As cities expand, human mobility has become a central focus of urban planning and policy making t... more As cities expand, human mobility has become a central focus of urban planning and policy making to make cities more inclusive and sustainable. Initiatives such as the “15-minutes city” have been put in place to shift the attention from monocentric city configurations to polycentric structures, increasing the availability and diversity of local urban amenities. Ultimately they expect to increase local walkability and increase mobility within residential areas. While we know how urban amenities influence human mobility at the city level, little is known about spatial variations in this relationship. Here, we use mobile phone, census, and volunteered geographical data to measure geographic variations in the relationship between origin-destination flows and local urban accessibility in Barcelona. Using a Negative Binomial Geographically Weighted Regression model, we show that, globally, people tend to visit neighborhoods with better access to education and retail. Locally, these and oth...
The visual communication of climate information is one of the cornerstones of climate services. I... more The visual communication of climate information is one of the cornerstones of climate services. It often requires the translation of multidimensional data to visual channels by combining colors, distances, angles, and glyph sizes. However, visualizations including too many layers of complexity can hinder decision-making processes by limiting the cognitive capacity of users, therefore affecting their attention, recognition, and working memory. Methodologies grounded on the fields of user-centered design, user interaction and cognitive psychology, which are based on the needs of the users, have a lot to contribute to the climate data visualization field. Here, we apply these methodologies to the redesign of an existing climate service tool tailored to the wind energy sector. We quantify the effect of the redesign on the users’ experience performing typical daily tasks, using both quantitative and qualitative indicators that include response time, success ratios, eye-tracking measures,...
ABSTRACT I will show how to perform a time reversal of the dynamics of cold bosonic atoms in an o... more ABSTRACT I will show how to perform a time reversal of the dynamics of cold bosonic atoms in an optical lattice. The time reversal creates a Loschmidt echo and is obtained by applying a linear phase imprint on the lattice and a change in magnetic field to tune the boson-boson scattering length through a Feshbach resonance. I will discuss how to use the echo as a sensor to measure intensities of external potentials (e.g. gravity, magnetic fields, etc.), and also interesting quantities such as the fidelity of the quantum simulation of the Bose-Hubbard Hamiltonian, and the critical point and exponents of the superfluid-insulator quantum phase transition in this model.
We examine an exactly solvable model of decoherence -- a spin-system interacting with a collectio... more We examine an exactly solvable model of decoherence -- a spin-system interacting with a collection of environment spins. We show that in this simple model (introduced some time ago to illustrate environment--induced superselection) generic assumptions about the coupling strengths lead to a universal (Gaussian) suppression of coherence between pointer states. We explore the regime of validity of this result and discuss its relation to spectral features of the environment. We also consider its relevance to the experiments on the so-called Loschmidt echo (which measures, in effect, the fidelity between the initial and time-reversed or "echo" signal). In particular, we show that for partial reversals (e.g., when of only a part of the total Hamiltonian changes sign) fidelity will exhibit a Gaussian dependence on the time of reversal. In such cases echo may become independent of the details of the reversal procedure or the specifics of the coupling to the environment. This puzzling behavior was observed in several NMR experiments. Natural candidates for such two environments (one of which is easily reversed, while the other is ``irreversible'') are suggested for the experiment involving ferrocene.
ABSTRACT I show how to perform a Loschmidt echo (time reversal) in the Bose-Hubbard model impleme... more ABSTRACT I show how to perform a Loschmidt echo (time reversal) in the Bose-Hubbard model implemented with cold bosonic atoms in an optical lattice. The echo is obtained by applying a linear phase imprint on the lattice and a change in magnetic field to tune the boson-boson scattering length through a Feshbach resonance. I discuss how the echo can measure the fidelity of the quantum simulation, and also the intensity of an external potential (e.g. gravity), or the critical point of the superfluid-insulator quantum phase transition.
The recycling of end-of-life concrete into new cement is one of the most interesting options for ... more The recycling of end-of-life concrete into new cement is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The production of the cement used in concrete, for example, is responsible for at least 5% of worldwide CO2 emissions. After segregation from other demolition waste and some pre-processing, re-using the recovered concrete has the potential to cut carbon dioxide emissions in the production of new cement by a factor of two. At the heart of the cement production process lies the kiln, a tilted rotary oven where raw materials are heated to reaction temperatures to form small cement pellets called clinker, which is then ground to make cement powder. In addition to reducing its raw material consumption, improving the efficiency of cement kiln is a main concern of the industry, as the kiln is the main consumer of energy in the production process. Therefore, in the last decade there has been gro...
