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Book ; Online: Continuous and Discrete LTI Systems

Mendez, Miguel A.

2022

Abstract: This chapter reviews the fundamentals of continuous and discrete Linear Time-Invariant (LTI) systems with Single Input-Single Output (SISO). We start from the general notions of signals and systems, the signal representation problem and the related ... ...

Abstract	This chapter reviews the fundamentals of continuous and discrete Linear Time-Invariant (LTI) systems with Single Input-Single Output (SISO). We start from the general notions of signals and systems, the signal representation problem and the related orthogonal bases in discrete and continuous forms. We then move to the key properties of LTI systems and discuss their eigenfunctions, the input-output relations in the time and frequency domains, the conformal mapping linking the continuous and the discrete formulations, and the modeling via differential and difference equations. Finally, we close with two important applications: (linear) models for time series analysis and forecasting and (linear) digital filters for multi-resolution analysis. This chapter contains seven exercises, the solution of which is provided in the book's webpage. Comment: Chapter 4 in the book `Data Driven Fluid Mechanics', originating from the lecture series `Machine Learning in Fluid Mechanics' organized by the von Karman Institute in 2020
Keywords	Mathematics - Optimization and Control ; Electrical Engineering and Systems Science - Signal Processing
Subject code	510
Publishing date	2022-08-25
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: A 1D model for the unsteady gas dynamics of ejectors

Berghe, Jan van den / Dias, Bruno R.B. / Bartosiewicz, Yann / Méndez, Miguel A.

Energy. 2023 Mar., v. 267 p.126551-

2023

Abstract: Ejectors are passive mixing devices that might operate in time-varying conditions, e.g., at start-up or during transients. Nevertheless, modeling efforts in literature have mostly been focused on steady conditions. In this work, we propose a novel 1D ... ...

Abstract	Ejectors are passive mixing devices that might operate in time-varying conditions, e.g., at start-up or during transients. Nevertheless, modeling efforts in literature have mostly been focused on steady conditions. In this work, we propose a novel 1D unsteady model for supersonic single-phase ejectors based on a pipeline analogy with two inlets and one outlet. Conservation of mass, momentum and energy is internally enforced in each domain through 1D gas dynamic equations, and across the domains by a junction model. The characteristics-based formulation of the junction admits a solution in the critical and the sub-critical regime, including backflow, as long as the primary nozzle is choked. Furthermore, the model is not restricted to sonic or supersonic ejectors. To the authors’ knowledge, this formulation is the first to enable 1D ejector simulations with time-varying boundary conditions across operating regimes. The model was calibrated and validated on experimental data in steady state and benchmarked against a 2D URANS simulation featuring a sudden increase in back pressure, triggering traveling pressure waves and a burst of backflow. The results show that the model can correctly predict the ejector performance and the stream-wise evolution of relevant integral quantities in both steady and transient conditions.
Keywords	energy ; evolution ; models ; momentum ; Ejector modeling ; 1D gas dynamics ; Transient entrainment
Language	English
Dates of publication	2023-03
Publishing place	Elsevier Ltd
Document type	Article ; Online
ZDB-ID	2019804-8
ISSN	0360-5442 ; 0360-5442
ISSN (online)	0360-5442
ISSN	0360-5442
DOI	10.1016/j.energy.2022.126551
Database	NAL-Catalogue (AGRICOLA)

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Article: Solid Lipid Nanoparticles Enhancing the Leishmanicidal Activity of Delamanid.

Santamaría-Aguirre, Javier / Jacho, Daniela / Méndez, Miguel A / Poveda, Ana / Carrión, Javier / Fanarraga, Mónica L

Pharmaceutics

2023 Volume 16, Issue 1

Abstract: Leishmaniasis, a zoonotic parasitic disease transmitted by infected sandflies, impacts nearly 1 million people yearly and is endemic in many countries across Asia, Africa, the Americas, and the Mediterranean; despite this, it remains a neglected disease ... ...

