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Wilkins Aquino

Professor in the Thomas Lord Department of Mechanical Engineering and Materials Science
Thomas Lord Department of Mechanical Engineering and Materials Science
121 Hudson Hall, Box 90287, Durham, NC 27708
309 Gross Hall, Durham, NC 27708

Selected Publications


Assessing decision boundaries under uncertainty

Journal Article Structural and Multidisciplinary Optimization · July 1, 2024 In order to make design decisions, engineers may seek to identify regions of the design domain that are acceptable in a computationally efficient manner. A design is typically considered acceptable if its reliability with respect to parametric uncertainty ... Full text Cite

Active design of diffuse acoustic fields in enclosures.

Journal Article The Journal of the Acoustical Society of America · February 2024 This paper presents a numerical framework for designing diffuse fields in rooms of any shape and size, driven at arbitrary frequencies. That is, we aim at overcoming the Schroeder frequency limit for generating diffuse fields in an enclosed space. We formu ... Full text Cite

Generalized Bayes approach to inverse problems with model misspecification.

Journal Article Inverse problems · October 2023 We propose a general framework for obtaining probabilistic solutions to PDE-based inverse problems. Bayesian methods are attractive for uncertainty quantification but assume knowledge of the likelihood model or data generation process. This assumption is d ... Full text Cite

Bayesian Optimal Sensor Placement for Damage Detection in Frequency-Domain Dynamics

Journal Article Journal of Engineering Mechanics · December 1, 2022 Identification and monitoring of structural damage have a growing importance in the maintenance of aging structures. Specifically, an optimal sensor configuration capable of fully identifying structural damage is desired. One innovative approach is casting ... Full text Cite

A Locally Adapted Reduced-Basis Method for Solving Risk-Averse PDE-Constrained Optimization Problems

Journal Article SIAM-ASA Journal on Uncertainty Quantification · December 1, 2022 The numerical solution of risk-averse optimization problems constrained by PDEs requires substantial computational effort resulting from the discretization of the underlying PDE in both the physical and stochastic dimensions. To practically solve these cha ... Full text Cite

Optimization of Acoustic Channels to Minimize Scattered Pressure Fields

Journal Article Journal of Theoretical and Computational Acoustics · September 1, 2022 Acoustic and elastic metamaterials have shown potential for many different applications in wave manipulation and structural isolation. Minimization of a scattered wave field has been identified as an important use for such materials, and a wide variety of ... Full text Cite

The influence of acoustic radiation force beam shape and location on wave spectral content for arterial dispersion ultrasound vibrometry.

Journal Article Physics in medicine and biology · June 2022 Objective. Arterial dispersion ultrasound vibrometry (ADUV) relies on the use of guided waves in arterial geometries for shear wave elastography measurements. Both the generation of waves through the use of acoustic radiation force (ARF) and the tec ... Full text Cite

Machine Learning for Urodynamic Detection of Detrusor Overactivity.

Journal Article Urology · January 2022 OBJECTIVE: To develop a machine learning algorithm that identifies detrusor overactivity (DO) in Urodynamic Studies (UDS) in the spina bifida population. UDS plays a key role in assessment of neurogenic bladder in patients with spina bifida. Due to signifi ... Full text Link to item Cite

An adaptive eigenfunction basis strategy to reduce design dimension in topology optimization

Journal Article International Journal for Numerical Methods in Engineering · December 30, 2021 The concept of adaptive eigenspace basis (AEB) has recently proved effective for solving medium imaging problems. In this article, we present an AEB strategy for design parameterization in topology optimization (TO) problems. We seek the density design fie ... Full text Cite

Toward improved accuracy in shear wave elastography of arteries through controlling the arterial response to ultrasound perturbation in-silico and in phantoms.

Journal Article Physics in medicine and biology · November 2021 Dispersion-based inversion has been proposed as a viable direction for materials characterization of arteries, allowing clinicians to better study cardiovascular conditions using shear wave elastography. However, these methods rely ona prioriknowled ... Full text Cite

Plane wave elastography: a frequency-domain ultrasound shear wave elastography approach.

