736 research outputs found
Modeling human intuitions about liquid flow with particle-based simulation
Humans can easily describe, imagine, and, crucially, predict a wide variety
of behaviors of liquids--splashing, squirting, gushing, sloshing, soaking,
dripping, draining, trickling, pooling, and pouring--despite tremendous
variability in their material and dynamical properties. Here we propose and
test a computational model of how people perceive and predict these liquid
dynamics, based on coarse approximate simulations of fluids as collections of
interacting particles. Our model is analogous to a "game engine in the head",
drawing on techniques for interactive simulations (as in video games) that
optimize for efficiency and natural appearance rather than physical accuracy.
In two behavioral experiments, we found that the model accurately captured
people's predictions about how liquids flow among complex solid obstacles, and
was significantly better than two alternatives based on simple heuristics and
deep neural networks. Our model was also able to explain how people's
predictions varied as a function of the liquids' properties (e.g., viscosity
and stickiness). Together, the model and empirical results extend the recent
proposal that human physical scene understanding for the dynamics of rigid,
solid objects can be supported by approximate probabilistic simulation, to the
more complex and unexplored domain of fluid dynamics.Comment: Under review at PLOS Computational Biolog
A thermodynamics-informed active learning approach to perception and reasoning about fluids
Learning and reasoning about physical phenomena is still a challenge in robotics development, and computational sciences play a capital role in the search for accurate methods able to provide explanations for past events and rigorous forecasts of future situations. We propose a thermodynamics-informed active learning strategy for fluid perception and reasoning from observations. As a model problem, we take the sloshing phenomena of different fluids contained in a glass. Starting from full-field and high-resolution synthetic data for a particular fluid, we develop a method for the tracking (perception) and simulation (reasoning) of any previously unseen liquid whose free surface is observed with a commodity camera. This approach demonstrates the importance of physics and knowledge not only in data-driven (gray-box) modeling but also in real-physics adaptation in low-data regimes and partial observations of the dynamics. The presented method is extensible to other domains such as the development of cognitive digital twins able to learn from observation of phenomena for which they have not been trained explicitly
A thermodynamics-informed active learning approach to perception and reasoning about fluids
Learning and reasoning about physical phenomena is still a challenge in robotics development, and computational sciences
play a capital role in the search for accurate methods able to provide explanations for past events and rigorous forecasts
of future situations. We propose a thermodynamics-informed active learning strategy for fluid perception and reasoning
from observations. As a model problem, we take the sloshing phenomena of different fluids contained in a glass. Starting
from full-field and high-resolution synthetic data for a particular fluid, we develop a method for the tracking (perception)
and simulation (reasoning) of any previously unseen liquid whose free surface is observed with a commodity camera. This
approach demonstrates the importance of physics and knowledge not only in data-driven (gray-box) modeling but also in
real-physics adaptation in low-data regimes and partial observations of the dynamics. The presented method is extensible to
other domains such as the development of cognitive digital twins able to learn from observation of phenomena for which they
have not been trained explicitly
From task structures to world models: What do LLMs know?
In what sense does a large language model have knowledge? The answer to this
question extends beyond the capabilities of a particular AI system, and
challenges our assumptions about the nature of knowledge and intelligence. We
answer by granting LLMs "instrumental knowledge"; knowledge defined by a
certain set of abilities. We then ask how such knowledge is related to the more
ordinary, "worldly" knowledge exhibited by human agents, and explore this in
terms of the degree to which instrumental knowledge can be said to incorporate
the structured world models of cognitive science. We discuss ways LLMs could
recover degrees of worldly knowledge, and suggest such recovery will be
governed by an implicit, resource-rational tradeoff between world models and
task demands
Using Novel Approaches for Navigating Complex Energy Landscapes: Ion Channel Conductance using Hyperdynamics and Human-Guided Global Optimization of Lennard-Jones Clusters
Molecular dynamics (MD) is a widely used tool to study molecular systems on atomic level. However, the timescale of a traditional MD simulation is typically limited to nanoseconds. Thus many interesting processes that occur on microseconds or larger timescale can\u27t be studied. Hyperdynamics provides a way to extend the timescale of MD simulation. In hyperdynamics, MD is performed on a biased potential then corrected to get true dynamics provided certain conditions are met. Here, we tried to study potassium channel conductance using the hyperdynamics method with a bias potential constructed based on the potential of mean force of ion translocation through the selective filter of a potassium ion channel. However, when MD was performed on this biased potential, no ion translocation events were observed. Although some new insights were gained into the rate-limiting steps for ion mobility in this system from these negative results, no further studies are planned with this project.