Abstract	Leishmaniasis, a zoonotic parasitic disease transmitted by infected sandflies, impacts nearly 1 million people yearly and is endemic in many countries across Asia, Africa, the Americas, and the Mediterranean; despite this, it remains a neglected disease with limited effective treatments, particularly in impoverished communities with limited access to healthcare. This study aims to repurpose approved drugs for an affordable leishmaniasis treatment. After the screening of potential drug candidates by reviewing databases and utilizing molecular docking analysis, delamanid was chosen to be incorporated into solid lipid nanoparticles (SLNPs). Both in cellulo and in vivo tests confirmed the successful payload release within macrophages and through the epidermis following topical application on murine skin. The evaluation of macrophages infected with
Language	English
Publishing date	2023-12-27
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2527217-2
ISSN	1999-4923
ISSN	1999-4923
DOI	10.3390/pharmaceutics16010041
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: The GA-cal software for the automatic calibration of soil constitutive laws

Mendez, Francisco J. / Mendez, Miguel A. / Pasculli, Antonio

a tutorial and a user manual

2022

Abstract: The calibration of an advanced constitutive law for soil is a challenging task. This work describes GA-cal, a Fortran software for automatically calibrating constitutive laws using Genetic Algorithms (GA) optimization. The proposed approach sets the ... ...

Abstract	The calibration of an advanced constitutive law for soil is a challenging task. This work describes GA-cal, a Fortran software for automatically calibrating constitutive laws using Genetic Algorithms (GA) optimization. The proposed approach sets the calibration problem as a regression, and the GA optimization is used to adjust the model parameters so that a numerical model matches experimental data. This document provides a user guide and a simple tutorial. We showcase GA-cal on the calibration of the Sand Hypoplastic law proposed by von Wolffersdorff, with the oedometer and triaxial drained test data. The implemented subroutines can be easily extended to solve other regression or optimization problems, including different tests and constitutive models. The source code and the presented tutorial are freely available at \url{https://github.com/FraJoMen/GA-cal}.
Keywords	Computer Science - Neural and Evolutionary Computing ; Mathematics - Optimization and Control
Subject code	600
Publishing date	2022-11-24
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Development of gelatin/carboxymethylcellulose active films containing Hass avocado peel extract and their application as a packaging for the preservation of berries

Vargas-Torrico, Maria Fernanda / Aguilar-Méndez, Miguel A. / von Borries-Medrano, Erich

International journal of biological macromolecules. 2022 Mar. 16,

2022

Abstract: This study aimed to evaluate the effect of incorporating different concentrations (0, 200, 300, and 400 mg L⁻¹) of avocado peel extracts (EE-AP) on the physicochemical properties and antifungal activity of gelatin-carboxymethylcellulose (Gel-CMC) films ... ...

Abstract	This study aimed to evaluate the effect of incorporating different concentrations (0, 200, 300, and 400 mg L⁻¹) of avocado peel extracts (EE-AP) on the physicochemical properties and antifungal activity of gelatin-carboxymethylcellulose (Gel-CMC) films and their applicability in berry preservation. The results showed that incorporating EE-AP was compatible with the Gel-CMC film and enhanced the mechanical properties without affecting the integrity and thermal properties. The 200 mg L⁻¹ of EE-AP concentration on films offered the best barrier properties against water vapor (2.90 × 10⁻¹¹ g m⁻¹ s⁻¹ Pa⁻¹). FTIR identified the intramolecular and intermolecular interactions between the functional groups of biopolymers and the EE-AP. The results obtained revealed that EE-AP incorporation into gelatin-carboxymethylcellulose films significantly decreased the moisture content (from 12.48 to 11.02%) and solubility (from 40.13 to 35.39%) of the films. All films incorporated with EE-AP showed higher colorimetric parameters and opacity than the control film (p < 0.05). The DPPH radical scavenging ability of the Gel-CMC films was increased from 24.16 to 41.12, 57.21, and 63.47%, as the extract concentration increased. Active films presented excellent ultraviolet-visible light barrier properties. The antioxidant pigments (flavonoids and chlorophylls) were estimated spectrophotometrically through absorbance. In vitro tests indicated high effectiveness to inhibit the growth of Rhizopus stolonifer and Aspergillus niger. A preservation study indicated the absence of fungal development in berries over six days of storage. In conclusion, gelatin-carboxymethylcellulose films with EE-AP represent a potential option for active packaging and can preserve fresh fruit.
Keywords	Aspergillus niger ; Rhizopus stolonifer ; absorbance ; antifungal properties ; antioxidants ; avocados ; biopolymers ; carboxymethylcellulose ; colorimetry ; flavonoids ; fungi ; gelatin ; opacity ; raw fruit ; solubility ; water content ; water vapor
Language	English
Dates of publication	2022-0316
Publishing place	Elsevier B.V.
Document type	Article
Note	Pre-press version
ZDB-ID	282732-3
ISSN	1879-0003 ; 0141-8130
ISSN (online)	1879-0003
ISSN	0141-8130
DOI	10.1016/j.ijbiomac.2022.03.101
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Development of gelatin/carboxymethylcellulose active films containing Hass avocado peel extract and their application as a packaging for the preservation of berries.