Journal Article Physics in medicine and biology · June 2021 In this paper, we propose plane wave elastography (PWE), a novel ultrasound shear wave elastography (SWE) approach. Currently, commercial methods for SWE rely on directional filtering based on the prior knowledge of the wave propagation direction, to remov ... Full text Cite

Novel strategies for modal-based structural material identification

Journal Article Mechanical Systems and Signal Processing · February 15, 2021 In this work, we present modal-based methods for model calibration in structural dynamics, and address several key challenges in the solution of gradient-based optimization problems with eigenvalues and eigenvectors, including the solution of singular Helm ... Full text Cite

An error-in-constitutive equations strategy for topology optimization for frequency-domain dynamics

Journal Article Computer Methods in Applied Mechanics and Engineering · December 1, 2020 This paper presents a topology optimization formulation for frequency-domain dynamics to reduce solution dependence upon initial guess and considered loading conditions. Due to resonance phenomena in undamped steady-state dynamics, objectives measuring dyn ... Full text Cite

Ultrasound elastography using a regularized modified error in constitutive equations (MECE) approach: a comprehensive phantom study.

Journal Article Physics in medicine and biology · November 2020 Many of the current techniques in transient elastography, such as shear wave elastography (SWE) assume a dominant planar shear wave propagating in an infinite medium. This underlying assumption, however, can be easily violated in real scenarios in vivo, le ... Full text Cite

A Generalized Stress Inversion Approach with Application to Residual Stress Estimation

Journal Article Journal of Applied Mechanics, Transactions ASME · November 1, 2020 We develop a generalized stress inversion technique (or the generalized inversion method) capable of recovering stresses in linear elastic bodies subjected to arbitrary cuts. Specifically, given a set of displacement measurements found experimentally from ... Full text Cite

Sensor Planning for Model-Based Acoustic Source Identification

Conference Proceedings of the American Control Conference · July 1, 2020 In this paper we propose an online active sensor planning strategy for model-based acoustic source identification (SI) in non-convex domains utilizing the three-dimensional Helmholtz partial differential equation (PDE). After discretizing the PDE using the ... Full text Cite

Model-Based Active Source Identification in Complex Environments

Journal Article IEEE Transactions on Robotics · June 1, 2019 In this paper, we consider the problem of Active Source Identification in steady-state advection-diffusion (AD) transport systems. Unlike existing bioinspired heuristic methods, we propose a model-based approach that employs the AD-partial differential equ ... Full text Cite

An adaptive local reduced basis method for solving PDEs with uncertain inputs and evaluating risk

Journal Article Computer Methods in Applied Mechanics and Engineering · March 1, 2019 Many physical systems are modeled using partial differential equations (PDEs) with uncertain or random inputs. For such systems, naively propagating a fixed number of samples of the input probability law (or an approximation thereof) through the PDE is oft ... Full text Cite

A gradient-based optimization approach for the detection of partially connected surfaces using vibration tests

Journal Article Computer Methods in Applied Mechanics and Engineering · March 1, 2019 The integrity of engineering structures is often compromised by embedded surfaces that result from incomplete bonding during the manufacturing process, or initiation of damage from fatigue or impact processes. Examples include delaminations in composite ma ... Full text Cite

Inverse methods for characterization of contact areas in mechanical systems

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2019 In computational structural dynamics problems, the ability to calibrate numerical models to physical test data often depends on determining the correct constraints within a structure with mechanical interfaces. These interfaces are defined as the locations ... Full text Cite

Assessing decision boundaries under uncertainty

Journal Article Structural and Multidisciplinary Optimization · July 1, 2024 In order to make design decisions, engineers may seek to identify regions of the design domain that are acceptable in a computationally efficient manner. A design is typically considered acceptable if its reliability with respect to parametric uncertainty ... Full text Cite

Active design of diffuse acoustic fields in enclosures.

Journal Article The Journal of the Acoustical Society of America · February 2024 This paper presents a numerical framework for designing diffuse fields in rooms of any shape and size, driven at arbitrary frequencies. That is, we aim at overcoming the Schroeder frequency limit for generating diffuse fields in an enclosed space. We formu ... Full text Cite

Generalized Bayes approach to inverse problems with model misspecification.

