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On the Second-Order Asymptotics of the Hoeffding Test and Other Divergence Tests
Get PDFConsider a composite hypothesis testing problem where the test has access to the null hypothesis P but not to the alternative hypothesis Q. The generalized likelihood-ratio test (GLRT) for this problem is the Hoeffding test, which accepts P if the Kullback-Leibler (KL) divergence between the empirical distribution of Zn and P is below some threshold. This paper proposes a generalization of the Hoeffding test, termed divergence test, for which the KL divergence is replaced by an arbitrary divergence. For this test, the first and second-order terms of the type-II error probability for a fixed type-I error probability are characterized and compared with the error terms of the Neyman-Pearson test, which is the optimal test when both P and Q are known. It is demonstrated that, irrespective of the divergence, divergence tests achieve the first-order term of the Neyman-Pearson test. In contrast, the second-order term of divergence tests is strictly worse than that of the Neyman-Pearson test. It is further demonstrated that divergence tests with an invariant divergence achieve the same second-order term as the Hoeffding test, but divergence tests with a non-invariant divergence may outperform the Hoeffding test for some alternative hypotheses Q. This implies that the GLRT may have a second-order asymptotic performance that is strictly suboptimal.This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program under Grant 714161. The work of Jithin Ravi was supported in part by the Science and Engineering Research Board (SERB) under the Start-Up Research Grant SRG/2022/001393 and in part by Indian Institute of Technology (IIT) Kharagpur under the Faculty Start-Up Research Grant (FSRG). The work of Tobias Koch was supported in part by the Spanish Ministerio de Ciencia e Innovación under Grant PID2020-116683GB-C21/AEI/10.13039/501100011033 and in part by the Comunidad de Madrid under Grant TEC-2024/COM-8
Resource allocation exploiting reflective surfaces to minimize the outage probability in VLC
Get PDFVisible light communication (VLC) is a technology that complements radio frequency (RF) to fulfill the ever-increasing demand for wireless data traffic. The ubiquity of light-emitting diodes (LEDs), exploited as transmitters, increases the VLC market penetration and positions it as one of the most promising technologies to alleviate the spectrum scarcity of RF. However, VLC deployment is hindered by blockage causing connectivity outages in the presence of obstacles. Recently, optical reconfigurable intelligent surfaces (ORISs) have been considered to mitigate this problem. While prior works exploit ORISs for data or secrecy rate maximization, this paper studies the optimal placement of mirrors and ORISs, and the LED power allocation, for jointly minimizing the outage probability while keeping the lighting standards. We describe an optimal outage minimization framework called JointMinOut and present solvable heuristics. We provide extensive numerical results and show that the use of ORISs may reduce the outage probability by up to 67% with respect to a no-mirror scenario and provide a gain of hundreds of kbit/J in optical energy efficiency with respect to the presented benchmark.This work has been partially funded by project PID2023-147305OB-C31 (SOFIA-AIR) by MCIN/ AEI/10.13039/501100011033/ERDF, UE, and by project TED2021-129869B-I00 funded by MI-CIU/AEI/10.13039/501100011033 and European Union Next Generation EU/PRTR. Borja Genoves Guzman has received funding from the European Union under the Marie Skłodowska-Curie grant agreement No 101061853, and M. Morales Cespedes from Ramón y Cajal grant RYC2022-036053-I, MICIU/AEI/10.13039/501100011033 and FSE+
A Generative Model Approach for LiDAR-Based Classification and Ego Vehicle Localization Using Dynamic Bayesian Networks
Get PDFThis article belongs to the Special Issue Mobile Robots and Autonomous Vehicles with Clean and Cognitive MobilityOur work presents a robust framework for classifying static and dynamic tracks and localizing an ego vehicle in dynamic environments using LiDAR data. Our methodology leverages generative models, specifically Dynamic Bayesian Networks (DBNs), interaction dictionaries, and a Markov Jump Particle Filter (MJPF), to accurately classify objects within LiDAR point clouds and localize the ego vehicle without relying on external odometry data during testing. The classification phase effectively distinguishes between static and dynamic objects with high accuracy, achieving an F1 score of 91%. The localization phase utilizes a combined dictionary approach, integrating multiple static landmarks to improve robustness, particularly during simultaneous multi-track observations and no-observation intervals. Experimental results validate the efficacy of our proposed approach in enhancing localization accuracy and maintaining consistency in diverse scenariosThis research was partially funded by the European Union’s Horizon Europe research and innovation programme under the Grant Agreement No. 101121134 (B-prepared), and by the European Union—NextGenerationEU and by the Ministry of University and Research (MUR), National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.5, project “RAISE—Robotics and Al for Socio-economic Empowerment” (ECS00000035). This research was also funded by the Spanish Government under Grants: PID2021-124335OB-C21, PID2022-140554OB-C32, TED2021-129485B-C44 and PDC2022-133684-C31
La imagen de estasis predice el riesgo de eventos cardioembólicos tras el infarto agudo de miocardio: el estudio ISBITAMI = Stasis imaging predicts the risk of cardioembolic events related to acute myocardial infarction: the ISBITAMI study
Get PDFIntroducción y objetivos: Tras el infarto agudo de miocardio con elevación del segmento ST (IAMCEST), los biomarcadores por imagen pueden ser útiles para guiar la anticoagulación oral en la prevención primaria de la cardioembolia. Nuestro objetivo es probar la eficacia de la imagen de estasis intraventricular como predictora del riesgo cardioembólico después de un IAMCEST.
