advanced Photonics 2022年第6期4卷 64-70页

作者： Xiang You Ming-Yang Zheng Si Chen Run-Ze Liu Jian Qin Mo-Chi Xu Zheng-Xuan Ge Tung-Hsun Chung Yu-Kun Qiao Yang-Fan Jiang Han-Sen Zhong Ming-Cheng Chen Hui Wang Yu-Ming He Xiu-Ping Xie Hao Li Li-Xing You Christian Schneider Juan Yin Teng-Yun Chen Mohamed Benyouce Yong-Heng Huo Sven Höfling Qiang Zhang Chao-Yang Lu Jian-Wei Pan University of Science and Technology of China School of Cyberspace SecurityHefeiChina University of Science and Technology of China Hefei National Laboratory for Physical Sciences at MicroscaleDepartment of Modern PhysicsHefeiChina University of Science and Technology of China CAS Centre for Excellence in Quantum Information and Quantum PhysicsShanghaiChina Jinan Institute of Quantum Technology JinanChina Chinese Academy of Sciences Shanghai Institute of Microsystem and Information Technology(SIMIT)State Key Laboratory of Functional Materials for InformaticsShanghaiChina Universitat Würzburg Technische PhysikPhysikalisches Instität and Wilhelm Conrad Röntgen-Center for Complex Material SystemsWürzburgGermany University of Oldenburg Institute of PhysicsOldenburgGermany University of Kassel Institute of Nanostructure Technologies and AnalyticsCINSaTKasselGermany NYU-ECNU Institute of Physics at NYU Shanghai ShanghaiChina

In the quest to realize a scalable quantum network,semiconductor quantum dots(QDs)offer distinct advantages,including high single-photon efficiency and indistinguishability,high repetition rate(tens of gigahertz with Purcell enhancement),interconnectivity with spin qubits,and a scalable on-chip ***,in the past two decades,the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%,and the distances were limited from a few meters to ***,we report quantum interference between two single photons from independent QDs separated by a 302 km optical *** single photons are generated from resonantly driven single QDs deterministically coupled to *** frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication *** observed interference visibility is 0.670.02(0.930.04)without(with)temporal *** improvements can further extend the distance to∼600 *** work represents a key step to long-distance solid-state quantum networks.

关键词： quantum networks quantum dots solid-state single-photon sources quantum frequency conversion quantum interference

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Bayesian Framework for Multi-User Cooperative Radio SLAM

Bayesian Framework for Multi-User Cooperative Radio SLAM

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IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Hang Que Jie Yang Tao Du Shuqiang Xia Chao-Kai Wen Shi Jin National Mobile Communications Research Laboratory Southeast University Nanjing China Frontiers Science Center for Mobile Information Communication and Security Southeast University Nanjing China Key Laboratory of Measurement and Control of Complex Systems of Engineering Ministry of Education Southeast University Nanjing China ZTE Corporation Shenzhen China State Key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen China Institute of Communications Engineering National Sun Yat-sen University Kaohsiung Taiwan

ISBN: (数字)9798350362244

ISBN: (纸本)9798350362251

The advancement of millimeter-wave communication technology heralds new sensing capabilities. By leveraging channel multipath parameter estimates, we can harness simultaneous localization and mapping (SLAM) for precise user equipment (UE) localization and radio map construction in 6 G communication systems. Particularly in multi-UE scenarios, SLAM empowers base stations to amalgamate the local radio maps of various UEs efficiently. This study introduces a novel Bayesian framework specifically designed for multi-UE SLAM, complemented by a tailored factor graph. We also unveil a two-stage multi-UE SLAM algorithm. Our simulation results reveal that this algorithm substantially enhances radio map construction accuracy by $\mathbf{4 8. 5 \%}$ and UE localization accuracy by $13.5 \%$, outperforming single-UE cases. Moreover, the algorithm demonstrates remarkable adaptability to environmental changes, showcasing its potential for long-term evolution in dynamic settings.

