Rui Dilao
Instituto Superior Tecnico, Physics, Faculty Member
We present a solvable biped walking model based on an inverted pendulum with two massless articulated legs capable of walking on uneven floors and inclined planes. The stride of the two-legged robot results from the pendular motion of a... more
We present a solvable biped walking model based on an inverted pendulum with two massless articulated legs capable of walking on uneven floors and inclined planes. The stride of the two-legged robot results from the pendular motion of a standing leg and the articulated motion of a trailing leg. Gaiting is possible due to the pendular motion conservation of energy and the alternating role of the legs, the standing and the trailing leg. The motion on uneven surfaces and inclined planes is possible by imposing the same maximal opening angle between the two legs in the transition between strides and the adaptability of the time of each stride. This model is solvable in closed form and is reversible in time, modelling the different types of biped motion. Several optimisation results for the speed of gaiting as a function of the robot parameters have been derived.
Research Interests:
Research Interests:
Research Interests:
Without Abstract
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Algorithms, Physics, Biology, Medicine, Theoretical biology, and 14 moreGene expression, Linear models, Biological Sciences, Computer Simulation, Mathematical Sciences, Negative Feedback, Positive Feedback, Delays, Bistability, Limit Cycles, Protein Binding, Cytoplasm, Protein Biosynthesis, and Gene Expression Regulation
Page 36. EMERGENCE OF A COLLECTIVE STEADY STATE AND SYMMETRY BREAKING IN SYSTEMS OF TWO IDENTICAL CELLS RUI DILAO Nonlinear Dynamics Group, Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisbon, Portugal E-mail: rui@ sd. ist. utl.... more
Page 36. EMERGENCE OF A COLLECTIVE STEADY STATE AND SYMMETRY BREAKING IN SYSTEMS OF TWO IDENTICAL CELLS RUI DILAO Nonlinear Dynamics Group, Instituto Superior Tecnico Av. Rovisco Pais, 1049-001 Lisbon, Portugal E-mail: rui@ sd. ist. utl. ...
Research Interests:
Research Interests:
... 701, Korea Prof R. Dilao, PR Santos, MC Brito Departamento de Fisica, IST, 1096 Lisboa Codex, Portugal Dr. CS Dyer, Dr. AJ Sims Space & Communications Department, DRA, Farnborough, Hampshire, UK Abstract The success ...
Research Interests:
We derive the exact equations of motion of the Keplerian dumbbell (KD) system, which consists of two point masses connected by a rigid massless rod, moving under the gravitational influence of a th...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
A comparison of the behaviour of the topological entropy and the Lyapunov characteristic exponent in the approach of ergodic points is presented.
Research Interests:
We have proposed a mechanism of interaction between two non-linear dissipative oscillators, leading to exact and robust anti-phase and in-phase synchronization. The system we have analyzed is a model for the Huygens’s two pendulum clocks... more
We have proposed a mechanism of interaction between two non-linear dissipative oscillators, leading to exact and robust anti-phase and in-phase synchronization. The system we have analyzed is a model for the Huygens’s two pendulum clocks system, as well as a model for synchronization mediated by an elastic media. Here, we extend these results to arrays, finite or infinite, of conservative pendula coupled by linear elastic forces. We show that, for two interacting pendula, this mechanism leads always to synchronized anti-phase small amplitude oscillations, and it is robust upon variation of the parameters. For three or more interacting pendula, this mechanism leads always to ergodic non-synchronized oscillations. In the continuum limit, the pattern of synchronization is described by a quasi-periodic longitudinal wave.