Journal Article Inverse problems · October 2023 We propose a general framework for obtaining probabilistic solutions to PDE-based inverse problems. Bayesian methods are attractive for uncertainty quantification but assume knowledge of the likelihood model or data generation process. This assumption is d ... Full text Cite

Bayesian Optimal Sensor Placement for Damage Detection in Frequency-Domain Dynamics

Journal Article Journal of Engineering Mechanics · December 1, 2022 Identification and monitoring of structural damage have a growing importance in the maintenance of aging structures. Specifically, an optimal sensor configuration capable of fully identifying structural damage is desired. One innovative approach is casting ... Full text Cite

A Locally Adapted Reduced-Basis Method for Solving Risk-Averse PDE-Constrained Optimization Problems

Journal Article SIAM-ASA Journal on Uncertainty Quantification · December 1, 2022 The numerical solution of risk-averse optimization problems constrained by PDEs requires substantial computational effort resulting from the discretization of the underlying PDE in both the physical and stochastic dimensions. To practically solve these cha ... Full text Cite

Optimization of Acoustic Channels to Minimize Scattered Pressure Fields

Journal Article Journal of Theoretical and Computational Acoustics · September 1, 2022 Acoustic and elastic metamaterials have shown potential for many different applications in wave manipulation and structural isolation. Minimization of a scattered wave field has been identified as an important use for such materials, and a wide variety of ... Full text Cite

The influence of acoustic radiation force beam shape and location on wave spectral content for arterial dispersion ultrasound vibrometry.

Journal Article Physics in medicine and biology · June 2022 Objective. Arterial dispersion ultrasound vibrometry (ADUV) relies on the use of guided waves in arterial geometries for shear wave elastography measurements. Both the generation of waves through the use of acoustic radiation force (ARF) and the tec ... Full text Cite

Machine Learning for Urodynamic Detection of Detrusor Overactivity.

Journal Article Urology · January 2022 OBJECTIVE: To develop a machine learning algorithm that identifies detrusor overactivity (DO) in Urodynamic Studies (UDS) in the spina bifida population. UDS plays a key role in assessment of neurogenic bladder in patients with spina bifida. Due to signifi ... Full text Link to item Cite

An adaptive eigenfunction basis strategy to reduce design dimension in topology optimization

Journal Article International Journal for Numerical Methods in Engineering · December 30, 2021 The concept of adaptive eigenspace basis (AEB) has recently proved effective for solving medium imaging problems. In this article, we present an AEB strategy for design parameterization in topology optimization (TO) problems. We seek the density design fie ... Full text Cite

Toward improved accuracy in shear wave elastography of arteries through controlling the arterial response to ultrasound perturbation in-silico and in phantoms.

Journal Article Physics in medicine and biology · November 2021 Dispersion-based inversion has been proposed as a viable direction for materials characterization of arteries, allowing clinicians to better study cardiovascular conditions using shear wave elastography. However, these methods rely ona prioriknowled ... Full text Cite

Plane wave elastography: a frequency-domain ultrasound shear wave elastography approach.

Journal Article Physics in medicine and biology · June 2021 In this paper, we propose plane wave elastography (PWE), a novel ultrasound shear wave elastography (SWE) approach. Currently, commercial methods for SWE rely on directional filtering based on the prior knowledge of the wave propagation direction, to remov ... Full text Cite

Novel strategies for modal-based structural material identification

Journal Article Mechanical Systems and Signal Processing · February 15, 2021 In this work, we present modal-based methods for model calibration in structural dynamics, and address several key challenges in the solution of gradient-based optimization problems with eigenvalues and eigenvectors, including the solution of singular Helm ... Full text Cite

An error-in-constitutive equations strategy for topology optimization for frequency-domain dynamics

Journal Article Computer Methods in Applied Mechanics and Engineering · December 1, 2020 This paper presents a topology optimization formulation for frequency-domain dynamics to reduce solution dependence upon initial guess and considered loading conditions. Due to resonance phenomena in undamped steady-state dynamics, objectives measuring dyn ... Full text Cite

Ultrasound elastography using a regularized modified error in constitutive equations (MECE) approach: a comprehensive phantom study.

Journal Article Physics in medicine and biology · November 2020 Many of the current techniques in transient elastography, such as shear wave elastography (SWE) assume a dominant planar shear wave propagating in an infinite medium. This underlying assumption, however, can be easily violated in real scenarios in vivo, le ... Full text Cite

A Generalized Stress Inversion Approach with Application to Residual Stress Estimation

Journal Article Journal of Applied Mechanics, Transactions ASME · November 1, 2020 We develop a generalized stress inversion technique (or the generalized inversion method) capable of recovering stresses in linear elastic bodies subjected to arbitrary cuts. Specifically, given a set of displacement measurements found experimentally from ... Full text Cite