关键词： Location awareness Simultaneous localization and mapping Accuracy Communication systems Heuristic algorithms simulation Bayes methods Sensors Millimeter wave communication Land mobile radio

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Unsteady drag force on an immersed sphere oscillating near a wall

arXiv

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arXiv 2023年

作者： Zhang, Zaicheng Bertin, Vincent Essink, Martin H. Zhang, Hao Fares, Nicolas Shen, Zaiyi Bickel, Thomas Salez, Thomas Maali, Abdelhamid Univ. Bordeaux CNRS LOMA UMR 5798 Talence33405 France Physics of Fluids Group Faculty of Science and Technology Mesa+ Institute University of Twente Enschede7500 AE Netherlands State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science College of Engineering Peking University Beijing100871 China

The unsteady hydrodynamic drag exerted on an oscillating sphere near a planar wall is addressed experimentally, theoretically, and numerically. The experiments are performed by using colloidal-probe Atomic Force Microscopy (AFM) in thermal noise mode. The natural resonance frequencies and quality factors are extracted from the measurement of the power spectrum density of the probe oscillation for a broad range of gap distances and Womersley numbers. The shift in the natural resonance frequency of the colloidal probe as the probe goes close to a solid wall infers the wall-induced variations of the effective mass of the probe. Interestingly, a crossover from a positive to a negative shift is observed as the Womersley number increases. In order to rationalize the results, the confined unsteady Stokes equation is solved numerically using a finite-element method, as well as asymptotic calculations. The in-phase and out-of-phase terms of the hydrodynamic drag acting on the sphere are obtained and agree well to the experimental results. All together, the experimental, theoretical, and numerical results show that the hydrodynamic force felt by an immersed sphere oscillating near a wall is highly dependent on the Womersley number. Copyright © 2023, The Authors. All rights reserved.

关键词： Spheres

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A Systematic Study of a Droplet Breakup Process in Decaying Homogeneous Isotropic Turbulence Using a Mesoscopic simulation Approach

SSRN

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SSRN 2022年

作者： Lai, Jun Chen, Tao Zhang, Shengqi Xiao, Zuoli Chen, Shiyi Wang, Lian-Ping State Key Laboratory for Turbulence and Complex Systems College of engineering Peking University Beijing100871 China Guangdong Provincial Key Laboratory of Turbulence Research and Applications Center for Complex Flows and Soft Matter Research Department of Mechanics and Aerospace Engineering Southern University of Science and Technology Shenzhen518055 China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid Mechanics and Engineering Applications Southern University of Science and Technology Shenzhen518055 China

The breakup of a spherical droplet in a decaying homogeneous isotropic turbulence is studied by solving the Cahn-Hilliard-Navier-Stokes equations. The key physical parameters of the system include the volume fraction (6.54%), the initial Weber number (We=21.7), and the initial Taylor microscale Reynolds number (Re_\lambda=58). Due to the turbulence decay and droplet breakup, the dynamics of the system switches from kinetic energy-dominated to interfacial free energy-dominated, providing a great opportunity to study the interactions of these two forms of energy and their effects on the viscous dissipation. Three distinct stages of droplet evolution, namely, the deformation stage, the breakup stage, and the restoration stage, are identified and then analyzed systematically from several perspectives: (1) a geometric perspective concerning the size and number of droplets, (2) a dynamic perspective concerning the evolution of local velocity and vorticity at the fluid-fluid interface, (3) a global perspective concerning the evolution of average kinetic energy, dissipation rate and free energy of the system, and (4) transfer of kinetic energy across different length scales and different radii relative to initial droplet center. It is found that the ending time of the breakup stage can be estimated by the Hinze criterion. The kinetic energy of the two-phase flow during the breakup stage is found to have a power-law decay with an exponent -1.76, compared to -1.65 for the single-phase flow, mainly due to the enhanced viscous dissipation generated by the daughter droplets. Energy spectra of the two-phase flow show power-law decay, with a slope between -4 and -3, at high wave numbers, both in the Fourier spectral space and in the spherical harmonics space. © 2022, The Authors. All rights reserved.

关键词： Two phase flow

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