Search

This paper examines the potential impact of different US economic sanctions policies on Venezuelan migration flows. I consider three possible departures from the current status quo in which selected oil companies are permitted to conduct transactions with Venezuela's state-owned oil sector: a return to maximum pressure, characterized by intensive use of secondary sanctions, a more limited tightening that would revoke only the current Chevron license, and a complete lifting of economic sanctions. I find that sanctions significantly influence migration patterns by disrupting oil revenues, which fund imports critical to productivity in the non-oil sector. Reimposing maximum pressure sanctions would lead to an estimated one million additional Venezuelans emigrating over the next five years compared to a baseline scenario of no economic sanctions. If the US aims to address the Venezuelan migrant crisis effectively, a policy of engagement and lifting economic sanctions appears more likely to stabilize migration flows than a return to maximum pressure strategies.

Optical detection of magnetic resonance using quantum spin sensors (QSS) provides a spatially local and sensitive technique to probe spin dynamics in magnets. However, its utility as a probe of antiferromagnetic resonance (AFMR), wherein the characteristic resonant frequencies substantially exceed the QSS probing frequency, remains an open question. Here, using the nitrogen-vacancy center in diamond as a QSS, we report the first experimental demonstration of optically detected AFMR in layered van der Waals antiferromagnets up to frequencies of 24 GHz, significantly higher than the sensor's spin resonance frequency of 2.87 GHz. To achieve this, we leverage the enhancement of the QSS spin relaxation rate due to low-frequency magnetic field fluctuations that arise from collective late-time dynamics of finite-wavevector magnons excited by the driven uniform AFMR mode. Using optically detected AFMR, we first characterize the temperature and magnetic field dependence on the AFMR modes, which shed light on the intrinsic exchange fields and magnetic anisotropies. Second, we exploit the highly localized sensitivity of the QSS to demonstrate efficient magnon transport over tens of micrometers. Finally, we find that optical detection efficiency in fact increases with increasing frequency, enabling broadband detection of magnetization dynamics. Our work showcases the dual capabilities of QSS as detectors of both high frequency magnetization dynamics and magnon transport, paving the way for understanding and controlling magnetism in Neel states in antiferromagnets.

Social Robots need to be safe and reliable to share their space with humans. This paper reports on the first results of a research project that aims to create more safe and reliable, intelligent autonomous robots by investigating the implications and interactions between cybersecurity and safety. We propose creating a robotic intrusion prevention system (RIPS) that follows a novel approach to detect and mitigate intrusions in cognitive social robot systems and other cyber-physical systems. The RIPS detects threats at the robotic communication level and enables mitigation of the cyber-physical threats by using System Modes to define what part of the robotic system reduces or limits its functionality while the system is compromised. We demonstrate the validity of our approach by applying it to a cognitive architecture running in a real social robot that preserves the privacy and safety of humans while facing several cyber attack situations.

The growth of distributed renewable energy in the electrical grid presents challenges to its stability and quality. To address this at the local level, flexibility energy strategies emerge as an innovative technique. However, managing these strategies in residential areas becomes complex due to the unique characteristics of each prosumer. A major challenge lies in managing communication among diverse devices with different protocols. To address these issues, a comprehensive framework is designed and implemented to facilitate prosumers' integration in flexibility strategies, addressing communication at various levels. The effectiveness of the proposed framework is demonstrated through its implementation in a real smart home environment with diverse devices. The framework enables seamless integration and communication between IoT devices and IEC 61,850-compliant power devices. This research presents a novel approach to address the challenges of managing flexibility strategies in residential areas, providing a practical solution for prosumers to actively participate in optimizing energy consumption and enhancing the stability and quality of the electricity system amidst the growing integration of distributed renewable energy.

This paper introduces an innovative dataset specifically crafted for challenging agricultural settings (a greenhouse), where achieving precise localization is of paramount importance. The dataset was gathered using a mobile platform equipped with a set of sensors typically used in mobile robots, as it was moved through all the corridors of a typical Mediterranean greenhouse featuring tomato crop. This dataset presents a unique opportunity for constructing detailed 3D models of plants in such indoor-like space, with potential applications such as robotized spraying. For the first time to the best knowledge of authors, a dataset suitable to put at test Simultaneous Localization and Mapping (SLAM) methods is presented in a greenhouse environment, which poses unique challenges. The suitability of the dataset for such goal is assessed by presenting SLAM results with state-of-the-art algorithms. The dataset is available online in \url{https://arm.ual.es/arm-group/dataset-greenhouse-2024/}., Comment: 29 pages, 15 figures

Venezuela has suffered three economic catastrophes since independence: one each in the nineteenth, twentieth, and twenty-first centuries. Prominent explanations for this trilogy point to the interaction of class conflict and resource dependence. We turn attention to intra-class conflict, arguing that the most destructive policy choices stemmed not from the rich defending themselves against the masses but rather from pitched battles among elites. Others posit that Venezuelan political institutions failed to sustain growth because they were insufficiently inclusive; we suggest in addition that they inadequately mediated intra-elite conflict., Comment: 28 pages, 3 figures

This article reviews recent advances in addressing empirical identification issues in cross-country and country-level studies and their implications for the identification of the effectiveness and consequences of economic sanctions. I argue that, given the difficulties in assessing causal relationships in cross-national data, country-level case studies can serve as a useful and informative complement to cross-national regression studies. However, I also warn that case studies pose a set of additional potential empirical pitfalls which can obfuscate rather than clarify the identification of causal mechanisms at work. Therefore, the most sensible way to read case study evidence is as a complement rather than as a substitute to cross-national research.