Métodos: Se diseñó un estudio clínico prospectivo, Imaging Silent Brain Infarct in Acute Myocardial Infarction (ISBITAMI), que incluyó a pacientes con un primer IAMCEST y fracción de eyección del ventrículo izquierdo ≤ 45%, sin fibrilación auricular, para evaluar el desempeño de las métricas de estasis en la predicción de la cardioembolia. En la inclusión, se obtuvieron imágenes de estasis por ultrasonido, seguidas de resonancia magnética cardiaca y cerebral en 2 visitas tras 1 semana y 6 meses. Usando los mapas de estasis, calculamos el tiempo de residencia promedio, RT, de la sangre dentro del VI y evaluamos su eficacia para predecir el objetivo primario. El strain apical longitudinal en los 4 segmentos apicales se cuantificó mediante speckle tracking.
Resultados: Un total de 66 pacientes completaron el periodo de seguimiento. De ellos, 17 pacientes sufrieron 1 o más eventos: 3 ictus, 5 infartos cerebrales silentes y 13 trombosis murales. No se observaron embolias sistémicas. El RT (OR = 3,73; IC95%,1,75-7,97; p < 0,001) y el strain apical (OR = 1,47; IC95%, 1,13-1,92; p = 0,004) mostraron un valor pronóstico complementario. El modelo bivariado mostró un índice c = 0,86 (IC95%, 0,73-0,95), un valor predictivo negativo de 1,00 (IC95%, 0,94-1,0) y un valor predictivo positivo de 0,45 (IC95%, 0,37-0,77). Las métricas convencionales tuvieron un valor predictivo limitado.
Conclusiones: En pacientes con IAMCEST y disfunción sistólica del VI en ritmo sinusal, el riesgo de cardioembolia puede estimarse usando ecocardiografía y combinando imágenes de estasis y deformación. Registrado en ClinicalTrials.gov (NCT02917213).Introduction and objectives: In the setting of ST-segment elevation myocardial infarction (STEMI), imaging-based biomarkers could be useful for guiding oral anticoagulation to prevent cardioembolism. Our objective was to test the efficacy of intraventricular blood stasis imaging for predicting a composite primary endpoint of cardioembolic risk during the first 6 months after STEMI.
Methods: We designed a prospective clinical study, Imaging Silent Brain Infarct in Acute Myocardial Infarction (ISBITAMI), including patients with a first STEMI, an ejection fraction ≤ 45% and without atrial fibrillation to assess the performance of stasis metrics to predict cardioembolism. Patients underwent ultrasound-based stasis imaging at enrollment followed by heart and brain magnetic resonance at 1-week and 6-month visits. From the stasis maps, we calculated the average residence time, RT, of blood inside the left ventricle and assessed its performance to predict the primary endpoint. The longitudinal strain of the 4 apical segments was quantified by speckle tracking.
Results: A total of 66 patients were assigned to the primary endpoint. Of them, 17 patients had 1 or more events: 3 strokes, 5 silent brain infarctions, and 13 mural thromboses. No systemic embolisms were observed. RT (OR, 3.73; 95%CI, 1.75-7.9; P < .001) and apical strain (OR, 1.47; 95%CI, 1.13-1.92; P = .004) showed complementary prognostic value. The bivariate model showed a c-index = 0.86 (95%CI, 0.73-0.95), a negative predictive value of 1.00 (95%CI, 0.94-1.00), and positive predictive value of 0.45 (95%CI, 0.37-0.77). The results were confirmed in a multiple imputation sensitivity analysis. Conventional ultrasound-based metrics were of limited predictive value.
