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arXiv 2025年

作者： Goodwin, Zachary A.H. Markiewitz, Daniel M. Wu, Qisheng Qi, Yue Bazant, Martin Z. Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Department of Chemical Engineering Massachusetts Institute of Technology CambridgeMA02139 United States School of Engineering Brown University ProvidenceRI02912 United States Department of Mathematics Massachusetts Institute of Technology CambridgeMA02139 United States

The solvation environments of Li+ in conventional non-aqueous battery electrolytes, such as LiPF6 in mixtures of ethylene carbaronate (EC) and ethyl methyl carbonate (EMC), are often used to rationalize the transport properties of electrolytes and solid electrolyte interphase (SEI) formation. In the SEI, the solvation environments in the compact electrical double layer (EDL) next to the electrode, also known as the Helmholtz layer, determine (partially) what species can react to form the SEI, with bulk solvation environments often being used as a proxy. Here we develop and test a theory of cation solvation in the Helmholtz layer of non-aqueous Li-ion battery electrolytes. First, we validate the theory against bulk and diffuse EDL atomistic molecular dynamics (MD) simulations of LiPF6 EC/EMC mixtures as a function of surface charge, where we find the theory can capture the solvation environments well. Next we turn to the Helmholtz layer, where we find that the main effect of the solvation structures next to the electrode is an apparent reduction in the number of binding sites between Li+ and the solvents, again where we find good agreement with our developed theory. Finally, by solving a simplified version of the theory, we find that the probability of Li+ binding to each solvent remains equal to the bulk probability, suggesting that the bulk solvation environments are a reasonable place to start when understanding new battery electrolytes. Our developed formalism can be parameterized from bulk MD simulations and used to predict the solvation environments in the Helmholtz layer, which can be used to determine what could react and form the SEI. © 2025, CC BY-SA.

关键词： Electrolytes

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State Estimation Methods for Continuous-Discrete Nonlinear Systems involving Stochastic Differential Equations

arXiv

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arXiv 2022年

作者： Nielsen, Marcus Krogh Ritschel, Tobias K.S. Christensen, Ib Dragheim, Jess Huusom, Jakob Kjøbsted Gernaey, Krist V. Jørgensen, John Bagterp The Department of Applied Mathematics and Computer Science The Department of Chemical and Biochemical Engineering Technical University of Denmark Kgs. Lyngby DK-2800 Denmark Unibio A/S RoskildeDK-4000 Denmark

In this work, we present methods for state estimation in continuous-discrete nonlinear systems involving stochastic differential equations. We present the extended Kalman filter, the unscented Kalman filter, the ensemble Kalman filter, and a particle filter. We implement the state estimation methods in Matlab. We evaluate the performance of the methods on a simulation of the modified four-tank system. We implement the state estimation methods for non-stiff systems, i.e., using an explicit numerical integration scheme. The implementation of the extended Kalman filter utilises the Joseph stabilising form for numerical stability. We evaluate the accuracy of the state estimation methods in terms of the mean absolute percentage error over the simulation horizon. We show that each method successfully estimates the states and unmeasured disturbances of the simulated modified four-tank system. Finally, we present conclusions. Copyright © 2022, The Authors. All rights reserved.

关键词： Extended Kalman filters

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Following marginal stability manifolds in quasilinear dynamical reductions of multiscale flows in two space dimensions

arXiv

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arXiv 2024年

作者： Ferraro, Alessia Chini, Gregory P. Schneider, Gregory M. École Polytechnique Fédérale de Lausanne LausanneCH-1015 Switzerland Nordita Royal Institute of Technology Stockholm University Stockholm106 91 Sweden Department of Mechanical Engineering and Program in Integrated Applied Mathematics University of New Hampshire DurhamNH03824 United States