Sensor Planning for Model-Based Acoustic Source Identification

Conference Proceedings of the American Control Conference · July 1, 2020 In this paper we propose an online active sensor planning strategy for model-based acoustic source identification (SI) in non-convex domains utilizing the three-dimensional Helmholtz partial differential equation (PDE). After discretizing the PDE using the ... Full text Cite

Model-Based Active Source Identification in Complex Environments

Journal Article IEEE Transactions on Robotics · June 1, 2019 In this paper, we consider the problem of Active Source Identification in steady-state advection-diffusion (AD) transport systems. Unlike existing bioinspired heuristic methods, we propose a model-based approach that employs the AD-partial differential equ ... Full text Cite

An adaptive local reduced basis method for solving PDEs with uncertain inputs and evaluating risk

Journal Article Computer Methods in Applied Mechanics and Engineering · March 1, 2019 Many physical systems are modeled using partial differential equations (PDEs) with uncertain or random inputs. For such systems, naively propagating a fixed number of samples of the input probability law (or an approximation thereof) through the PDE is oft ... Full text Cite

A gradient-based optimization approach for the detection of partially connected surfaces using vibration tests

Journal Article Computer Methods in Applied Mechanics and Engineering · March 1, 2019 The integrity of engineering structures is often compromised by embedded surfaces that result from incomplete bonding during the manufacturing process, or initiation of damage from fatigue or impact processes. Examples include delaminations in composite ma ... Full text Cite

Inverse methods for characterization of contact areas in mechanical systems

Conference Conference Proceedings of the Society for Experimental Mechanics Series · January 1, 2019 In computational structural dynamics problems, the ability to calibrate numerical models to physical test data often depends on determining the correct constraints within a structure with mechanical interfaces. These interfaces are defined as the locations ... Full text Cite

Analysis of the error in constitutive equation approach for time-harmonic elasticity imaging

Journal Article SIAM Journal on Applied Mathematics · January 1, 2019 We consider the identification of heterogeneous linear elastic moduli in the context of time-harmonic elastodynamics. This inverse problem is formulated as the minimization of the modified error in constitutive equation (MECE), an energy-based cost functio ... Full text Cite

Distributed Reduced Order Source Identification

Conference Proceedings of the American Control Conference · August 9, 2018 In this paper we propose a distributed approach for model-based Source Identification (SI) that minimizes communication cost and allows for on demand balancing of computational resources, based on the specifications of the sensors. Specifically, we conside ... Full text Cite

Physics-Based Acoustic Source Identification

Conference Proceedings of the IEEE Conference on Decision and Control · July 2, 2018 In this paper we propose an acoustic source identification algorithm to localize multiple sources in non-trivial domains. We capture the physics of the acoustic wave propagation via the Helmholtz partial differential equation. Given a set of noisy complex ... Full text Cite

Design of continuously graded elastic acoustic cloaks.

Journal Article The Journal of the Acoustical Society of America · January 2018 This letter demonstrates the design of continuously graded elastic cylinders to achieve passive cloaking from harmonic acoustic excitation, both at single frequencies and over extended bandwidths. The constitutive parameters in a multilayered, constant-den ... Full text Cite

A locally adapted reduced basis method for solving risk-averse pde-constrained optimization problems

Conference AIAA Non-Deterministic Approaches Conference, 2018 · January 1, 2018 The numerical solution of risk-averse PDE-constrained optimization problems requires substantial computational effort resulting from the discretization of the underlying PDE in both the physical and stochastic dimensions. To practically solve problems with ... Full text Cite

Notice of Removal: Measurement of carotid artery viscoelasticity in young and older individuals using acoustic radiation force-induced waves and Fourier analysis

Conference IEEE International Ultrasonics Symposium, IUS · October 31, 2017 Techniques that can quantitatively measure viscoelastic mechanical properties in arteries may be very useful to detect early disease processes. We propose the use of inducing waves in the arterial walls with acoustic radiation force (ARF) and measuring the ... Full text Cite

Modified error in constitutive equations (MECE) approach for ultrasound elastography.

Journal Article The Journal of the Acoustical Society of America · October 2017 A partial differential equation-constrained optimization approach is presented for reconstructing mechanical properties (e.g., elastic moduli). The proposed method is based on the minimization of an error in constitutive equations functional augmented with ... Full text Cite

Arterial waveguide model for shear wave elastography: implementation and in vitro validation.