Research Interests:
Research Interests:
Research Interests: Engineering and Physics
Research Interests:
Research Interests:
A growing population increases the demand for food, but short shelf-lives and microbial hazards reduce supply and increase food waste. Fresh fish is highly perishable and may be consumed raw, such as salmon in sushi. This work aims to... more
A growing population increases the demand for food, but short shelf-lives and microbial hazards reduce supply and increase food waste. Fresh fish is highly perishable and may be consumed raw, such as salmon in sushi. This work aims to identify strategies to improve the shelf-life and safety of fresh salmon, using available methods (i.e., vacuum) and exploring the use of natural preservatives (i.e., seasonings). Vacuum packaging and good hygiene practices (which reduce initial flora) extended shelf-life up to 20 days. Carnobacterium maltaromaticum was dominant in vacuum packaging conditions and showed potential for inhibiting Listeria monocytogenes. For natural preservatives, L. monocytogenes required higher inhibitory concentrations in vitro when compared to the 10 spoilage bacteria isolated from fresh salmon fillets, presenting a minimum inhibitory concentration (MIC) of 0.13% for oregano essential oil (OEO), 10% for lemon juice, 50 mg mL−1 for garlic powder, and >10% for NaCl. ...
Research Interests:
We show that the action potential signals generated by the Hodgkin-Huxley cable model are reaction-diffusion solitons and waves. Action potential spikes travelling in opposite directions of the axon annihilate when colliding with each... more
We show that the action potential signals generated by the Hodgkin-Huxley cable model are reaction-diffusion solitons and waves. Action potential spikes travelling in opposite directions of the axon annihilate when colliding with each other or with the axon boundaries. Through numerical simulations, we characterise the properties of these action potentials, deriving their characteristic curves. We propose several tests to validate or falsify the Hodgkin-Huxley cable model.
Research Interests:
Research Interests:
Research Interests:
We introduce a kinetic model to study the dynamics of ions in aggregates of cells and tissues. Different types of communication channels between adjacent cells and between cells and intracellular space are considered (ion channels, pumps... more
We introduce a kinetic model to study the dynamics of ions in aggregates of cells and tissues. Different types of communication channels between adjacent cells and between cells and intracellular space are considered (ion channels, pumps and gap junctions). We shows that stable transmembrane ionic Nernst potentials are due to the coexistence of both specialised ion pumps and channels. Ion pumps or channels alone do not contribute to an equilibrium transmembrane potential drop. The kinetic parameters of the model straightforwardly calibrate with the Nernst potentials and ion concentrations. The model is based on the ATPase enzymatic mechanism for the ions Na, K, and it can be generalised for other ion pumps. We extend the model to account for electrochemical effects, where transmembrane gating mechanism are introduced. In this framework, axons can be seen as the evolutionary result of the aggregation of cells through gap junctions, which can be identified as the Ranvier nodes. In thi...
Research Interests:
Research Interests:
Space and time scales are not independent in diffusion. In fact, numerical simulations show that different patterns are obtained when space and time steps (Δx and Δt) are varied independently. On the other hand, anisotropy effects due to... more
Space and time scales are not independent in diffusion. In fact, numerical simulations show that different patterns are obtained when space and time steps (Δx and Δt) are varied independently. On the other hand, anisotropy effects due to the symmetries of the discretization lattice prevent the quantitative calibration of models. We introduce a new class of explicit difference methods for numerical integration of diffusion and reaction–diffusion equations, where the dependence on space and time scales occurs naturally. Numerical solutions approach the exact solution of the continuous diffusion equation for finite Δx and Δt, if the parameter γN=DΔt/(Δx)2 assumes a fixed constant value, where N is an odd positive integer parametrizing the algorithm. The error between the solutions of the discrete and the continuous equations goes to zero as (Δx)2(N+2) and the values of γN are dimension independent. With these new integration methods, anisotropy effects resulting from the finite differe...