A two-dimensional (2D) extension of a recently developed formalism for slow-fast quasilinear (QL) systems subject to fast instabilities is derived. Prior work has demonstrated that the emergent dynamics of these systems is characterized by a slow evolution of (suitably defined) mean fields coupled to marginally stable, fast fluctuation fields. By exploiting this emergent behavior, an efficient hybrid fast-eigenvalue/slow-initial-value solution algorithm can be developed in which the amplitude of the fast fluctuations is slaved to the slowly evolving mean fields to ensure marginal stability-and temporal scale separation-is maintained. For 2D systems that are spatially-extended in one direction, the fluctuation eigenfunctions are labeled by their Fourier wavenumbers characterizing spatial variability in that direction, and the marginal mode(s) also must coincide with the fastest-growing mode(s) over all admissible Fourier wavenumbers. Here, we introduce two alternative but equivalent procedures for deriving an ordinary differential equation governing the slow evolution of the wavenumber of the fastest-growing fluctuation mode that simultaneously must be slaved to the mean dynamics to ensure the mode has zero growth rate. We illustrate the procedure in the context of a 2D model partial differential equation that shares certain attributes with the equations governing strongly stratified shear flows and other strongly constrained forms of geophysical turbulence in extreme parameter regimes. The slaved evolution follows one or more marginal stability manifolds, which constitute select state-space structures that are not invariant under the full flow dynamics yet capture quasi-coherent structures in physical space in a manner analogous to invariant solutions identified in, e.g., transitionally-turbulent shear flows. Accordingly, we propose that marginal stability manifolds are central organizing structures in a dynamical systems description of certain classes of multiscale

关键词： Ordinary differential equations

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Aspect-ratio dependent heat transport by baroclinic acoustic streaming

arXiv

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arXiv 2024年

作者： Massih, Jacques Abdul Mushthaq, Remil Michel, Guillaume Chini, Gregory P. Program in Integrated Applied Mathematics University of New Hampshire DurhamNH03824 United States Department of Mechanical Engineering University of New Hampshire DurhamNH03824 United States Sorbonne Université CNRS Institut Jean Le Rond d’Alembert ParisF-75005 France

Standing acoustic waves have been known to generate Eulerian time-mean ‘streaming’ flows at least since the seminal investigation of Lord Rayleigh in the 1880s. Nevertheless, a recent body of numerical and experimental evidence has shown that inhomogeneities in the ambient density distribution lead to much faster flows than arise in classical Rayleigh streaming. The emergence of these unusually strong flows creates new opportunities to enhance heat transfer in systems in which convective cooling cannot otherwise be easily achieved. To assess this possibility, a theoretical study of acoustic streaming in an ideal gas confined in a rectangular channel with top and bottom walls maintained at fixed but differing temperatures is performed. A two time-scale system of equations is utilized to efficiently capture the coupling between the fast acoustic waves and the slowly evolving streaming flow, enabling strongly nonlinear regimes to be accessed. A large suite of numerical simulations is carried out to probe the streaming dynamics, to highlight the critical role played by baroclinically-generated wave vorticity and to quantify the additional heat flux induced by the standing acoustic wave. Proper treatment of the two-way coupling between the waves and mean flow is found to be essential for convergence to a self-consistent steady-state, and the variation of the resulting acoustically-enhanced steady-state heat flux with both the amplitude of the acoustic wave and the O(1) aspect ratio of the channel is documented. For certain parameters, heat fluxes almost two orders of magnitude larger than those realizable by conduction alone can be attained. © 2024, CC BY-SA.

