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Threshold and decay properties of transient isolated turbulent band in plane Couette flow

applied mathematics and Mechanics(English Edition) 2019年第10期40卷 1449-1456页

作者： Jianzhou LU Jianjun TAO Weitao ZHOU Xiangming XIONG CAPT-HEDPS SKLTCS Collaborative Innovation Center of IFSA Department of Mechanics and Engineering Science College of Engineering Peking University Beijing 100871 China The Program in Applied and Computational Mathematics Princeton University Princeton NJ 08544 U. S.A.

By direct numerical simulations of the plane Couette flow (PCF) in a large computational domain, it is shown that an isolated turbulent band decays monotonically at low Reynolds numbers but experiences transient growth before the eventual relaminarization at moderate Reynolds numbers. The lower bound Reynolds number of the transient-growth regime is determined as 286. The width, length, and tilt angle of the iso- lated band structure are defined based on the disturbance kinetic energy in the mid-plane, and the geometric characteristics of the band can be described with a tilted rectangle. It is illustrated that before its eventual fragmentation, the isolated turbulent band decays in a style of longitudinal contraction, where the center, width, and tilt angle of the band keep almost constant but the band length contracts with a statistically constant velocity.

关键词： plane Couette flow (PCF) subcritical transition turbulent band

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Electro-osmotic instability of concentration enrichment in curved geometries for an aqueous electrolyte

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Physical Review Fluids 2020年第9期5卷 091701(R)-091701(R)页

作者： Bingrui Xu Zhibo Gu Wei Liu Peng Huo Yueting Zhou S. M. Rubinstein M. Z. Bazant B. Zaltzman I. Rubinstein Daosheng Deng Department of Aeronautics and Astronautics Fudan University Shanghai 200433 China School of Aerospace Engineering and Applied Mechanics Tongji University Shanghai 200092 China John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Chemical Engineering and Department of Mathematics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Mathematics and the BIDR Ben-Gurion University of the Negev Sede Boqer Campus Sede Boqer 8499000 Israel

We report that an electro-osmotic instability of concentration enrichment in curved geometries for an aqueous electrolyte, as opposed to the well-known one, is initiated exclusively at the enriched interface (anode), rather than at the depleted one (cathode). For this instability, the limitation of an unrealistically high material Peclet number in planar geometry is eliminated by the strong electric field arising from the line charge singularity. In a model setup of concentric circular electrodes, we show by stability analysis, numerical simulation, and experimental visualization that instability occurs at the inner anode, below a critical radius of curvature. The stability criterion is also formulated in terms of a critical electric field and extended to arbitrary (two-dimensional) geometries by conformal mapping. This discovery suggests that transport may be enhanced in processes limited by salt enrichment, such as reverse osmosis, by triggering this instability with needlelike electrodes.

关键词： Electrokinetic flows engineering Flow instability

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Publisher's Note: “Reacting and non-reacting, three-dimensional shear layers with spanwise stretching” [Phys. Fluids 34, 123602 (2022)]

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Physics of Fluids 2023年第1期35卷

作者： Jonathan L. Palafoutas William A. Sirignano 1Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08540 USA 2Department of Mechanical and Aerospace Engineering University of California Irvine Irvine California 92697 USA

This article was published online on 2 December 2022 with errors throughout the paper. All the derivative terms had the wrong denominator; the denominators were

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Position: Bayesian deep learning is needed in the age of large-scale AI 24

Position: Bayesian deep learning is needed in the age of lar...