Research Interests: Mechanical Engineering, Mathematics, Applied Mathematics, Pattern Formation, Numerical Simulation, and 10 moreStandard Deviation, Mathematical Analysis, Discretization, Numerical Integration, Acoustic Diffusion Equation Model, Finite Difference, Numerical Analysis and Computational Mathematics, Bifurcation and Chaos, Continuity Equation, and diffusion equation
Research Interests:
Cell Dynamics: Systems Stem Cell Biology (I Roeder) Emergence of a Collective Steady State and Symmetry Breaking in Plexus of Two and Three Identical Cells (R Dilao) Modeling Infectious Diseases: HIV Epidemiology and the Impact of... more
Cell Dynamics: Systems Stem Cell Biology (I Roeder) Emergence of a Collective Steady State and Symmetry Breaking in Plexus of Two and Three Identical Cells (R Dilao) Modeling Infectious Diseases: HIV Epidemiology and the Impact of Nonsterilizing Vaccines (R Ribeiro et al.) Dynamics of Tuberculosis Under Dots Strategy (P Gomes et al.) Modeling Physiological Disorders: Optimization of Tumor Treatment Based on Mathematical Modeling (J Silveira et al.) Mathematical Prediction of High-Energy Metabolite Gradients in Mammalian Cells (R Mejia & R Lynch) DNA and Proteins: Ideal Protein Forms and Their Application to De Novo Structure Prediction (W Taylor et al.) Multi-Objective Evolutionary Approach to Ab Initio Protein Tertiary Structure Prediction (T de Lima et al.) Population Dynamics: A Stage-Structured Finite Element Model for the Population Dynamics of Two Intertidal Barnacles with Interspecific Competition (A Rio Doce et al.) Advances in a Theory of Impulsive Differential Equations at Impulse-Dependent Times, with Applications to the Mathematical Bioeconomics (F Cordova-Lepe) and other papers.
Research Interests:
Research Interests:
ABSTRACT We have proposed a mechanism of interaction between two non-linear dissipative oscillators, leading to exact and robust anti-phase and in-phase synchronization. The system we have analyzed is a model for the Huygens’s two... more
ABSTRACT We have proposed a mechanism of interaction between two non-linear dissipative oscillators, leading to exact and robust anti-phase and in-phase synchronization. The system we have analyzed is a model for the Huygens’s two pendulum clocks system, as well as a model for synchronization mediated by an elastic media. Here, we extend these results to arrays, finite or infinite, of conservative pendula coupled by linear elastic forces. We show that, for two interacting pendula, this mechanism leads always to synchronized anti-phase small amplitude oscillations, and it is robust upon variation of the parameters. For three or more interacting pendula, this mechanism leads always to ergodic non-synchronized oscillations. In the continuum limit, the pattern of synchronization is described by a quasi-periodic longitudinal wave.
Research Interests:
Research Interests:
Based on the law of mass action (and its microscopic foundation) and mass conservation, we present here a method to derive consistent dynamic models for the time evolution of systems with an arbitrary number of species. Equations are... more
Based on the law of mass action (and its microscopic foundation) and mass conservation, we present here a method to derive consistent dynamic models for the time evolution of systems with an arbitrary number of species. Equations are derived through a mechanistic description, ensuring that all parameters have ecological meaning. After discussing the biological mechanisms associated to the logistic and Lotka-Volterra equations, we show how to derive general models for trophic chains, including the effects of internal states at fast time scales. We show that conformity with the mass action law leads to different functional forms for the Lotka-Volterra and trophic chain models. We use mass conservation to recover the concept of carrying capacity for an arbitrary food chain.
Research Interests:
Research Interests:
Research Interests:
In 26 February 1665, Christiaan Huygens, in a letter to his father [1], reported the observation of the synchronization of two pendulum clocks closely hanged on the wall of his workshop. After synchronization, the clocks swung exactly in... more
In 26 February 1665, Christiaan Huygens, in a letter to his father [1], reported the observation of the synchronization of two pendulum clocks closely hanged on the wall of his workshop. After synchronization, the clocks swung exactly in the same frequency and 180 ◦ out of phase. ...
Research Interests:
Research Interests:
Antiphase and in-phase synchronization of nonlinear oscillators: The Huygens's clocks system. [Chaos: An Interdisciplinary Journal of Nonlinear Science 19, 023118 (2009)]. Rui Dilão. Abstract. We introduce an interaction mechanism ...