scholarly journals Nanocarrier–Cell Surface Adhesive and Hydrodynamic Interactions: Ligand–Receptor Bond Sensitivity Study

2012 ◽  
Vol 3 (3) ◽  
Author(s):  
B. Uma ◽  
R. Radhakrishnan ◽  
D. M. Eckmann ◽  
P. S. Ayyaswamy
Keyword(s):  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Free Energy Density ◽  
Sensitivity Study ◽  
Potential Of Mean Force ◽  
Hydrodynamic Interactions ◽  
Arbitrary Lagrangian Eulerian ◽  
Fluid Medium ◽  
Microscopic Interactions ◽  
Adhesive Interactions

A hybrid approach combining fluctuating hydrodynamics with generalized Langevin dynamics is employed to study the motion of a neutrally buoyant nanocarrier in an incompressible Newtonian stationary fluid medium. Both hydrodynamic interactions and adhesive interactions are included, as are different receptor–ligand bond constants relevant to medical applications. A direct numerical simulation adopting an arbitrary Lagrangian–Eulerian based finite element method is employed for the simulation. The flow around the particle and its motion are fully resolved. The temperatures of the particle associated with the various degrees of freedom satisfy the equipartition theorem. The potential of mean force (or free energy density) along a specified reaction coordinate for the harmonic (spring) interactions between the antibody and antigen is evaluated for two different bond constants. The numerical evaluations show excellent comparison with analytical results. This temporal multiscale modeling of hydrodynamic and microscopic interactions mediating nanocarrier motion and adhesion has important implications for designing nanocarriers for vascular targeted drug delivery.

scholarly journals A Hybrid Approach for the Simulation of the Thermal Motion of a Nearly Neutrally Buoyant Nanoparticle in an Incompressible Newtonian Fluid Medium

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
B. Uma ◽  
R. Radhakrishnan ◽  
D. M. Eckmann ◽  
P. S. Ayyaswamy
Keyword(s):  
Newtonian Fluid ◽  
Brownian Particle ◽  
Equations Of Motion ◽  
Hybrid Approach ◽  
Thermal Motion ◽  
Fluctuating Hydrodynamics ◽  
Arbitrary Lagrangian Eulerian ◽  
Fluid Medium ◽  
Incompressible Newtonian Fluid ◽  
Neutrally Buoyant

A hybrid approach consisting of a Markovian fluctuating hydrodynamics of the fluid and a non-Markovian Langevin dynamics with the Ornstein–Uhlenbeck noise perturbing the translational and rotational equations of motion of a nanoparticle is employed to study the thermal motion of a nearly neutrally buoyant nanoparticle in an incompressible Newtonian fluid medium. A direct numerical simulation adopting an arbitrary Lagrangian–Eulerian based finite element method is employed for the simulation of the hybrid approach. The instantaneous flow around the particle and the particle motion are fully resolved. The numerical results show that (a) the calculated temperature of the nearly neutrally buoyant Brownian particle in a quiescent fluid satisfies the equipartition theorem; (b) the translational and rotational decay of the velocity autocorrelation functions result in algebraic tails, over long time; (c) the translational and rotational mean square displacements of the particle obey Stokes–Einstein and Stokes–Einstein–Debye relations, respectively; and (d) the parallel and perpendicular diffusivities of the particle closer to the wall are consistent with the analytical results, where available. The study has important implications for designing nanocarriers for targeted drug delivery. A major advantage of our novel hybrid approach employed in this paper as compared to either the fluctuating hydrodynamics approach or the generalized Langevin approach by itself is that only the hybrid method has been shown to simultaneously preserve both hydrodynamic correlations and equilibrium statistics in the incompressible limit.

HYBRID CLASSIFICATION STRATEGY OF EMG SIGNALS FOR ROBOTIC HAND CONTROL

2021 ◽  
pp. 2150015
Author(s):  
Fazia sbargoud ◽  
Mohamed Djeha ◽  
Mohamed Guiatni ◽  
Noureddine Ababou
Keyword(s):  
Degrees Of Freedom ◽  
Wavelet Packet ◽  
Hybrid Approach ◽  
Human Motion ◽  
Robotic Hand ◽  
User Intention ◽  
Emg Signal ◽  
Hybrid Classification ◽  
Electromyographic Signal ◽  
Artificial Neural Network Ann