2012 SC Companion: High Performance Computing, Networking Storage and Analysis, 2012
ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report,... more ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report, accompanying the video Two fluids level set: High performance simulation and post processing" presents the implementation of a Level Set method for two fluid flows in the parallel finite element code Alya that can scale up to thousands of processors. To give an idea of the versatility of the implementation examples extending from the flushing of a toilet to the simulation of free surface flows around ship hulls are presented. The spatial discretization is based on unstructured linear finite elements, tetrahedras and prisms that allow a great degree of flexibility for complex geometries as will be shown in the examples. The time discretization uses a standard trapezoidal rule. The position of the moving interface is captured with the Level Set technique that is better suited for complex flows than interface tracking schemes. The jump in the fluid properties is smoothed in a region close to the interface. For ship hydrodynamics simulations the model has been coupled with the SST k-ω turbulence model.
A neutral impurity atom immersed in a dilute Bose-Einstein condensate (BEC) can have a bound grou... more A neutral impurity atom immersed in a dilute Bose-Einstein condensate (BEC) can have a bound ground state in which the impurity is self-localized. In this polaronlike state, the impurity distorts the density of the surrounding BEC, thereby creating the self-trapping potential minimum. We describe the self-localization in a strong-coupling approach.
Physical review. E, Statistical, nonlinear, and soft matter physics, 2002
Classical chaotic dynamics is characterized by exponential sensitivity to initial conditions. Qua... more Classical chaotic dynamics is characterized by exponential sensitivity to initial conditions. Quantum mechanics, however, does not show this feature. We consider instead the sensitivity of quantum evolution to perturbations in the Hamiltonian. This is observed as an attenuation of the Loschmidt echo M(t), i.e., the amount of the original state (wave packet of width sigma) which is recovered after a time reversed evolution, in the presence of a classically weak perturbation. By considering a Lorentz gas of size L, which for large L is a model for an unbounded classically chaotic system, we find numerical evidence that, if the perturbation is within a certain range, M(t) decays exponentially with a rate 1/tau(phi) determined by the Lyapunov exponent lambda of the corresponding classical dynamics. This exponential decay extends much beyond the Eherenfest time t(E) and saturates at a time t(s) approximately equal to lambda(-1)ln[N], where N approximately (L/sigma)(2) is the effective di...
As cities expand, human mobility has become a central focus of urban planning and policy making t... more As cities expand, human mobility has become a central focus of urban planning and policy making to make cities more inclusive and sustainable. Initiatives such as the “15-minutes city” have been put in place to shift the attention from monocentric city configurations to polycentric structures, increasing the availability and diversity of local urban amenities. Ultimately they expect to increase local walkability and increase mobility within residential areas. While we know how urban amenities influence human mobility at the city level, little is known about spatial variations in this relationship. Here, we use mobile phone, census, and volunteered geographical data to measure geographic variations in the relationship between origin-destination flows and local urban accessibility in Barcelona. Using a Negative Binomial Geographically Weighted Regression model, we show that, globally, people tend to visit neighborhoods with better access to education and retail. Locally, these and oth...
The visual communication of climate information is one of the cornerstones of climate services. I... more The visual communication of climate information is one of the cornerstones of climate services. It often requires the translation of multidimensional data to visual channels by combining colors, distances, angles, and glyph sizes. However, visualizations including too many layers of complexity can hinder decision-making processes by limiting the cognitive capacity of users, therefore affecting their attention, recognition, and working memory. Methodologies grounded on the fields of user-centered design, user interaction and cognitive psychology, which are based on the needs of the users, have a lot to contribute to the climate data visualization field. Here, we apply these methodologies to the redesign of an existing climate service tool tailored to the wind energy sector. We quantify the effect of the redesign on the users’ experience performing typical daily tasks, using both quantitative and qualitative indicators that include response time, success ratios, eye-tracking measures,...
ABSTRACT I will show how to perform a time reversal of the dynamics of cold bosonic atoms in an o... more ABSTRACT I will show how to perform a time reversal of the dynamics of cold bosonic atoms in an optical lattice. The time reversal creates a Loschmidt echo and is obtained by applying a linear phase imprint on the lattice and a change in magnetic field to tune the boson-boson scattering length through a Feshbach resonance. I will discuss how to use the echo as a sensor to measure intensities of external potentials (e.g. gravity, magnetic fields, etc.), and also interesting quantities such as the fidelity of the quantum simulation of the Bose-Hubbard Hamiltonian, and the critical point and exponents of the superfluid-insulator quantum phase transition in this model.