The analysis of numerical simulations describing the collapse of capillary cavities reveals that the jets originated from the bursting of bubbles are driven by the condition that the dimensionless liquid flow rate per unit length directed towards the axis of symmetry, $q_\infty$, remains nearly constant in time. This observation, which is justified in physical terms because liquid inertia prevents appreciable changes in $q_\infty$ during the short time scale characterizing the jet ejection process, together with the fact that bubble bursting jets are produced from the bottom of a conical cavity, justify the purely inertial scalings for the jet width and velocity found here, $r_{jet}\propto\sqrt{q_\infty\tau}$ and $v_{jet}\propto \sqrt{q_\infty/\tau}$, with $\tau$ indicating the dimensionless time after the jet is ejected, a result which notably differs from the common belief that the jet width and velocity follow the inertio-capillary scaling $r_{jet}\propto \tau^{2/3}$ and $v_{jet}\propto \tau^{-1/3}$. Our description reproduces the time evolution of the jet width and velocity for over three decades in time, obtaining good agreement with numerical simulations from the instant of jet inception until the jet width is comparable to that of the initial bubble., Comment: 15 pages, 10 figures. Figures are revised and properly referenced (v100323)

Motivated by the results in Gordillo and Blanco-Rodriguez, 'Bubble bursting jets are driven by the purely inertial collapse of gas cavities', \emph{Phys. Rev. Lett., Submitted} (2023) \cite{PRL2023}, where it is found that bubble bursting jets are driven by a purely inertial mechanism, here we present a study on the dynamics of the jets produced by the collapse of gas cavities of generic shape when the implosion is forced by a far field boundary condition expressing that the flow rate per unit length, $q_\infty$, remains constant in time. Making use of theory and of numerical simulations, we first analyze the case of a conical bubble with a half-opening angle $\beta$ when the value of $q_\infty$ is fixed to a constant, finding that this type of jets converge towards a purely inertial $\beta$-dependent self-similar solution of the equations in which the jet width and velocity are respectively given, in the limit $\beta\ll 1$, by $r_{jet}\approx 2.25\tan\beta\sqrt{q_\infty\tau}$ and $v_{jet}\approx 3 q_\infty/(2\tan\beta\sqrt{q_\infty\tau})$ respectively, with $\tau$ indicating the dimensionless time after the jet is ejected. For the case of parabolic cavities with a dimensionless radius of curvature at the plane of symmetry $r_c$ our theory predicts that $r_{jet}\propto \left(2 r_c\right)^{-1/2}\left(q_\infty \tau\right)^{3/4}$ and $v_{jet}\propto q_\infty \left(2r_c\right)^{1/2} \left(q_\infty\tau\right)^{-3/4}$, a result which is also in good agreement with numerical simulations. The present results might find applications in the description of the very fast jets, with velocities reaching up to $1000$ m s$^{-1}$, produced after a bubble cavitates very close to a wall and in the quantification of the so-called bazooka effect., Comment: 18 pages, 11 figures

We revisit the results of a recent paper by Equipo Anova, who claim to find evidence of an improvement in Venezuelan imports of food and medicines associated with the adoption of U.S. financial sanctions towards Venezuela in 2017. We show that their results are consequence of data coding errors and questionable methodological choices, including the use an unreasonable functional form that implies a counterfactual of negative imports in the absence of sanctions, the omission of data accounting for four-fifths of the country's food imports at the time of sanctions and incorrect application of regression discontinuity methods. Once these errors are corrected, the evidence of a significant improvement in the level and rate of change in imports of essentials disappears.

Self-localization is a fundamental capability that mobile robot navigation systems integrate to move from one point to another using a map. Thus, any enhancement in localization accuracy is crucial to perform delicate dexterity tasks. This paper describes a new location that maintains several populations of particles using the Monte Carlo Localization (MCL) algorithm, always choosing the best one as the sytems's output. As novelties, our work includes a multi-scale match matching algorithm to create new MCL populations and a metric to determine the most reliable. It also contributes the state-of-the-art implementations, enhancing recovery times from erroneous estimates or unknown initial positions. The proposed method is evaluated in ROS2 in a module fully integrated with Nav2 and compared with the current state-of-the-art Adaptive ACML solution, obtaining good accuracy and recovery times., Comment: Submission for ICRA 2023