关键词： Heat flux

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Modeling of Measurement Error in Financial Returns Data

arXiv

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arXiv 2024年

作者： Jasra, Ajay Maama, Mohamed Mijatović, Aleksandar School of Data Science The Chinese University of Hong Kong Shenzhen China Applied Mathematics and Computational Science Program Computer Electrical and Mathematical Sciences and Engineering Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia Department of Statistics University of Warwick United Kingdom

In this paper we consider the modeling of measurement error for fund returns data. In particular, given access to a time-series of discretely observed log-returns and the associated maximum over the observation period, we develop a stochastic model which models the true log-returns and maximum via a Lévy process and the data as a measurement error there-of. The main technical difficulty of trying to infer this model, for instance Bayesian parameter estimation, is that the joint transition density of the return and maximum is seldom known, nor can it be simulated exactly. Based upon the novel stick breaking representation of [12] we provide an approximation of the model. We develop a Markov chain Monte Carlo (MCMC) algorithm to sample from the Bayesian posterior of the approximated posterior and then extend this to a multilevel MCMC method which can reduce the computational cost to approximate posterior expectations, relative to ordinary MCMC. We implement our methodology on several applications including for real data. Copyright © 2024, The Authors. All rights reserved.

关键词： Markov chains

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Mathematical modelling of flow and adsorption in a gas chromatograph

arXiv

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arXiv 2024年

作者： Cabrera-Codony, A. Valverde, A. Born, K. Noreldin, O.A.I. Myers, T.G. LEQUIA Institute of the Environment Universitat de Girona Spain Department of Chemical Engineering Universitat Politècnica de Catalunya Spain School of Computer Science and Applied Mathematics University of the Witwatersrand Johannesburg South Africa Department of Mathematical Sciences University of Zululand South Africa Centre de Recerca Matemàtica Barcelona Spain

In this paper, a mathematical model is developed to describe the evolution of the concentration of compounds through a gas chromatography column. The model couples mass balances and kinetic equations for all components. Both single and multiple-component cases are considered with constant or variable velocity. Non-dimensionalisation indicates the small effect of diffusion. The system where diffusion is neglected is analysed using Laplace transforms. In the multiple-component case, it is demonstrated that the competition between the compounds is negligible and the equations may be decoupled. This reduces the problem to solving a single integral equation to determine the concentration profile for all components (since they are scaled versions of each other). For a given analyte, we then only two parameters need to be fitted to the data. To verify this approach, the full governing equations are also solved numerically using the finite difference method and a global adaptive quadrature method to integrate the Laplace transformation. Comparison with the Laplace solution verifies the high degree of accuracy of the simpler Laplace form. The Laplace solution is then verified against experimental data from BTEX chromatography. This novel method, which involves solving a single equation and fitting parameters in pairs for individual components, is highly efficient. It is significantly faster and simpler than the full numerical solution and avoids the computationally expensive methods that would normally be used to fit all curves at the same time. © 2024, CC BY-NC-SA.

关键词： Finite difference method

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Enzymatic Synthesis, Characterization, and Application of Sucrose Ester Derived from Palm Kernel Oil Methyl Ester as Food Emulsifier

SSRN

引用

SSRN 2024年

作者： Rahmi, Rahmi Kurniasih, Eka Darusman, Darusman Supardan, Muhammad Dani Doctoral Program in Agricultural Science Universitas Syiah Kuala Banda Aceh23111 Indonesia Department of Chemistry Faculty of Mathematics and Natural Science Universitas Syiah Kuala Banda Aceh23111 Indonesia Department of Soil Science Faculty of Agriculture Universitas Syiah Kuala Banda Aceh23111 Indonesia Department of Chemical Engineering Faculty of Engineering Universitas Syiah Kuala Banda Aceh23111 Indonesia