Among the different bio-signals modalities, Electromyographic signal (EMG) has been one of the frequently used signals in the bio-robotics applications field. This is due to the fact that the EMG reflects directly the muscle activity of the user following the human motion intention. Consequently, the decoding of this intention is an essential task for controlling devices such as prosthetic hands and exoskeletons, based on EMG signals. This paper deals with the processing of EMG signals of the forearm muscles, in order to control two degrees of freedom (2 DoFs) robotic hand. The main contribution of this paper is the proposal of a hybrid approach that combines a pattern and a non-pattern recognition-based strategy. The proposed approach aims to take advantage of both strategies and overcome their shortcomings leading to a better analysis of the user movement intention. The EMG recorded signals are processed for feature extraction based on a Wavelet Packet Decomposition (WPD) method and classification using an Artificial Neural Network (ANN). Furthermore, we investigate the effect of the various parameters such as the applied force level, the number of the EMG channels and the window length of the EMG signal. The proposed approach is validated experimentally under realistic conditions. Very interesting results have been obtained for user intention decoding.

Performance Analysis of Nek5000 for Single-Assembly Calculations

2018 ◽  
Author(s):  
Elia Merzari ◽  
Ronald Rahaman ◽  
Misun Min ◽  
Paul Fischer
Keyword(s):  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Reactor Core ◽  
Navier Stokes ◽  
Benchmark Problems ◽  
Application Development ◽  
Pressurized Water ◽  
Eddy Simulation ◽  
Common Framework ◽  
Full Core

The ExasSMR project focuses on the exascale application of single and coupled Monte Carlo (MC) and computational fluid dynamics (CFD) physics. Work is based on the Shift MC depletion, OpenMC temperature-dependent MC, and Nek5000 CFD codes. The application development objective is to optimize these applications for exascale execution of full-core simulations and to modularize and integrate them into a common framework for coupled and individual execution. Given the sheer scale of nuclear systems, the main algorithmic driver on the CFD side is weak scaling. The focus for the first four years of the project is on demonstrating scaling up to a full reactor core for high-fidelity simulations of turbulence. Full-core fluid calculations aimed at better predicting the steady-state performance will be conducted with a hybrid approach in which large eddy simulation is used to simulate a portion of a core and unsteady Reynolds-averaged Navier-Stokes handles the rest. This zonal hybrid approach provides an additional scaling dimension besides the number of assemblies. The present manuscript focuses on performance assessment using assembly-level simulations with Nek5000. We discuss the development of two benchmark problems: a subchannel (single-rod) problem to assess internode performance and a larger full-assembly problem representative of a small modular reactor (SMR). We note that current SMR assemblies are considerably simpler than pressurized water reactor assemblies since they contain no mixing vanes. This feature allows for considerable reduction in the degrees of freedom required to simulate the full core. We discuss profiling and scaling results with Nek5000, describe current bottlenecks and potential limitations of the approach, and suggest optimizations for future investigation.

scholarly journals Fluid-driven origami-inspired artificial muscles

2017 ◽  
Vol 114 (50) ◽  
pp. 13132-13137 ◽  
Author(s):  
Shuguang Li ◽  
Daniel M. Vogt ◽  
Daniela Rus ◽  
Robert J. Wood
Keyword(s):  
Peak Power ◽  
Degrees Of Freedom ◽  
Multiple Scales ◽  
Low Cost ◽  
Artificial Muscles ◽  
Fluid Medium ◽  
Single Degree Of Freedom ◽  
Flexible Skin ◽  
Actuation Systems ◽  
Power Densities

Artificial muscles hold promise for safe and powerful actuation for myriad common machines and robots. However, the design, fabrication, and implementation of artificial muscles are often limited by their material costs, operating principle, scalability, and single-degree-of-freedom contractile actuation motions. Here we propose an architecture for fluid-driven origami-inspired artificial muscles. This concept requires only a compressible skeleton, a flexible skin, and a fluid medium. A mechanical model is developed to explain the interaction of the three components. A fabrication method is introduced to rapidly manufacture low-cost artificial muscles using various materials and at multiple scales. The artificial muscles can be programed to achieve multiaxial motions including contraction, bending, and torsion. These motions can be aggregated into systems with multiple degrees of freedom, which are able to produce controllable motions at different rates. Our artificial muscles can be driven by fluids at negative pressures (relative to ambient). This feature makes actuation safer than most other fluidic artificial muscles that operate with positive pressures. Experiments reveal that these muscles can contract over 90% of their initial lengths, generate stresses of ∼600 kPa, and produce peak power densities over 2 kW/kg—all equal to, or in excess of, natural muscle. This architecture for artificial muscles opens the door to rapid design and low-cost fabrication of actuation systems for numerous applications at multiple scales, ranging from miniature medical devices to wearable robotic exoskeletons to large deployable structures for space exploration.