Vargas-Torrico, Maria Fernanda / von Borries-Medrano, Erich / Aguilar-Méndez, Miguel A

International journal of biological macromolecules

2022 Volume 206, Page(s) 1012–1025

Abstract: This study aimed to evaluate the effect of incorporating different concentrations (0, 200, 300, and 400 mg ... ...

Abstract	This study aimed to evaluate the effect of incorporating different concentrations (0, 200, 300, and 400 mg L
MeSH term(s)	Antioxidants/chemistry ; Antioxidants/pharmacology ; Carboxymethylcellulose Sodium/chemistry ; Food Packaging/methods ; Fruit ; Gelatin/chemistry ; Persea ; Plant Extracts/chemistry ; Plant Extracts/pharmacology
Chemical Substances	Antioxidants ; Plant Extracts ; Gelatin (9000-70-8) ; Carboxymethylcellulose Sodium (K679OBS311)
Language	English
Publishing date	2022-03-19
Publishing country	Netherlands
Document type	Journal Article
ZDB-ID	282732-3
ISSN	1879-0003 ; 0141-8130
ISSN (online)	1879-0003
ISSN	0141-8130
DOI	10.1016/j.ijbiomac.2022.03.101
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Book ; Online: Evolution of waves in liquid films on moving substrates

Ivanova, Tsvetelina / Pino, Fabio / Scheid, Benoit / Mendez, Miguel A.

2022

Abstract: Accurate and computationally accessible models of liquid film flows allow for optimizing coating processes such as hot-dip galvanization and vertical slot-die coating. This paper extends the classic three-dimensional integral boundary layer (IBL) model ... ...

Abstract	Accurate and computationally accessible models of liquid film flows allow for optimizing coating processes such as hot-dip galvanization and vertical slot-die coating. This paper extends the classic three-dimensional integral boundary layer (IBL) model for falling liquid films (FF) to account for a moving substrate (MS). We analyze the stability of the liquid films on vertically moving substrates in a linear and a nonlinear setting. In the linear analysis, we derive the dispersion relation and the temporal growth rates of an infinitesimal disturbance using normal modes and linearized governing equations. In the nonlinear analysis, we consider disturbances of finite size and numerically compute their evolution using the set of nonlinear equations in which surface tension has been removed. We present the region of (linear) stability of both FF and MS configurations, and we place the operating conditions of an industrial galvanizing line in these maps. A wide range of flow conditions was analyzed and shown to be stable according to linear and nonlinear stability analyses. Moreover, the nonlinear analysis, carried out in the absence of surface tension, reveals a nonlinear stabilizing mechanism for the interface dynamics of a liquid film dragged by an upward-moving substrate.
Keywords	Physics - Fluid Dynamics
Subject code	621
Publishing date	2022-03-15
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: A Robust Data-Driven Model for Flapping Aerodynamics under different hovering kinematics

Calado, Andre / Poletti, Romain / Koloszar, Lilla K. / Mendez, Miguel A.

2022

Abstract: Flapping Wing Micro Air Vehicles (FWMAV) are highly manoeuvrable, bio-inspired drones that can assist in surveys and rescue missions. Flapping wings generate various unsteady lift enhancement mechanisms challenging the derivation of reduced models to ... ...

Abstract	Flapping Wing Micro Air Vehicles (FWMAV) are highly manoeuvrable, bio-inspired drones that can assist in surveys and rescue missions. Flapping wings generate various unsteady lift enhancement mechanisms challenging the derivation of reduced models to predict instantaneous aerodynamic performance. In this work, we propose a robust CFD data-driven, quasi-steady (QS) Reduced Order Model (ROM) to predict the lift and drag coefficients within a flapping cycle. The model is derived for a rigid ellipsoid wing with different parameterized kinematics in hovering conditions. The proposed ROM is built via a two-stage regression. The first stage, defined as `in-cycle' (IC), computes the parameters of a regression linking the aerodynamic coefficients to the instantaneous wing state. The second stage, `out-of-cycle' (OOC), links the IC weights to the flapping features that define the flapping motion. The training and test dataset were generated via high-fidelity simulations using the overset method, spanning a wide range of Reynolds numbers and flapping kinematics. The two-stage regressor combines Ridge regression and Gaussian Process (GP) regression to provide estimates of the model uncertainties. The proposed ROM shows accurate aerodynamic predictions for widely varying kinematics. The model performs best for smooth kinematics that generate a stable Leading Edge Vortex (LEV). Remarkably accurate predictions are also observed in dynamic scenarios where the LEV is partially shed, the non-circulatory forces are considerable, and the wing encounters its own wake. Comment: submitted to Physics of Fluids
Keywords	Physics - Fluid Dynamics
Subject code	612
Publishing date	2022-12-19
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Development of gelatin-carboxymethylcellulose coatings incorporated with avocado epicarp and coconut endocarp extracts to control fungal growth in strawberries for shelf-life extension