Sucrose ester (SEs) is an emulsifier that is widely used in many kinds of food products. Its application improves flavor, color, and texture. SEs was synthesized from palm kernel oil methyl ester (PKOME) and sucrose using Candida antarctica lipase enzyme as a biocatalyst. The enzymatic synthesis occurred at 30°C, with a Candida antarctica load of 50 mg, and a stirring speed of 250 rpm. The crude SEs was purified by vacuum filtration and then dried at 35-40°C for 6-8 h. This study aimed to obtain the optimal substrate conversion depending on 2 affecting factors: reaction time and sucrose concentration. Determination of the reaction time was carried out at 2-20 h, and sucrose concentration at 100-1,000 ***-1. The substrate conversion was determined using the refractive index (oBrix value) and then validated with a spectrophotometer-UV. The study found that an optimal substrate conversion of 87.8% had been achieved at a sucrose concentration of 400 ***-1, lasted for 12 h. The characteristics of optimal SEs were as follows: SEs purity was 91.82%, free sucrose was 1.75%, acid value was 2.93%, and free methanol was 0.11%. SEs was an o/w emulsifier with an HLB value of 12.35. The functional groups of SEs were O-H, C-H2, C-H, C=O, and C-O, which differed from substrates. In addition, applying SEs of 0.6% (w/v) in a coconut milk emulsion enriched with cooking oil maintains emulsion stability with a creaming index of 54.30% and a pH of 5.75 for 7 days of storage. © 2024, The Authors. All rights reserved.

关键词： Sugar (sucrose)

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BEAST DB: Grand-Canonical Database of Electrocatalyst Properties

arXiv

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arXiv 2024年

作者： Tezak, Cooper Clary, Jacob Gerits, Sophie Quinton, Joshua Rich, Benjamin Singstock, Nicholas Alherz, Abdulaziz Aubry, Taylor Clark, Struan Hurst, Rachel Ben, Mauro Del Sutton, Christopher Sundararaman, Ravishankar Musgrave, Charles Vigil-Fowler, Derek Department of Chemical and Biological Engineering University of Colorado Boulder BoulderCO80309 United States Materials Chemical and Computational Science Directorate National Renewable Energy Laboratory GoldenCO80401 United States Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute TroyNY12180 United States Department of Chemistry University of Colorado Boulder BoulderCO80309 United States Department of Mechanical Engineering University of Colorado Boulder BoulderCO80309 United States Department of Chemical Engineering College of Engineering and Petroleum Kuwait University Safat13060 Kuwait Applied Mathematics & Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Chemistry and Biochemistry University of South Carolina ColumbiaSC29208 United States Department of Materials Science and Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Materials Science and Engineering Program University of Colorado Boulder BoulderCO80309 United States Renewable and Sustainable Energy Institute University of Colorado Boulder BoulderCO80309 United States Department of Chemical Engineering University of Utah Salt Lake CityUT84112 United States

We present BEAST DB, an open-source database comprised of ab initio electrochemical data computed using grand-canonical density functional theory in implicit solvent at consistent calculation parameters. The database contains over 20,000 surface calculations and covers a broad set of heterogenous catalyst materials and electrochemical reactions. Calculations were performed at self-consistent fixed potential as well as constant charge to facilitate comparisons to the computational hydrogen electrode. This article presents common use cases of the database to rationalize trends in catalyst activity, screen catalyst material spaces, understand elementary mechanistic steps, analyze electronic structure, and train machine learning models to predict higher fidelity properties. Users can interact graphically with the database by querying for individual calculations to gain granular understanding of reaction steps or by querying for an entire reaction pathway on a given material using an interactive reaction pathway tool. BEAST DB will be periodically updated, with planned future updates to include advanced electronic structure data, surface speciation studies, and greater reaction coverage. Copyright © 2024, The Authors. All rights reserved.

关键词： Database systems

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Dermatological Diagnostics: A Unified Deep Learning Framework for Skin Lesion and Cancer Classification

Dermatological Diagnostics: A Unified Deep Learning Framewor...