We examine an exactly solvable model of decoherence -- a spin-system interacting with a collectio... more We examine an exactly solvable model of decoherence -- a spin-system interacting with a collection of environment spins. We show that in this simple model (introduced some time ago to illustrate environment--induced superselection) generic assumptions about the coupling strengths lead to a universal (Gaussian) suppression of coherence between pointer states. We explore the regime of validity of this result and discuss its relation to spectral features of the environment. We also consider its relevance to the experiments on the so-called Loschmidt echo (which measures, in effect, the fidelity between the initial and time-reversed or "echo" signal). In particular, we show that for partial reversals (e.g., when of only a part of the total Hamiltonian changes sign) fidelity will exhibit a Gaussian dependence on the time of reversal. In such cases echo may become independent of the details of the reversal procedure or the specifics of the coupling to the environment. This puzzling behavior was observed in several NMR experiments. Natural candidates for such two environments (one of which is easily reversed, while the other is ``irreversible'') are suggested for the experiment involving ferrocene.
ABSTRACT I show how to perform a Loschmidt echo (time reversal) in the Bose-Hubbard model impleme... more ABSTRACT I show how to perform a Loschmidt echo (time reversal) in the Bose-Hubbard model implemented with cold bosonic atoms in an optical lattice. The echo is obtained by applying a linear phase imprint on the lattice and a change in magnetic field to tune the boson-boson scattering length through a Feshbach resonance. I discuss how the echo can measure the fidelity of the quantum simulation, and also the intensity of an external potential (e.g. gravity), or the critical point of the superfluid-insulator quantum phase transition.
The recycling of end-of-life concrete into new cement is one of the most interesting options for ... more The recycling of end-of-life concrete into new cement is one of the most interesting options for reducing worldwide natural resources use and emissions associated with the building materials sector. The production of the cement used in concrete, for example, is responsible for at least 5% of worldwide CO2 emissions. After segregation from other demolition waste and some pre-processing, re-using the recovered concrete has the potential to cut carbon dioxide emissions in the production of new cement by a factor of two. At the heart of the cement production process lies the kiln, a tilted rotary oven where raw materials are heated to reaction temperatures to form small cement pellets called clinker, which is then ground to make cement powder. In addition to reducing its raw material consumption, improving the efficiency of cement kiln is a main concern of the industry, as the kiln is the main consumer of energy in the production process. Therefore, in the last decade there has been gro...
2012 SC Companion: High Performance Computing, Networking Storage and Analysis, 2012
ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report,... more ABSTRACT Flows with moving interfaces appear in a wide range of real world problems. This report, accompanying the video Two fluids level set: High performance simulation and post processing" presents the implementation of a Level Set method for two fluid flows in the parallel finite element code Alya that can scale up to thousands of processors. To give an idea of the versatility of the implementation examples extending from the flushing of a toilet to the simulation of free surface flows around ship hulls are presented. The spatial discretization is based on unstructured linear finite elements, tetrahedras and prisms that allow a great degree of flexibility for complex geometries as will be shown in the examples. The time discretization uses a standard trapezoidal rule. The position of the moving interface is captured with the Level Set technique that is better suited for complex flows than interface tracking schemes. The jump in the fluid properties is smoothed in a region close to the interface. For ship hydrodynamics simulations the model has been coupled with the SST k-ω turbulence model.
A neutral impurity atom immersed in a dilute Bose-Einstein condensate (BEC) can have a bound grou... more A neutral impurity atom immersed in a dilute Bose-Einstein condensate (BEC) can have a bound ground state in which the impurity is self-localized. In this polaronlike state, the impurity distorts the density of the surrounding BEC, thereby creating the self-trapping potential minimum. We describe the self-localization in a strong-coupling approach.
Physical review. E, Statistical, nonlinear, and soft matter physics, 2002
Classical chaotic dynamics is characterized by exponential sensitivity to initial conditions. Qua... more Classical chaotic dynamics is characterized by exponential sensitivity to initial conditions. Quantum mechanics, however, does not show this feature. We consider instead the sensitivity of quantum evolution to perturbations in the Hamiltonian. This is observed as an attenuation of the Loschmidt echo M(t), i.e., the amount of the original state (wave packet of width sigma) which is recovered after a time reversed evolution, in the presence of a classically weak perturbation. By considering a Lorentz gas of size L, which for large L is a model for an unbounded classically chaotic system, we find numerical evidence that, if the perturbation is within a certain range, M(t) decays exponentially with a rate 1/tau(phi) determined by the Lyapunov exponent lambda of the corresponding classical dynamics. This exponential decay extends much beyond the Eherenfest time t(E) and saturates at a time t(s) approximately equal to lambda(-1)ln[N], where N approximately (L/sigma)(2) is the effective di...
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Papers by Fernando Cucchietti