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Proceedings of the 41st International Conference on Machine Learning

作者： Theodore Papamarkou Maria Skoularidou Konstantina Palla Laurence Aitchison Julyan Arbel David Dunson Maurizio Filippone Vincent Fortuin Philipp Hennig José Miguel Hernández-Lobato Aliaksandr Hubin Alexander Immer Theofanis Karaletsos Mohammad Emtiyaz Khan Agustinus Kristiadi Yingzhen Li Stephan Mandt Christopher Nemeth Michael A. Osborne Tim G. J. Rudner David Rügamer Yee Whye Teh Max Welling Andrew Gordon Wilson Ruqi Zhang Department of Mathematics The University of Manchester Manchester UK Eric and Wendy Schmidt Center Broad Institute of MIT and Harvard Cambridge Spotify London UK Computational Neuroscience Unit University of Bristol Bristol UK Centre Inria de l'Université Grenoble Alpes Grenoble France Department of Statistical Science Duke University Statistics Program KAUST Saudi Arabia Helmholtz AI Munich Germany and Department of Computer Science Technical University of Munich Munich Germany and Munich Center for Machine Learning Munich Germany Tübingen AI Center University of Tübingen Tübingen Germany Department of Engineering University of Cambridge Cambridge UK Department of Mathematics University of Oslo Oslo Norway and Bioinformatics and Applied Statistics Norwegian University of Life Sciences Ås Norway Department of Computer Science ETH Zurich Switzerland Chan Zuckerberg Initiative California Center for Advanced Intelligence Project RIKEN Tokyo Japan Vector Institute Toronto Canada Department of Computing Imperial College London London UK Department of Computer Science UC Irvine Irvine Department of Mathematics and Statistics Lancaster University Lancaster UK Department of Engineering Science University of Oxford Oxford UK Center for Data Science New York University New York Munich Center for Machine Learning Munich Germany and Department of Statistics LMU Munich Munich Germany DeepMind London UK and Department of Statistics University of Oxford Oxford UK Informatics Institute University of Amsterdam Amsterdam Netherlands Courant Institute of Mathematical Sciences and Center for Data Science Computer Science Department New York University New York Department of Computer Science Purdue University West Lafayette

In the current landscape of deep learning research, there is a predominant emphasis on achieving high predictive accuracy in supervised tasks involving large image and language datasets. However, a broader perspective reveals a multitude of overlooked metrics, tasks, and data types, such as uncertainty, active and continual learning, and scientific data, that demand attention. Bayesian deep learning (BDL) constitutes a promising avenue, offering advantages across these diverse settings. This paper posits that BDL can elevate the capabilities of deep learning. It revisits the strengths of BDL, acknowledges existing challenges, and highlights some exciting research avenues aimed at addressing these obstacles. Looking ahead, the discussion focuses on possible ways to combine large-scale foundation models with BDL to unlock their full potential.

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Exploiting self-organized criticality in strongly stratified turbulence

arXiv

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arXiv 2021年

作者： Chini, Gregory P. Michel, Guillaume Julien, Keith Rocha, Cesar B. Caulfield, Colm-Cille P. Program in Integrated Applied Mathematics University of New Hampshire DurhamNH03824 United States Department of Mechanical Engineering University of New Hampshire DurhamNH03824 United States Institut Jean Le Rond d’Alembert Sorbonne Université CNRS UMR 7190 ParisF-75005 France Department of Applied Mathematics University of Colorado BoulderCO80309 United States Department of Marine Sciences University of Connecticut StorrsCT06269 United States BP Institute Department of Applied Mathematics & Theoretical Physics Cambridge University CambridgeCB3 0WA United Kingdom

A multiscale reduced description of turbulent free shear flows in the presence of strong stabilizing density stratification is derived via asymptotic analysis of the Boussinesq equations in the simultaneous limits of small Froude and large Reynolds numbers. The analysis explicitly recognizes the occurrence of dynamics on disparate spatiotemporal scales, yielding simplified partial differential equations governing the coupled evolution of slow large-scale hydrostatic flows and fast small-scale isotropic instabilities and internal waves. The dynamics captured by the coupled reduced equations is illustrated in the context of two-dimensional strongly stratified Kolmogorov flow. A noteworthy feature of the reduced model is that the fluctuations are constrained to satisfy quasilinear (QL) dynamics about the comparably slowly-varying large-scale fields. Crucially, this QL reduction is not invoked as an ad hoc closure approximation, but rather is derived in a physically relevant and mathematically consistent distinguished limit. Further analysis of the resulting slow-fast QL system shows how the amplitude of the fast stratified-shear instabilities is slaved to the slowly-evolving mean fields to ensure the marginal stability of the latter. Physically, this marginal stability condition appears to be compatible with recent evidence of self-organized criticality in both observations and simulations of stratified turbulence. Algorithmically, the slaving of the fluctuation fields enables numerical simulations to be time-evolved strictly on the slow time scale of the hydrostatic flow. The reduced equations thus provide a solid mathematical foundation for future studies of three-dimensional strongly stratified turbulence in extreme parameter regimes of geophysical relevance and suggest avenues for new sub-grid-scale parameterizations. Copyright © 2021, The Authors. All rights reserved.