引用

Advances in Computing, Communication and Networking (ICAC2N), International Conference on

作者： Vinod Kumar Isha Jain Durga Sritha Dongla Shivangi Rai Vani Rastogi Eva Kaushik Rohit Kaushik School of Engineering & Applied Science The George Washington University Washington D.C USA Computer Science & Engineering Department Dr. Akhilesh Das Gupta Institute of Technology and Management New Delhi India Computer Science & Engineering Department Gandhi Institute of Technology and Management Visakhapatnam Andhra Pradesh Data Scientist DXC Technology Noida India CS and Mathematics Department Data Analytics Program University of Illinois Springfield USA

ISBN: (数字)9798350356816

ISBN: (纸本)9798350356823

Skin pathologies encompass a spectrum of conditions, with malignancies such as melanoma representing a critical diagnostic urgency. This investigation delineates the deployment of Convolutional Neural Networks (CNNs) for the classification of dermatological anomalies, benchmarking CNN diagnostic fidelity against dermatological expert evaluations. The study underscores the efficacy of CNN classifiers in expediting the diagnostic workflow for various cutaneous disorders. Advocating for an automated diagnostic framework, the research introduces a CNN-based system aimed at reducing human diagnostic load, accelerating diagnostic timelines, and enhancing survival outcomes. Utilizing advanced image processing algorithms and deep learning architectures, the research presents an automated classification system for skin pathologies, addressing both benign and malignant presentations. The classification matrix includes nine dermatological conditions: actinic keratosis, basal cell carcinoma, benign keratosis, dermatofibroma, melanoma, nevus, seborrheic keratosis, squamous cell carcinoma, and vascular lesions. The objective is to engineer a CNN model with robust diagnostic performance across a diverse lesion dataset, ensuring accurate identification and categorization of dermatological conditions.

关键词： Deep learning Pathology Accuracy Melanoma Computer architecture Benchmark testing Skin Convolutional neural networks Lesions Medical diagnosis

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Potential of fungal thermostable alpha amylase enzyme isolated from Hot springs of Central Anatolia(Turkey)in wheat bread quality

引用

Food Bioscience 2022年第1期45卷 214-222页

作者： Arzu Unal Asiye Seis Subasi Semra Malkoc Ijlal Ocak SElif Korcan Elif Yetilmezer Seyhun Yurdugül Hülya Yaman Turgay Sanal Alaettin Keceli Igdır University Faculty of AgricultureDepartment of Agricultural BiotechnologyI˘gdırTurkey Ministry of Agriculture and Forestry Field Crops Central Research Institute Department of Quality and TechnologyAnkaraTurkey Eskisehir Technical University Faculty of EngineeringDepartment of Environmental EngineeringEskisehirTurkey Afyon Kocatepe University Faculty of EducationDepartment of Mathematics and Science EducationDivision of Science EducationAfyonTurkey Usak University Vocational School of Health ServicesMedical Laboratory Techniques ProgramUsakTurkey Ministry of Agriculture and Forestry Field Crops Central Research Institute Department of BiotechnologyAnkaraTurkey Bolu Abant Izzet Baysal University Faculty of Arts and ScienceDepartment of BiologyBoluTurkey Bolu Abant Izzet Baysal University Vocational School of the Technical Sciences of BoluFood Technology ProgramBoluTurkey Pamukkale University School of Applied SciencesDepartment of Organic Farming Business ManagementDenizliTurkey

Many industrial processes may quickly proceed with biotechnological and enzymatic *** and production facilitator properties of enzymes have provided variable advantages for ***,enzyme utilization has become inevitable for industry and supplied financial advantages in case of the high energy requirement *** the study,the amylase enzymes were isolated from thermal spring sources,and the effect on bread quality was ***,fungal amylases were isolated from thermal spring sources(29-98◦C)in various places around *** determining the functional properties of amylase enzymes,the most active enzyme was used in bread production to examine their effect on bread *** maximum alpha-amylase activity(38.6 U/mg)has been detected in Aspergillus niger G 2-1 *** compared with the commercially available one,native alpha-amylase increased the bread volume.A significant difference(p<0.01)was found in the color properties and size of the bread between microbial produced in this study and commercially produced *** ppm alpha-amylase addition showed the optimum bread properties for dough processing.

关键词： Alpha-amylase Thermal spring Quality of bread Commercial enzymes

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