Numerical Simulation of Glottal Flow in Interaction with Self Oscillating Vocal Folds: Comparison of Finite Element Approximation with a Simplified Model

2012 ◽  
Vol 12 (3) ◽  
pp. 789-806 ◽  
Author(s):  
P. Sváček ◽  
J. Horáček
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Finite Element Approximation ◽  
Vocal Folds ◽  
Multistep Method ◽  
Element Approximation ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Stabilized Finite Element Method

AbstractIn this paper the numerical method for solution of an aeroelastic model describing the interactions of air flow with vocal folds is described. The flow is modelled by the incompressible Navier-Stokes equations spatially discretized with the aid of the stabilized finite element method. The motion of the computational domain is treated with the aid of the Arbitrary Lagrangian Eulerian method. The structure dynamics is replaced by a mechanically equivalent system with the two degrees of freedom governed by a system of ordinary differential equations and discretized in time with the aid of an implicit multistep method and strongly coupled with the flow model. The influence of inlet/outlet boundary conditions is studied and the numerical analysis is performed and compared to the related results from literature.

Towards Development of Uncertainty Library for Nuclear Reactor Core Simulation

2018 ◽  
Author(s):  
Hany S. Abdel-Khalik ◽  
Dongli Huang ◽  
Ondrej Chvala ◽  
G. Ivan Maldonado
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Sensitivity Study ◽  
Reactor Physics ◽  
Rigorous Approach ◽  
Uncertainty Space ◽  
Core Simulation

Uncertainty quantification is an indispensable analysis for nuclear reactor simulation as it provides a rigorous approach by which the credibility of the predictions can be assessed. Focusing on propagation of multi-group cross-sections, the major challenge lies in the enormous size of the uncertainty space. Earlier work has explored the use of the physics-guided coverage mapping (PCM) methodology to assess the quality of the assumptions typically employed to reduce the size of the uncertainty space. A reduced order modeling (ROM) approach has been further developed to identify the active degrees of freedom (DOFs) of the uncertainty space, comprising all the cross-section few-group parameters required in core-wide simulation. In the current work, a sensitivity study, based on the PCM and ROM results, is applied to identify a suitable compressed representation of the uncertainty space to render feasible the quantification and prioritization of the various sources of uncertainties. While the proposed developments are general to any reactor physics computational sequence, the proposed approach is customized to the TRITON-NESTLE computational sequence, simulating the BWR lattice model and the core model, which will serve as a demonstrative tool for the implementation of the algorithms.

Numerical Simulations of Nonlinear Post-Critical Vibrations of an Airfoil After Flutter Instability

2011 ◽  
Author(s):  
Jaromi´r Hora´cˇek ◽  
Miloslav Feistauer ◽  
Petr Sva´cˇek
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Mass Matrix ◽  
Vertical Direction ◽  
Navier Stokes ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
Classical Flutter

The contribution deals with the numerical simulation of the flutter of an airfoil with three degrees of freedom (3-DOF) for rotation around an elastic axis, oscillation in the vertical direction and rotation of a flap. The finite element (FE) solution of two-dimensional (2-D) incompressible Navier-Stokes equations is coupled with a system of nonlinear ordinary differential equations describing the airfoil vibrations with large amplitudes taking into account the nonlinear mass matrix. The time-dependent computational domain and a moving grid are treated by the Arbitrary Lagrangian-Eulerian (ALE) method and a suitable stabilization of the FE discretization is applied. The developed method was successfully tested by the classical flutter computation of the critical flutter velocity using NASTRAN program considering the linear model of vibrations and the double-lattice aerodynamic theory. The method was applied to the numerical simulations of the post flutter regime in time domain showing Limit Cycle Oscillations (LCO) due to nonlinearities of the flow model and vibrations with large amplitudes. Numerical experiments were performed for the airfoil NACA 0012 respecting the effect of the air space between the flap and the main airfoil.