Vargas-Torrico, Maria Fernanda / von Borries-Medrano, Erich / Valle Guadarrama, Salvador / Aguilar-Méndez, Miguel A.

CyTA - Journal of Food. 2022 Dec. 31, v. 20, no. 1 p.27-38

2022

Abstract: The objective of this study was to incorporate avocado peel (AEE) and coconut (CEE) extracts as antifungal additive in the development of gelatin and carboxymethylcellulose coatings to extend shelf life in strawberries. Fractions of 200 mg/L of extracts ... ...

Title translation	Desarrollo de recubrimientos de gelatina-carboximetilcelulosa incorporados con extractos de epicarpio de aguacate y endocarpio de coco para controlar el crecimiento de hongos en fresas y extender su vida de anaquel
Abstract	The objective of this study was to incorporate avocado peel (AEE) and coconut (CEE) extracts as antifungal additive in the development of gelatin and carboxymethylcellulose coatings to extend shelf life in strawberries. Fractions of 200 mg/L of extracts were incorporated in the coating and characterized during storage at 2°C. AEE and CEE in the coating delayed significantly (P < .05) weight loss (40%), softening, color, and compositional changes (°Brix, sugars, titratable acidity). Rhizopus stolonifer and Aspergillus niger strains were isolated and inoculated to evaluate the effectiveness of the coatings on strawberries. The use of the coating + plant extracts decreased the proliferation of fungi by 45% compared to the uncoated fruit and extended the shelf life for 15 days. With these findings, it is suggested that biopolymeric coatings + plant extracts can be used as a potential method of ecological preservation in strawberries against microbial deterioration.
Keywords	Aspergillus niger ; Rhizopus stolonifer ; avocados ; carboxymethylcellulose ; coconuts ; color ; endocarp ; exocarp ; fungal growth ; gelatin ; shelf life ; titratable acidity ; weight loss ; Strawberries ; fungal control ; plant extract ; postharvest shelf life ; edible coatings
Language	English
Dates of publication	2022-1231
Size	p. 27-38.
Publishing place	Taylor & Francis
Document type	Article ; Online
ZDB-ID	2515457-6
ISSN	1947-6345
ISSN	1947-6345
DOI	10.1080/19476337.2021.2024607
Database	NAL-Catalogue (AGRICOLA)

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Book ; Online: On the Dynamics of the Jet Wiping Process

Barreiro-Villaverde, David / Gosset, Anne / Mendez, Miguel A.

Numerical Simulations and Modal Analysis

2021

Abstract: We analyze the flow of a planar gas jet impinging on a thin film, dragged by a vertical moving wall. In the coating industry, this configuration is known as jet wiping, a process in which impinging jets control the thickness of liquid coatings on flat ... ...

Abstract	We analyze the flow of a planar gas jet impinging on a thin film, dragged by a vertical moving wall. In the coating industry, this configuration is known as jet wiping, a process in which impinging jets control the thickness of liquid coatings on flat plates withdrawn vertically from a coating bath. We present three-dimensional (3D) two-phase flow simulations combining Large Eddy Simulation (LES) and Volume of Fluid (VOF). Three wiping configurations are simulated and the results are validated with experimental data from previous works. Multiscale modal analysis is used to analyze the dynamic interaction between the gas flow and the liquid film. In particular, we present a combination of Multiscale Proper Orthogonal decomposition (mPOD) and correlation analysis. The mPOD is used to identify the dominant travelling wave pattern in the liquid film flow, and the temporal structures are used to determine the most correlated flow features in the gas jet. This allows for revealing a two-dimensional (2D) mechanism for wave formation in the liquid coat. Finally, we use the numerical results to analyze the validity of some of the critical assumptions underpinning the derivation of integral film models of jet wiping. Comment: submitted to Physics of Fluids
Keywords	Physics - Fluid Dynamics
Subject code	621 ; 532
Publishing date	2021-03-30
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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