关键词： Asymptotic analysis

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The solution of simultaneous dual integral equations involving fox’s H-function

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AIP Conference Proceedings 2023年第1期2768卷

作者： A. K. Awasthi Rachna Rajendra Kumar Tripathi Homan Emadifar Department of Mathematics School of Chemical Engineering and Physical Sciences Lovely Professional University Phagwara 144411 India Applied science and Humanities (Mathematics) Faculty of Engineering and Technology Khwaja Moinuddin Chishti Language University Lucknow 226013 India Department of Mathematics Hamedan Branch Islamic Azad University Hamedan 65816 Iran MEU Research Unit Middle East University Amman Jordan

Simultaneous dual integral equations arise in the formulation of a great variety of mixed boundary value problems of semi-infinite domains involving one or more than one unknown function, such as the problems in electrostatics, viscoelastic and electrostatics. There has been correspondingly less work of this nature on integral equations associated with H-functions. So we have considered the dual integral equations involving Fox’s H-function. The H-function can be used to solve a variety of problems in physics, engineering, and statistics. The present paper contains a problem of the formal solution of certain simultaneous dual integral equations involving Fox’s H-function. The simultaneous dual integral equations were studied earlier by Dwivedi, Erdogen and Bahar. In the latter case, the dual integral equations are transformed by the application of fractional integral operators into two others with a common kernel, which turns out to be a symmetrical. The formal solution, investigated earlier by Srivastava and Modi, is then readily obtained. The same method has also been adopted by the authors Fox, Srivastava, Srivastava and Kushwaha for the solution of certain dual integral equations involving H-functions.

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Controlled synthetic chirality in macroscopic assemblies of carbon nanotubes

arXiv

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arXiv 2023年

作者： Doumani, Jacques Lou, Minhan Dewey, Oliver Hong, Nina Fan, Jichao Baydin, Andrey Yomogida, Yohei Yanagi, Kazuhiro Pasquali, Matteo Saito, Riichiro Kono, Junichiro Gao, Weilu Department of Electrical and Computer Engineering Rice University HoustonTX United States Applied Physics Graduate Program Smalley–Curl Institute Rice University HoustonTX United States Department of Electrical and Computer Engineering The University of Utah Salt Lake CityUT United States Carbon Hub Rice University HoustonTX United States Department of Chemical and Biomolecular Engineering Rice University HoustonTX United States J.A. Woollam Co. Inc. LincolnNE United States Smalley–Curl Institute Rice University HoustonTX United States Department of Physics Tokyo Metropolitan University Tokyo Japan Department of Chemistry Rice University HoustonTX United States Department of Materials Science and NanoEngineering Rice University HoustonTX United States Department of Physics Tohoku University Sendai Japan Department Physics and Astronomy Rice University HoustonTX United States