Numerical Investigation of Fluid-Ice-Structure Interaction During Collision by an Arbitrary Lagrangian Eulerian Method

2016 ◽  
Author(s):  
Ming Song ◽  
Ekaterina Kim ◽  
Jørgen Amdahl ◽  
Marilena Greco ◽  
Mhamed Souli
Keyword(s):  
Structural Design ◽  
Sensitivity Study ◽  
Contact Forces ◽  
Theoretical Modelling ◽  
Water Model ◽  
Arbitrary Lagrangian Eulerian ◽  
Ocean Engineering ◽  
Noticeable Effect ◽  
Structure Interaction ◽  
Ale Formulation

When ice floes collide against marine structures, pronounced hydrodynamic loads are induced by the water-ice-structure interaction. With today’s highly competitive structural design market, it is nearly impossible to ignore the advances that have been made in the computer analysis of fluid-structure interaction (FSI) problems. FSI methods can provide accurate representation of hydrodynamic effects. A number of commercial programs have been developed, and their applications in structural design increases rapidly. For instance, Arbitrary Lagrangian-Eulerian (ALE) formulations have been used to solve underwater explosions problems in ocean engineering, and soil-structure interaction problems in civil engineering. Application to fluid-ice-structure interaction problems is more recent and growing. This paper represents a contribution in assessing the capabilities of the ALE formulation for fluid-ice-structure collision problems. The ALE and coupling algorithms have been successfully validated through the comparison against model tests of an ice-structure collision. The work also examines the numerical convergence and the sensitivity of the results to the theoretical modelling used. From the sensitivity study it is concluded that the effect of viscosity and equation of state for the water model within the ALE formulation are insignificant, whereas the choice of the element size has a noticeable effect on the computed contact forces and the motions of the impacted structure.

A Hybrid Approach to Force Balancing of Robotic Mechanisms

2010 ◽  
Author(s):  
J. Huang ◽  
P. R. Ouyang ◽  
L. Cheng ◽  
W. J. Zhang
Keyword(s):  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Kinematic Parameters ◽  
Two Degrees Of Freedom ◽  
Main Motivation ◽  
Simulated Experiment

A hybrid approach to force balancing of robotic mechanisms which have at least two degrees of freedom is proposed. This hybrid approach is to combine adjusting kinematic parameters (AKP) and counterweights (CW) approaches, and it is called AKP+CW in short. The main motivation of the AKP+CW approach is that CW and AKP each has its own advantage and disadvantage, and thus a combined one may strengthen the both. This paper presents the force balancing principles and equations for the AKP+CW approach. Software called ADAMS is employed as a tool for the simulated experiment to verify the effectiveness of the proposed approach. The implication of the work described in this paper to the balancing of mechanisms in general is that many different force balancing methods may be combined based on the hybridization principle proposed in this paper to become a novel one.

scholarly journals A hybrid approach to simulation of electron transfer in complex molecular systems

2013 ◽  
Vol 10 (87) ◽  
pp. 20130415 ◽  
Author(s):  
Tomáš Kubař ◽  
Marcus Elstner
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Degrees Of Freedom ◽  
Hybrid Approach ◽  
Theoretical Description ◽  
Model Systems ◽  
Hole Transfer ◽  
Model Calculations ◽  
Hand Model ◽  
Quantum Mechanical Treatment

Electron transfer (ET) reactions in biomolecular systems represent an important class of processes at the interface of physics, chemistry and biology. The theoretical description of these reactions constitutes a huge challenge because extensive systems require a quantum-mechanical treatment and a broad range of time scales are involved. Thus, only small model systems may be investigated with the modern density functional theory techniques combined with non-adiabatic dynamics algorithms. On the other hand, model calculations based on Marcus's seminal theory describe the ET involving several assumptions that may not always be met. We review a multi-scale method that combines a non-adiabatic propagation scheme and a linear scaling quantum-chemical method with a molecular mechanics force field in such a way that an unbiased description of the dynamics of excess electron is achieved and the number of degrees of freedom is reduced effectively at the same time. ET reactions taking nanoseconds in systems with hundreds of quantum atoms can be simulated, bridging the gap between non-adiabatic ab initio simulations and model approaches such as the Marcus theory. A major recent application is hole transfer in DNA, which represents an archetypal ET reaction in a polarizable medium. Ongoing work focuses on hole transfer in proteins, peptides and organic semi-conductors.

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