Papers by Diego Pedro Gonzalez
2019 24th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA)
On-orbit satellite servicing is a technology that is expected to transform the space sector in th... more On-orbit satellite servicing is a technology that is expected to transform the space sector in the coming years. Space robotics is a promising approach to refuel, repair, update, and transport satellites on orbit. However, safe and reliable docking with the client satellite, needed as part of most servicing operations, is still considered a challenge. This paper presents an autonomous robot-based approach for this purpose. An impedance control strategy is added to the controller of a conventional robotic manipulator to allow compliant and safe manipulation of a spacecraft docking mechanism. This setup is expected to facilitate autonomous docking and manipulation operations with cooperative and non-cooperative on-orbit serviced satellites. Platform-art © , a dynamic test bench for hardware-in-the-loop validation of space GNC technologies is used to test the proposed approach.
Physical Review B
We study the quantum metric tensor and its scalar curvature for a particular version of the Lipki... more We study the quantum metric tensor and its scalar curvature for a particular version of the Lipkin-Meshkov-Glick model. We build the classical Hamiltonian using Bloch coherent states and find its stationary points. They exhibit the presence of a ground state quantum phase transition, where a bifurcation occurs, showing a change of stability associated with an excited state quantum phase transition. Symmetrically, for a sign change in one Hamiltonian parameter, the same phenomenon is observed in the highest energy state. Employing the Holstein-Primakoff approximation, we derive analytic expressions for the quantum metric tensor and compute the scalar and Berry curvatures. We contrast the analytic results with their finite-size counterparts obtained through exact numerical diagonalization and find an excellent agreement between them for large sizes of the system in a wide region of the parameter space, except in points near the phase transition where the Holstein-Primakoff approximation ceases to be valid.
Journal of Physics A: Mathematical and Theoretical
The geometry of the parameter space is encoded by the quantum geometric tensor, which captures fu... more The geometry of the parameter space is encoded by the quantum geometric tensor, which captures fundamental information about quantum states and contains both the quantum metric tensor and the curvature of the Berry connection. We present a formulation of the Berry connection and the quantum geometric tensor in the framework of the phase space or Wigner function formalism. This formulation is obtained through the direct application of the Weyl correspondence to the geometric structure under consideration. In particular, we show that the quantum metric tensor can be computed using only the Wigner functions, which opens an alternative way to experimentally measure the components of this tensor. We also address the non-Abelian generalization and obtain the phase space formulation of the Wilczek–Zee connection and the non-Abelian quantum geometric tensor. In this case, the non-Abelian quantum metric tensor involves only the non-diagonal Wigner functions. Then, we verify our approach with...
This paper shows a simple and effective approach to the design and implementation of Industrial I... more This paper shows a simple and effective approach to the design and implementation of Industrial Information Systems (IIS) oriented to control the characteristics of each individual product manufactured in a production line and also their manufacturing conditions. The particular products considered in this work are large steel strips that are coiled just after their manufacturing. However, the approach is directly applicable to coiled strips in other industries, like paper, textile, aluminum, etc. These IIS provide very detailed information of each manufactured product, which complement the general information managed by the ERP system of the production line. In spite of the high importance of this type of IIS to guarantee and improve the quality of the products manufactured in many industries, there are very few works about them in the technical literature. For this reason, this paper represents an important contribution to the development of this type of IIS, providing guidelines f...
Physical Review E, 2021
We study the classical analog of the quantum metric tensor and its scalar curvature for two well-... more We study the classical analog of the quantum metric tensor and its scalar curvature for two well-known quantum physics models. First, we analyze the geometry of the parameter space for the Dicke model with the aid of the classical and quantum metrics and find that, in the thermodynamic limit, they have the same divergent behavior near the quantum phase transition, as opposed to their corresponding scalar curvatures which are not divergent there. On the contrary, under resonance conditions, both scalar curvatures exhibit a divergence at the critical point. Second, we present the classical and quantum metrics for the Lipkin-Meshkov-Glick model in the thermodynamic limit and find a perfect agreement between them. We also show that the scalar curvature is only defined on one of the system's phases and that it approaches a negative constant value. Finally, we carry out a numerical analysis for the system's finite sizes, which clearly shows the precursors of the quantum phase transition in the metric and its scalar curvature and allows their characterization as functions of the parameters and of the system's size.