The second project is based on the assumption that hybrid human{computational algorithm is more efficient than purely computational algorithm itself. Such ideas have already been studied by many \crowd-sourcing games, such as Foldit [1] for the protein structure prediction problem, and QuantumMoves [2] for quantum physics. Here, the same idea is applied to cluster structure optimization. A virtual reality android cellphone app was developed to study global optimization of Lennard-Jones clusters with both computational algorithm and hybrid human{computational algorithm. Using linear mixed model analysis, we found statistically significant differences between the expected runtime of both methods, at least for cluster of certain sizes. Further analysis of the data showing human intelligence weakened the strong dependence of the efficiency of the computational method on cluster sizes. We hypothesis that this is due to that humans are able to make large moves that allows the algorithm to cover a large region in the potential energy surface faster. Further studies with more cluster sizes are needed to draw a more complete conclusion. Human intelligence can potentially be integrated into more advanced optimization technique and applied to more complicated optimization problems in the future. Patterns analysis of human behaviors during the optimization process can be conducted to gain insights of mechanisms and strategies of optimization process
Physics perception in sloshing scenes with guaranteed thermodynamic consistency
Physics perception very often faces the problem that only limited data or
partial measurements on the scene are available. In this work, we propose a
strategy to learn the full state of sloshing liquids from measurements of the
free surface. Our approach is based on recurrent neural networks (RNN) that
project the limited information available to a reduced-order manifold so as to
not only reconstruct the unknown information, but also to be capable of
performing fluid reasoning about future scenarios in real time. To obtain
physically consistent predictions, we train deep neural networks on the
reduced-order manifold that, through the employ of inductive biases, ensure the
fulfillment of the principles of thermodynamics. RNNs learn from history the
required hidden information to correlate the limited information with the
latent space where the simulation occurs. Finally, a decoder returns data back
to the high-dimensional manifold, so as to provide the user with insightful
information in the form of augmented reality. This algorithm is connected to a
computer vision system to test the performance of the proposed methodology with
real information, resulting in a system capable of understanding and predicting
future states of the observed fluid in real-time.Comment: 20 pages, 11 figure
Learning and Simulation Algorithms for Constraint Physical Systems
This thesis explores two computational approaches to learn and simulate complex physical systems exhibiting constraint characteristics. The target applications encompass both solids and fluids. On the solid side, we proposed a new family of data-driven simulators to predict the behaviors of an unknown physical system by learning its underpinning constraints. We devised a neural projection operator facilitated by an embedded recursive neural network to interactively enforce the learned underpinning constraints and to predict its various physical behaviors. Our method can automatically uncover a broad range of constraints from observation point data, such as length, angle, bending, collision, boundary effects, and their combinations, in the context of a diverse set of physical systems including rigid bodies, ropes, articulated bodies, and multi-object collisions. On the fluid side, we proposed a gauge numerical simulator to model fluid phenomena using Clebsch wave functions. Our method combines the expressive power of Clebsch wave functions to represent coherent vortical structures and the generality of gauge methods to accommodate a broad array of fluid phenomena. We devised a transformed wave function as the system’s gauge variable to improve a fluid simulator’s vorticity generation and preservation ability. We showcase our method by simulating various types of incompressible flow phenomena, including complex vortex filament dynamics, fluids with different obstacles, and surface-tension flow
Minor Whey Protein Purification Using Ion-Exchange Column Chromatography
This thesis is concerned with application of mechanistic models for recovery and purification of two minor milk proteins to develop an efficient and robust process. A fundamental and quantitative understanding of the underlying mechanisms assists to evaluate chances and challenges in non-linear chromatography.
The first chapter considers adsorption isotherm data of two minor whey proteins on cation exchanger under various conditions and used as the basis to develop a predictive approach for correlating adsorption behavior using a mechanistic isotherm model. The SMA isotherm model explicitly considers the contributions of protein-adsorbent and protein-protein interactions in the simulation of salt gradients in ion exchange chromatography.Sensitivity and robustness analysis by factorial design of experiments within this framework showed to be highly consistent and even allowed for upscale predictions with an excellent quality.
In the next part of the thesis, the nonlinear gradient elution was to be optimized by three process factors the length of gradient, final salt concentration at the end of gradient and flow velocity. Predictions based on response surface modeling (RSM) approach were applied to reveal significant process factors. The optimal operating point was then determined by calibrated mechanistic model within and outside the design space. The operating conditions containing optimal information were experimentally verified which confirmed simulations accuracy.
The third chapter considers the effects of scale-up and operating conditions on dynamic adsorption of proteins. For two columns having similar bed height, flow distribution properties was observed under non-binding conditions. Elution profiles were employed to determine dominant mass transport mechanisms. Breakthrough profiles were compared at different flow rates and protein loading concentrations.The efficiency of the columns in terms of HETP and dynamic binding capacity were calculated and compared for two columns.
The outcomes resulting from the application of mechanistic models to the purification of lactoperoxidase and lactoferrin in this thesis exploit the platform for the next step towards the recovery of high-value proteins at industrial scales
Analytical continuum mechanics \`a la Hamilton-Piola: least action principle for second gradient continua and capillary fluids
In this paper a stationary action principle is proven to hold for capillary
fluids, i.e. fluids for which the deformation energy has the form suggested,
starting from molecular arguments, for instance by Cahn and Hilliard. Remark
that these fluids are sometimes also called Korteweg-de Vries or Cahn-Allen. In
general continua whose deformation energy depend on the second gradient of
placement are called second gradient (or Piola-Toupin or Mindlin or
Green-Rivlin or Germain or second gradient) continua. In the present paper, a
material description for second gradient continua is formulated. A Lagrangian
action is introduced in both material and spatial description and the
corresponding Euler-Lagrange bulk and boundary conditions are found. These
conditions are formulated in terms of an objective deformation energy volume
density in two cases: when this energy is assumed to depend on either C and
grad C or on C^-1 and grad C^-1 ; where C is the Cauchy-Green deformation
tensor. When particularized to energies which characterize fluid materials, the
capillary fluid evolution conditions (see e.g. Casal or Seppecher for an
alternative deduction based on thermodynamic arguments) are recovered. A
version of Bernoulli law valid for capillary fluids is found and, in the
Appendix B, useful kinematic formulas for the present variational formulation
are proposed. Historical comments about Gabrio Piola's contribution to
continuum analytical mechanics are also presented. In this context the reader
is also referred to Capecchi and Ruta.Comment: 52 page
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