Journal Article Physics in medicine and biology · July 2017 Arterial stiffness is found to be an early indicator of many cardiovascular diseases. Among various techniques, shear wave elastography has emerged as a promising tool for estimating local arterial stiffness through the observed dispersion of guided waves. ... Full text Cite

Stochastic model-based source identification

Conference 2017 IEEE 56th Annual Conference on Decision and Control, CDC 2017 · June 28, 2017 In this paper we investigate the use of Stochastic Reduced Order Models (SROMs) for solving Stochastic Source Identification (SSI) problems in steady-state transport phenomena given statistics of the system state at a small number of locations. We capture ... Full text Cite

Nitsche's Method For Helmholtz Problems with Embedded Interfaces.

Journal Article International journal for numerical methods in engineering · May 2017 In this work, we use Nitsche's formulation to weakly enforce kinematic constraints at an embedded interface in Helmholtz problems. Allowing embedded interfaces in a mesh provides significant ease for discretization, especially when material interfaces have ... Full text Cite

An adaptive sampling approach for solving PDEs with uncertain inputs and evaluating risk

Conference 19th AIAA Non-Deterministic Approaches Conference, 2017 · January 1, 2017 © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. When solving partial differential equations (PDEs) with random inputs, it is often computationally inefficient to merely propagate samples of the input probability l ... Cite

An adaptive sampling approach for solving PDEs with uncertain inputs and evaluating risk

Conference 19th AIAA Non-Deterministic Approaches Conference, 2017 · January 1, 2017 When solving partial differential equations (PDEs) with random inputs, it is often computationally inefficient to merely propagate samples of the input probability law (or an approximation thereof) because the input law may not accurately capture the behav ... Full text Cite

Measured wave dispersion in tubes excited with acoustic radiation force matches theoretical guided wave dispersion

Conference IEEE International Ultrasonics Symposium, IUS · November 1, 2016 Acoustic radiation force (ARF) has been used to generate shear waves in many different tissues for the purpose of quantifying material properties of those tissues. This method has also been applied to arteries, but care must be taken in this application be ... Full text Cite

Multi-model polynomial chaos surrogate dictionary for Bayesian inference in elasticity problems

Journal Article Probabilistic Engineering Mechanics · October 1, 2016 A method is presented for inferring the presence of an inclusion inside a domain; the proposed approach is suitable to be used in a diagnostic device with low computational power. Specifically, we use the Bayesian framework for the inference of stiff inclu ... Full text Cite

Nonlinear reduced order source identification

Conference Proceedings of the American Control Conference · July 28, 2016 In this paper we propose a novel approach to the problem of model-based source identification in steady-state transport phenomena given a set of noisy measurements. We formulate the problem as an optimization problem in function space and utilize the adjoi ... Full text Cite

A Modified Error in Constitutive Equation Approach for Frequency-Domain Viscoelasticity Imaging Using Interior Data.

Journal Article Computer methods in applied mechanics and engineering · November 2015 This paper presents a methodology for the inverse identification of linearly viscoelastic material parameters in the context of steady-state dynamics using interior data. The inverse problem of viscoelasticity imaging is solved by minimizing a modified err ... Full text Cite

Model-based sparse source identification

Conference Proceedings of the American Control Conference · July 28, 2015 This paper presents a model-based approach for source identification using sparse recovery techniques. In particular, given an arbitrary domain that contains a set of unknown sources and a set of stationary sensors that can measure a quantity generated by ... Full text Cite

Simultaneous identification of elastic properties, thickness, and diameter of arteries excited with ultrasound radiation force.

Journal Article Physics in medicine and biology · July 2015 The elastic and geometric properties of arteries have been long recognized as important predictors of cardiovascular disease. This work presents a robust technique for the noninvasive characterization of anisotropic elastic properties as well as thickness ... Full text Cite

Stochastic reduced order models for inverse problems under uncertainty.

Journal Article Computer methods in applied mechanics and engineering · March 2015 This work presents a novel methodology for solving inverse problems under uncertainty using stochastic reduced order models (SROMs). Given statistical information about an observed state variable in a system, unknown parameters are estimated probabilistica ... Full text Cite

Three-dimensional transient elastodynamic inversion using an error in constitutive relation functional

Journal Article Inverse Problems · March 1, 2015 This work is concerned with large-scale three-dimensional (3D) inversion under transient elastodynamic conditions by means of the modified error in constitutive relation (MECR), an energy-based, cost functional. In contrast to quasi-static or frequency-dom ... Full text Cite

Inverse Material Identification in Coupled Acoustic-Structure Interaction using a Modified Error in Constitutive Equation Functional.