Physical Review D, 2021
We report new topological invariants in four dimensions that are generalizations of the Nieh-Yan ... more We report new topological invariants in four dimensions that are generalizations of the Nieh-Yan topological invariant. The new topological invariants are obtained through a systematic method along the lines of the one used to get the Nieh-Yan form, but involving an SO(4, 1) [SO(5)] connection constructed out from an SO(3, 1) [SO(4)] connection and three SO(3, 1) [SO(4)] tensor 1-forms. We give explicit expressions of the new 4-forms that give rise to the new topological invariants for particular choices of these 1-forms and show that the Nieh-Yan form arises as a particular case.
Symmetry, 2021
We report off-shell Noether currents obtained from off-shell Noether potentials for first-order g... more We report off-shell Noether currents obtained from off-shell Noether potentials for first-order general relativity described by n-dimensional Palatini and Holst Lagrangians including the cosmological constant. These off-shell currents and potentials are achieved by using the corresponding Lagrangian and the off-shell Noether identities satisfied by diffeomorphisms generated by arbitrary vector fields, local SO(n) or SO(n−1,1) transformations, ‘improved diffeomorphisms’, and the ‘generalization of local translations’ of the orthonormal frame and the connection. A remarkable aspect of our approach is that we do not use Noether’s theorem in its direct form. By construction, the currents are off-shell conserved and lead naturally to the definition of off-shell Noether charges. We also study what we call the ‘half off-shell’ case for both Palatini and Holst Lagrangians. In particular, we find that the resulting diffeomorphism and local SO(3,1) or SO(4) off-shell Noether currents and pote...
Computers & Graphics, 2018
We present a novel approach for 3D shape synthesis from a collection of existing models. The main... more We present a novel approach for 3D shape synthesis from a collection of existing models. The main idea of our approach is to synthesize shapes by recombining fine-grained parts extracted from the existing models based purely on the objects' geometry. Thus, unlike most previous works, a key advantage of our method is that it does not require a semantic segmentation, nor part correspondences between the shapes of the input set. Our method uses a template shape to guide the synthesis. After extracting a set of fine-grained segments from the input dataset, we compute the similarity among the segments in the collection and segments of the template using shape descriptors. Next, we use the similarity estimates to select, from the set of fine-grained segments, compatible replacements for each part of the template. By sampling different segments for each part of the template, and by using different templates, our method can synthesize many distinct shapes that have a variety of local fine details. Additionally, we maintain the plausibility of the objects by preserving the general structure of the template. We show with several experiments performed on different datasets that our algorithm can be used for synthesizing a wide variety of man-made objects.
Defect and Diffusion Forum, 2018
Since the development of the Ti54M titanium alloy in 2003, its application within the aerospace s... more Since the development of the Ti54M titanium alloy in 2003, its application within the aerospace sector has gradually increased due to the combination of properties such as improved forgeability and machinability, low flow stress at elevated temperatures, and superplastic characteristics. However, for the successful exploitation of Ti54M a comprehensive understanding of its mechanical characteristics, microstructure stability, and superplastic behaviour is required. The superplastic forming of titanium alloys is characterised by high deformation at slow strain rates and high temperatures which influence the material microstructure, and in turn, determine the forming parameters. These mechanisms make the prediction of the material behaviour very challenging, limiting its application within the aerospace industry. Even though Ti54M has been commercially available for over 10 years, further studies of its mechanical and superplastic properties are still required with the aim of assessin...
Proceedings of the National Academy of Sciences of the United States of America, Jul 2, 2018
Competition in animals involves a wide variety of aggressive behaviors. One of the most sophistic... more Competition in animals involves a wide variety of aggressive behaviors. One of the most sophisticated strategies for a focal actor is to provoke a competitor into uncontrolled aggression toward other competitors. Like animals, bacteria rely on a broad spectrum of molecular weapons, some of which provoke potential rivals by triggering retaliation. While bacterial provocation is well documented, its potential adaptive value has received little attention. Here, we examine the costs and benefits of provocation using mathematical modeling and experiments with strains encoding colicin toxins. We show that provocation is typically costly in one-to-one encounters because a provoking strain receives a strong reciprocal attack compared with nonprovoking strains. By contrast, provocation can be strongly beneficial in communities including more than two toxin-producing strains, especially when the provoker is shielded from, or resistant to, its opponents' toxins. In these scenarios, we demo...