There is an emerging recognition that successful utilization of chiral degrees of freedom can bring new scientific and technological opportunities to diverse research areas. Hence, methods are being sought for creating artificial matter with controllable chirality in an uncomplicated and reproducible manner. Here, we report the development of two straightforward methods for fabricating wafer-scale chiral architectures of ordered carbon nanotubes (CNTs) with tunable and giant circular dichroism (CD). Both methods employ simple approaches, (i) mechanical rotation and (ii) twist-stacking, based on controlled vacuum filtration and do not involve any sophisticated nanofabrication processes. We used a racemic mixture of CNTs as the starting material, so the intrinsic chirality of chiral CNTs is not responsible for the observed chirality. In particular, by controlling the stacking angle and handedness in (ii), we were able to maximize the CD response and achieve a record-high deep-ultraviolet ellipticity of 40 ± 1 mdeg/nm. Our theoretical simulations using the transfer matrix method reproduce the salient features of the experimentally observed CD spectra and further predict that a film of twist-stacked CNTs with an optimized thickness will exhibit an ellipticity as high as 150 mdeg/nm. The created wafer-scale objects represent a new class of synthetic chiral matter consisting of ordered quantum wires whose macroscopic properties are governed by nanoscopic electronic signatures such as van Hove singularities. These artificial structures with engineered chirality will not only provide playgrounds for uncovering new chiral phenomena but also open up new opportunities for developing high-performance chiral photonic and optoelectronic devices. © 2023, CC BY.

关键词： Carbon nanotubes

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Integrability of Goldilocks quantum cellular automata

arXiv

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arXiv 2024年

作者： Hillberry, Logan E. Piroli, Lorenzo Vernier, Eric Halpern, Nicole Yunger Prosen, Tomaž Carr, Lincoln D. Department of Physics The University of Texas at Austin AustinTX78712 United States Dipartimento di Fisica e Astronomia Università di Bologna INFN Sezione di Bologna via Irnerio 46 BolognaI-40126 Italy Laboratoire de Probabilités Statistique et Modélisation CNRS Université Paris Cité Sorbonne Université Paris France Joint Center for Quantum Information and Computer Science NIST University of Maryland College ParkMD20742 United States Institute for Physical Science and Technology University of Maryland College ParkMD20742 United States Faculty of Mathematics and Physics University of Ljubljana Jadranska 19 LjubljanaSI-1000 Slovenia Institute of Mathematics Physics and Mechanics Jadranska 19 LjubljanaSI-1000 Slovenia Quantum Engineering Program Colorado School of Mines GoldenCO80401 United States Department of Physics Colorado School of Mines GoldenCO80401 United States Department of Applied Mathematics and Statistics Colorado School of Mines GoldenCO80401 United States

Goldilocks quantum cellular automata (QCA) have been simulated on quantum hardware and produce emergent small-world correlation networks. In Goldilocks QCA, a single-qubit unitary is applied to each qubit in a one-dimensional chain subject to a balance constraint: a qubit is updated if its neighbors are in opposite basis states. Here, we prove that a subclass of Goldilocks QCA—including the one implemented experimentally—map onto free fermions and therefore can be classically simulated efficiently. We support this claim with two independent proofs, one involving a Jordan–Wigner transformation and one mapping the integrable six-vertex model to QCA. We compute local conserved quantities of these QCA and predict experimentally measurable expectation values. These calculations can be applied to test large digital quantum computers against known solutions. In contrast, typical Goldilocks QCA have equilibration properties and quasienergy-level statistics that suggest nonintegrability. Still, the latter QCA conserve one quantity useful for error mitigation. Our work provides a parametric quantum circuit with tunable integrability properties with which to test quantum hardware. © 2024, CC BY.

关键词： Qubits

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Effect of functionalized nanodiamonds and surfactants mediation on the nanofiltration performance of polyamide thin-film nanocomposite membranes

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Desalination 2023年 555卷

作者： Subrahmanya, T.M. Lin, Jing-Yang Widakdo, Januar Austria, Hannah Faye M. Owen-Setiawan Chiao, Yu-Hsuan Huang, Tsung-Han Hung, Wei-Song Matsuyama, Hideto Lee, Kueir-Rarn Lai, Juin-Yih Advanced Membrane Materials Research Center Graduate Institute of Applied science and Technology National Taiwan University of Science and Technology Taipei10607 Taiwan Department of Physics Faculty of Mathematics and Natural Sciences Universitas Indonesia Depok16424 Indonesia Department of Chemical Engineering and Materials Science Yuan Ze University Taoyuan32023 Taiwan Research Center for Membrane and Film Technology Kobe University 1-1 Rokkodai Nada Kobe657-8501 Japan R&D Center for Membrane Technology Chung Yuan University Chung-Li32023 Taiwan