Journal Article Computational mechanics · September 2014 This work focuses on the identification of heterogeneous linear elastic moduli in the context of frequency-domain, coupled acoustic-structure interaction (ASI), using either solid displacement or fluid pressure measurement data. The approach postulates the ... Full text Cite

A multiscale mass scaling approach for explicit time integration using proper orthogonal decomposition

Journal Article International Journal for Numerical Methods in Engineering · March 16, 2014 One of the main computational issues with explicit dynamics simulations is the significant reduction of the critical time step as the spatial resolution of the finite element mesh increases. In this work, a selective mass scaling approach is presented that ... Full text Cite

Stochastic reduced order models for uncertainty quantification of intergranular corrosion rates

Journal Article Corrosion Science · March 1, 2014 We present a stochastic reduced order model (SROM) approach for quantifying uncertainty in systems undergoing corrosion. A SROM is a simple random element with a small number of samples that approximates the statistics of another target random element. The ... Full text Cite

Three-dimensional transient elastodynamic inversion using the modified error in constitutive relation

Conference Journal of Physics: Conference Series · January 1, 2014 This work is concerned with large-scale three-dimensional inversion under transient elastodynamic conditions by means of the modified error in constitutive relation (MECR), an energy-based cost functional. A peculiarity of time-domain MECR formulations is ... Full text Cite

Changes in electrodic reaction rates due to elastic stress and stress-induced surface patterns

Journal Article Electrochimica Acta · September 23, 2013 This paper investigates the influence of elastic stresses and surface patterns on electrodic reaction rates. There are several well known processes that affect electrodic reaction rates such as rupture of passive layers, repassivation, and hydrogen adsopti ... Full text Cite

A source sensitivity approach for source localization in steady-state linear systems

Journal Article Inverse Problems · September 1, 2013 Localizing sources in physical systems represents a class of inverse problems with broad scientific and engineering applications. This paper is concerned with the development of a non-iterative source sensitivity approach for the localization of sources in ... Full text Cite

Large Scale Parameter Estimation Problems in Frequency-Domain Elastodynamics Using an Error in Constitutive Equation Functional.

Journal Article Computer methods in applied mechanics and engineering · January 2013 This paper presents the formulation and implementation of an Error in Constitutive Equations (ECE) method suitable for large-scale inverse identification of linear elastic material properties in the context of steady-state elastodynamics. In ECE-based meth ... Full text Cite

Stochastic reduced order models for random vectors: Application to random eigenvalue problems

Journal Article Probabilistic Engineering Mechanics · January 1, 2013 An improved optimization algorithm is presented to construct accurate reduced order models for random vectors. The stochastic reduced order models (SROMs) are simple random elements that have a finite number of outcomes of unequal probabilities. The defini ... Full text Cite

A numerical framework for the modeling of corrosive dissolution

Journal Article Corrosion Science · December 1, 2012 We present in this work a numerical framework for simulating corrosive dissolution over long periods of time. Our proposed framework consists of three main elements: a novel dilute electrochemical model, a projective integration approach for obtaining the ... Full text Cite

A review of vibro-acoustography and its applications in medicine

Journal Article Current Medical Imaging Reviews · November 1, 2011 In recent years, several new techniques based on the radiation force of ultrasound have been developed. Vibroacoustography is a speckle-free ultrasound based imaging modality that can visualize normal and abnormal soft tissue through mapping the acoustic r ... Full text Cite

Electroneutrality and ionic interactions in the modeling of mass transport in dilute electrochemical systems

Journal Article Electrochimica Acta · October 1, 2011 We propose a simple, but novel mathematical and numerical approach to describe mass transport in dilute solutions, taking into consideration ionic interactions. Our proposed approach treats fluxes due to ionic interactions as additional unknowns in the tra ... Full text Cite

Measurement of biaxial mechanical properties of soft tubes and arteries using piezoelectric elements and sonometry.