Classical and Quantum Gravity, 2017
We report a new internal gauge symmetry of the n-dimensional Palatini action with cosmological te... more We report a new internal gauge symmetry of the n-dimensional Palatini action with cosmological term (n > 3) that is the generalization of three-dimensional local translations. This symmetry is obtained through the direct application of the converse of Noether's second theorem on the theory under consideration. We show that diffeomorphisms can be expressed as linear combinations of it and local Lorentz transformations with field-dependent parameters up to terms involving the variational derivatives of the action. As a result, the new internal symmetry together with local Lorentz transformations can be adopted as the fundamental gauge symmetries of general relativity. Although their gauge algebra is open in general, it allows us to recover, without resorting to the equations of motion, the very well-known Lie algebra satisfied by translations and Lorentz transformations in three dimensions. We also report the analog of the new gauge symmetry for the Holst action with cosmological term, finding that it explicitly depends on the Immirzi parameter. The same result concerning its relation to diffeomorphisms and the open character of the gauge algebra also hold in this case. Finally, we consider the non-minimal coupling of a scalar field to gravity in n dimensions and establish that the new gauge symmetry is affected by this matter field. Our results indicate that general relativity in dimension greater than three can be thought of as a gauge theory.
Classical and Quantum Gravity, 2016
BF gravity comprises all the formulations of gravity that are based on deformations of BF theory.... more BF gravity comprises all the formulations of gravity that are based on deformations of BF theory. Such deformations consist of either constraints or potential terms added to the topological BF action that turn some of the gauge degrees of freedom into physical ones, particularly giving rise to general relativity. The BF formulations have provided new and deep insights into many classical and quantum aspects of the gravitational field, setting the foundations for the approach to quantum gravity known as spinfoam models. In this review, we present a self-contained and unified treatment of the BF formulations of Ddimensional general relativity and other related models, focusing on the classical aspects of them and including some new results.
Physical Review D, 2016
We present a new BF-type action for complex general relativity with or without a cosmological con... more We present a new BF-type action for complex general relativity with or without a cosmological constant resembling Plebanski's action, which depends on an SO(3,C) connection, a set of 2-forms, a symmetric matrix, and a 4-form. However, it differs from the Plebanski formulation in the way that the symmetric matrix enters into the action. The advantage of this fact is twofold. First, as compared to Plebanski's action, the symmetric matrix can now be integrated out, which leads to a pure BFtype action principle for general relativity; the canonical analysis of the new action then shows that it has the same phase space of the Ashtekar formalism up to a canonical transformation induced by a topological term. Second, a particular choice of the parameters involved in the formulation produces a BF-type action principle describing conformally anti-self-dual gravity. Therefore, the new action unifies both general relativity and anti-self-dual gravity.
mBio, Jan 28, 2015
CcrM is an orphan DNA methyltransferase nearly universally conserved in a vast group of Alphaprot... more CcrM is an orphan DNA methyltransferase nearly universally conserved in a vast group of Alphaproteobacteria. In Caulobacter crescentus, it controls the expression of key genes involved in the regulation of the cell cycle and cell division. Here, we demonstrate, using an experimental evolution approach, that C. crescentus can significantly compensate, through easily accessible genetic changes like point mutations, the severe loss in fitness due to the absence of CcrM, quickly improving its growth rate and cell morphology in rich medium. By analyzing the compensatory mutations genome-wide in 12 clones sampled from independent ΔccrM populations evolved for ~300 generations, we demonstrated that each of the twelve clones carried at least one mutation that potentially stimulated ftsZ expression, suggesting that the low intracellular levels of FtsZ are the major burden of ΔccrM mutants. In addition, we demonstrate that the phosphoenolpyruvate-carbohydrate phosphotransfer system (PTS) actu...