Thin film nanocomposite (TFN) membranes have drawn intensive attention for desalination. Herein, we investigate the effect of addition of different kinds of functionalized (Amine, Carboxylic acid, Hydrogen) nanodiamonds (NDs) and their dispersion enhanced by surfactants mediation on polypiperazineamide selective layer synthesized on polyamide membrane via Piperazine (PIP) and Trimesoyl chloride (TMC) interfacial polymerization (IP). The addition of functionalized NDs not only enhanced the surface roughness, hydrophilicity, and degree of crosslinking of selective layer but also enhanced the water flux and salt rejection performance of the membranes. The optimum NH2-ND400/PIP/TMC membrane enhanced the water flux by 14 % and MgSO4 rejection by 2.4 % with respect to the conventional PIP/TMC membrane. To further enhance the performance, different chain length surfactants such as Sodium Octyl Sulfate (SOS) and Sodium Dodecyl Sulfate (SDS) were added to the aqueous phase of IP system. The optimum SDS1/NH2-ND400/PIP/TMC membrane showed improved flux and MgSO4 rejection of 8.87 Lm−2h−1b−1 and 98.68 %. It was further investigated for long term stability performance, which resulted in maximum flux and salt rejection of 15 Lm−2h−1b−1 and 99.57 % respectively, leading to increase of water flux by 87.5 % and MgSO4 rejection by 0.5 % with respect to the conventional PIP/TMC membrane. Overall, the highlight was that the SDS addition improved the membrane performance with well retained stability, indicating that the SDS has significantly improved the degree of crosslinking of selective layer via improved dispersion of PIP and NH2-NDs in aqueous phase during IP, making it mechanically more stable, hydrophilic and effective for MgSO4 rejection as compared to the conventional PIP/TMC membrane. The SDS1/NH2-ND400/PIP/TMC membranes show great potential to be used in nanofiltration. © 2023

关键词： Nanofiltration

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Synthesis of a biocomposite based on Kluwih (Artocarpus camansi) seed starch incorporated with carrageenan as a functional additive and cellulose nanofiber filler

Case Studies in Chemical and Environmental Engineering

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Case Studies in chemical and Environmental engineering 2025年 11卷

作者： Hidayat, Fadlan Indarti, Eti Rahmi Arahman, Nasrul Doctoral Program of Agricultural Science Postgraduate School Universitas Syiah Kuala Banda Aceh 23111 Indonesia Department of Agricultural Product Technology Agriculture Faculty Universitas Syiah Kuala Banda Aceh 23111 Indonesia Atsiri Research Center PUI Universitas Syiah Kuala Jl. Syeh A Rauf No. 5 Darussalam Banda Aceh 23111 Indonesia Department of Chemistry Faculty of Mathematics and Natural Sciences Universitas Syiah Kuala Banda Aceh 23111 Indonesia Department of Chemical Engineering Engineering Faculty Universitas Syiah Kuala Banda Aceh 23111 Indonesia Research Center for Environmental and Natural Resources Universitas Syiah Kuala Jl. Hamzah Fansuri No. 4 Darussalam Banda Aceh 23111 Indonesia

The widespread use of synthetic plastics causes environmental issues because of their nondegradability. In this study, biocomposite from Kluwih seed starch were incorporated with carrageenan and cellulose nanofiber (CNF) to improve their mechanical properties. CNFs were prepared using the TEMPO method with ultrasonication. The variables included starch (1, 1.5, 2 g), carrageenan (3, 4.5, 6 g), and CNF (0.006, 0.12, 0.18 g). The mechanical properties of the biocomposite were optimized using RSM. Zeta potential analysis confirmed the stability of CNFs, and XRD and FTIR analyses revealed improved crystallinity and functional groups. The tensile strength of the biocomposites was 12.08 kgf/mm², which is suitable for sustainable packaging applications. © 2025

关键词： Biocomposite Carrageenan Cellulose nanofiber Kluwih seeds starch Tensile strength

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