Journal Article Physics in medicine and biology · June 2011 Arterial elasticity has gained importance in recent decades because it has been shown to be an independent predictor of cardiovascular diseases. Several in vivo and ex vivo techniques have been developed to characterize the elastic properties of vessels. I ... Full text Cite

A spectral finite element approach to modeling soft solids excited with high-frequency harmonic loads

Journal Article Computer Methods in Applied Mechanics and Engineering · January 15, 2011 An approach for efficient and accurate finite element analysis of harmonically excited soft solids using high-order spectral finite elements is presented and evaluated. The Helmholtz-type equations used to model such systems suffer from additional numerica ... Full text Cite

Inverse identification of viscoelastic material properties using an error in constitutive equations approach

Conference Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011 · January 1, 2011 This work presents a methodology based on the concept of error in constitutive equations for the inverse reconstruction of viscoelastic properties using steady-state dynamics. The ECE algorithm presented herein consists of two main steps. In the first step ... Cite

An inverse problem approach for elasticity imaging through vibroacoustics.

Journal Article IEEE transactions on medical imaging · April 2010 A methodology for estimating the spatial distribution of elastic moduli using the steady-state dynamic response of solids immersed in fluids is presented. The technique relies on the ensuing acoustic field from a remotely excited solid to inversely estimat ... Full text Cite

Thermal safety of vibro-acoustography using a confocal transducer.

Journal Article Ultrasound in medicine & biology · February 2010 Vibro-acoustography (VA) is an imaging method that forms a two-dimensional (2-D) image by moving two cofocused ultrasound beams with slightly different frequencies over the object in a C-scan format and recording acoustic emission from the focal region at ... Full text Cite

A method for combining experimentation and molecular dynamics simulation to improve cohesive zone models for metallic microstructures

Journal Article 12th International Conference on Fracture 2009, ICF-12 · December 1, 2009 Fracture processes within a material begin at the nanometer length scale at which the formation, propagation, and interaction of fundamental damage mechanisms occur. Physics-based modeling of these atomic processes quickly becomes computationally intractab ... Cite

Generalized finite element method using proper orthogonal decomposition

Journal Article International Journal for Numerical Methods in Engineering · August 13, 2009 A methodology is presented for generating enrichment functions in generalized finite element methods (GFEM) using experimental and/or simulated data. The approach is based on the proper orthogonal decomposition (POD) technique, which is used to generate lo ... Full text Cite

Inverse viscoelastic material characterization using POD reduced-order modeling in acoustic-structure interaction

Journal Article Computer Methods in Applied Mechanics and Engineering · February 15, 2009 A strategy is presented for applying the proper orthogonal decomposition (POD) technique for model reduction in computational inverse solution strategies for viscoelastic material characterization. POD is used to derive a basis of optimal dimension from a ... Full text Cite

A computational framework to model damage due to corrosion in aluminum alloys

Journal Article Structural Health Monitoring 2009: From System Integration to Autonomous Systems - Proceedings of the 7th International Workshop on Structural Health Monitoring, IWSHM 2009 · January 1, 2009 The objective of this work is to develop a simulation environment to study corrosion induced damage in aluminum alloys. The computational framework includes coupling of electrostatics and stress evolution processes. The rate of corrosion is obtained by sol ... Cite

Evaluation of biaxial mechanical properties of soft tubes and arteries using sonometry.

Journal Article Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference · January 2009 Arterial elasticity has become a topic of importance in the past decades, as it has shown that it can be used to predict cardiovascular diseases and mortality. Several in vivo and ex vivo techniques have been developed to characterize the mechanical proper ... Full text Cite

A posteriori initial imperfection identification in shell buckling problems

Journal Article Computer Methods in Applied Mechanics and Engineering · December 1, 2008 The current research seeks to demonstrate that an inverse solution approach, leveraging nonlinear finite element analysis with a divide and conquer type stochastic search algorithm, can identify the presence of localized denting imperfections in cylindrica ... Full text Cite

Identification of material properties of orthotropic elastic cylinders immersed in fluid using vibroacoustic techniques.

Journal Article Ultrasonics · November 2008 A numerical study is presented to show the potential for using vibroacoustic-based experiments to identify elastic material properties of orthotropic cylindrical vessels immersed in fluids. Sensitivity analyses and a simulated inverse problem are shown to ... Full text Cite

Structural damage identification using co-evolution and frequency response functions

Journal Article Structural Control and Health Monitoring · March 1, 2008 A new damage identification strategy is presented in which damage scenarios and optimal tests are searched simultaneously. The proposed strategy, called Estimation-Exploration Algorithm (EEA), is based on co-evolutionary principles. Co-evolution is a biolo ... Full text Cite

Simultaneous inverse identification of transient thermal properties and heat sources using sparse sensor information