2014 IEEE 60th Holm Conference on Electrical Contacts (Holm), 2014
Experiments with arcs confined in tubes and Miniature Circuit Breakers - MCBs with gassing walls ... more Experiments with arcs confined in tubes and Miniature Circuit Breakers - MCBs with gassing walls of different engineering plastic compounds were carried out. In the first part of the investigation the arc chamber consisted of small tubes of the different materials. The arc-current source was a damped capacity bank with high charging voltages. For the second part of the investigation customary 32 A MCBs were used with gassing inserts of the different materials, which replaced the standard gassing polymer. The arc currents were provided from a power transformer connected to the 20 kV 50 Hz network. The influence of gassing effects of 8 different plastic compounds and Al2O3 ceramic (as reference) on arcs with amplitudes of 1 kA and 3 kA (tubes) and of 1 kA (MCBs) was investigated. Arc signals of current and voltage and of pressure (for the setup with polymer tubes) were recorded. The paper presents the comparison of the measured values for the two different experimental setups and arc-currents. The correlation of the experimental results regarding the polymer influence on the arc is discussed.
Physical Review D, 2015
We report a new class of SO(3, C) and diffeomorphism invariant formulations for general relativit... more We report a new class of SO(3, C) and diffeomorphism invariant formulations for general relativity with either a vanishing or a nonvanishing cosmological constant, which depends functionally on a SO(3, C) gauge connection and a complex-valued 4-form via a holomorphic function of the trace of a symmetric 3 × 3 matrix that is constructed from these variables. We present two members of this class, one of which results from the implementation of a method for obtaining action principles belonging to the class. For the case of a nonvanishing cosmological constant, we solve for the complex-valued 4-form and get pure connection action principles. We perform the canonical analysis of the class. The analysis shows that only the Hamiltonian constraint is modified with respect to the Ashtekar formulation and that the members of the class have two physical degrees of freedom per space point.
IECON'03. 29th Annual Conference of the IEEE Industrial Electronics Society (IEEE Cat. No.03CH37468)
... [5] Tepper J. Sebastian; Dixon, Juan W.; Venegas, Gustavo and Moran, Luis .4 Simple Frequenc... more ... [5] Tepper J. Sebastian; Dixon, Juan W.; Venegas, Gustavo and Moran, Luis .4 Simple Frequency-Independent Method for Calculating the Reactive and Harmonic Current in a Nonlinear Load; IEEE Transactions on Industrial Electronics, Vol. 43, No. 6, pp. ...
IECON'03. 29th Annual Conference of the IEEE Industrial Electronics Society (IEEE Cat. No.03CH37468)
This paper presents a method for the calculation of conducted differential mode EMI disturbances ... more This paper presents a method for the calculation of conducted differential mode EMI disturbances produced by switched power inverters. The complex geometry and the wide range of time constants involved, make the simulation of conducted disturbances in such systems a complex matter. The features of the proposed method are shown in the paper by comparing simulation results with experimental results
IECON'03. 29th Annual Conference of the IEEE Industrial Electronics Society (IEEE Cat. No.03CH37468)
Although most of the power converters are currently designed to operate by using a constant switc... more Although most of the power converters are currently designed to operate by using a constant switching frequency and a variable duty-cycle, some attempts were made in order to verify the effect of modulating the switching frequency [F. Lin et al., 1992] and how this modulation affected the power converters EMI emissions. As known, spread spectrum clock generation (SSCG) modulates the
Medicina, 2008
Cardiovascular manifestations of hyperthyroidism are frequent and sometimes are relevant in the c... more Cardiovascular manifestations of hyperthyroidism are frequent and sometimes are relevant in the clinical picture. Usually an hyperdynamic circulatory state hallmarks the disease with low peripheral resistance, increased intravascular volume and cardiac output. However, right chamber dilatation with tricuspid valve regurgitation and cardiac failure are unusual. We present the case of a young woman with Graves-Basedow disease without cardiovascular history who complained about palpitations, peripheral edemas, weight loss and fever. The clinical findings were tachycardia with irregular pulse, right heart failure and regurgitant tricuspid murmur that increased with inspiration. The chest radiograph and the echocardiogram showed right ventricular dilatation and severe tricuspid regurgitation without pulmonary hypertension. The treatment with propranolol, corticosteroids and diuretics was successful. The patient was asymptomatic with sinus rhythm. We discuss the effects of thyroidal hormo...
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Papers by Diego Pedro Gonzalez