Journal Article JOURNAL OF ENGINEERING MECHANICS-ASCE · December 2007 A study is presented herein on the simultaneous inverse identification of transient internal heat generation, transient thermal diffusivity, and constant convection coefficients. The formulations of the direct and inverse problems are presented in the cont ... Full text Cite

Surrogate-Model Accelerated Random Search algorithm for global optimization with applications to inverse material identification

Journal Article Computer Methods in Applied Mechanics and Engineering · September 15, 2007 An optimization algorithm is proposed which is applicable for the global optimization of computationally expensive functions with specific applications in material identification. The methodology, referred to as the Surrogate-Model Accelerated Random Searc ... Full text Cite

An object-oriented framework for reduced-order models using proper orthogonal decomposition (POD)

Journal Article Computer Methods in Applied Mechanics and Engineering · September 1, 2007 This work presents an object-oriented design for reduced-order modeling using the proper orthogonal decomposition (POD) technique. Object-oriented design attributes such as data encapsulation, inheritance, and polymorphism are shown to produce efficient im ... Full text Cite

A method for measuring transient thermal diffusivity in hydrating Portland cement mortars using an oscillating boundary temperature

Journal Article Cement and Concrete Research · May 1, 2007 The transient thermal diffusivity in early-age, type I Portland cement mortars is difficult to quantify because the exothermic reactions cause significant heat generation which complicates the analysis of heat transfer. This paper outlines the theory and s ... Full text Cite

Seismic retrofitting of corroded reinforced concrete columns using carbon composites

Journal Article ACI Structural Journal · May 1, 2007 This laboratory study concerns the use of carbon composites to restore the seismic effectiveness of corrosion-damaged reinforced concrete bridge columns with inadequate length lap-spliced reinforcement at their base and subjected to severe environmental co ... Cite

Inverse estimation of viscoelastic material properties for solids immersed in fluids using vibroacoustic techniques

Journal Article Journal of Applied Physics · March 13, 2007 This work presents an approach to inversely determine material properties for solids immersed in fluids through the use of steady-state dynamic response. The methodology uses measured acoustic pressure amplitudes in the fluid surrounding a structure being ... Full text Cite

Co-evolutionary algorithm for structural damage identification using minimal physical testing

Journal Article International Journal for Numerical Methods in Engineering · January 29, 2007 The problem of damage identification using minimum test data is studied in this work. Data sparsity in damage identification applications commonly results in inverse problems that are mathematically ill-posed (e.g. non-unique solutions). Although solution ... Full text Cite

Implementation of the modified compression field theory in a tangent stiffness-based finite element formulation

Journal Article Steel and Composite Structures · January 1, 2007 A finite element implementation of the modified compression field theory (MCFT) using a tangential formulation is presented in this work. Previous work reported on implementations of MCFT has concentrated mainly on secant formulations. This work describes ... Full text Cite

Self-learning finite elements for inverse estimation of thermal constitutive models

Journal Article International Journal of Heat and Mass Transfer · July 1, 2006 In this work, a new methodology for inverse estimation of thermal constitutive models is introduced. This new methodology combines computational intelligence with finite element analysis for solving inverse heat transfer problems. A neural network (NN) rep ... Full text Cite

Moisture distribution in partially enclosed concrete

Journal Article ACI Materials Journal · July 1, 2004 The most common deterioration problems in reinforced concrete, such as corrosion, alkali-silica reaction, freezing and thawing, sulfate attack, and others, are associated with the presence of elevated moisture contents in the concrete microstructure. An an ... Cite

Analysis and Performance of PCCP Mortar Coating

Journal Article Proceedings of the ASCE International Conference on Pipeline Engineering and Construction: New Pipeline Technologies, Security, and Safety · January 1, 2003 The evaluation of cement mortar coatings on prestressed concrete cylinder pipes (PCCP) may include such techniques as petrographic examination, material testing, and environmental testing of soil and groundwater. Petrographic analysis includes a microscopi ... Full text Cite

The influence of metakaolin and silica fume on the chemistry of alkali-silica reaction products

Journal Article Cement and Concrete Composites · December 1, 2001 This investigation studies the influence of two mineral admixtures, silica fume (SF) and high-reactivity metakaolin (HRM), on the chemistry of alkali-silica reaction (ASR) products. Four different mortar bar mixes containing different combinations of high- ... Full text Cite