Conclusions: In patients with STEMI and left ventricular systolic dysfunction in sinus rhythm, the risk of cardioembolism may be assessed by echocardiography by combining stasis and strain imaging. Registered at ClinicalTrials.gov (NCT02917213).Este estudio ha sido financiado por el Instituto de Salud Carlos III (PI15/02211-ISBITAMI y DTS/1900063 -ISBIFLOW), la Comunidad de Madrid (Synergy Grant: Y2018/BIO-4858 PREFI-CM) y por el Fondo Europeo de Desarrollo Regional. JCdA recibió apoyo parcial de las subvenciones NIH R01HL158667 y NIH R01HL160024
Economic nationalism in Interwar Turkey: policies, domestic market integration and ethnic trade networks
Get PDFMención Internacional en el título de doctorThe first half of the twentieth century was a period of profound political and economic transformations in Central and Eastern Europe (CEE) as well as the Near East (NE). Four empires, ruled by Habsburg-Lorraine, Romanov, Hohenzollern and Ottoman dynasties, collapsed in the Eurasian crossroads and were replaced by smaller nation-states (Hobsbawm, 1995, p. 139; Lampe, 2014, p. 9; Toprak, 2019, p. 488). One of the central questions for these states was the direction of trade policy within new borders. Concerns over political independence following the Balkan Wars and the First World War (WWI) made economic nationalism an integral part of the nation-building processes in both young and newly enlarged agrarian nation-states (Abdelal, 2002, pp. 902–913; Teichova, 2008, p. 893). Domestic markets and commercial networks saw significant changes. Yet, economic nationalist policies of these nation-states exhibited a dichotomous nature: they were defensive of national economic interests by protecting and integrating the domestic markets within new borders, while simultaneously adopting exclusionary policies toward indigenous minority group traders (Kofman, 1997, p. 205). Interwar Turkey was no exception in this regard.
This thesis investigates the impact of economic nationalism on commodity markets in Interwar Turkey, drawing on two novel historical datasets constructed from primary and secondary sources. It adopts a comparative approach rather than focusing solely on the case of Interwar Turkey. In doing so, this thesis provides a general framework to analyze the impact of economic nationalism in agrarian nation-states during the interwar period. The comparative analysis is extended empirically thanks to Nikolaus Wolf’s generous sharing of his dataset on commodity prices in Interwar Poland (Trenkler and Wolf, 2005), another young agrarian nation-state of the era. Parallels between economic policies shaped by economic nationalism in Turkey and Poland further enrich the historical analysis. Overall, this thesis challenges the existing economic history literature and uncovers the unintended consequences of economic nationalism through new empirical evidence.Programa de Doctorado en Historia Económica por la Universidad Carlos III de Madrid; la Universidad de Barcelona y la Universitat de València (Estudi General)Presidente: Sergio Espuelas Barroso.- Secretario: Stefan Nikolic.- Vocal: Seven Agi
Essays on Technological and Monetary Policy Shocks
Get PDFThis thesis is an attempt to contribute to the broad and active line of research on the estimation and effects of technological and monetary policy shocks, as highlighted by Ramey (2016). In different ways, each chapter examines the role of these shocks in shaping macroeconomic outcomes, particularly focusing on open economy dynamics, investment-specific technology innovations, and green technology. By developing new identification strategies and addressing important measurement challenges, the chapters provide fresh insights into how shocks propagate and influence key macroeconomic variables, enriching our understanding of causal relationships in the macroeconomy.
The first chapter explores the ”exchange rate puzzle” in Brazil, where contractionary monetary policy often leads, counterintuitively, to a depreciation of the domestic currency. I find that default risk plays a crucial role in this phenomenon: unanticipated monetary tightening associated with a simultaneous increase in perceived default risk leads to currency depreciation. Conversely, when default risk surprises are smaller, monetary tightening results in appreciation and capital outflows. Using a small open economy model augmented with sovereign risk and high-frequency data from credit default swaps, the chapter shows that accounting for default risk helps resolve the puzzle and offers new perspectives on monetary policy transmission in emerging markets.
The second and third chapters delve into technology-related shocks. The second chapter reexamines the role of investment-specific technology (IST) shocks, demonstrating that standard identification approaches confound the effects of oil and food price fluctuations. After adjusting for these commodityrelated influences through a refined structural VAR and a DSGE model with a commodity sector, IST shocks are found to cause declining price levels, prompt increases in GDP and investment, and a delayed rise in consumption, with a reduced contribution to GDP and consumption variance.
The third chapter, co-authored with Andrey Ramos, focuses on green technology news shocks. Using data on green patents and a Bayesian VAR approach, we decompose news technological surprises into a common technology component and a green-specific component. The green-specific news shock leads to inflationary pressures and stock price declines, suggesting that expectations about stricter future environmental regulations are priced in by the market. Together, these chapters advance our understanding of how different types of technology shocks affect macroeconomic dynamics and sectoral transitions.Programa de Doctorado en Economía por la Universidad Carlos III de MadridPresidente: Johannes Pfeifer.- Secretario: Hernán Daniel Seoane Bernadaz.- Vocal: Sebastian Fanell
Un acercamiento a los narradores españoles nacidos en los años 1960 desde el punto de vista de la generación literaria
Get PDFPrograma de Doctorado en Humanidades por la Universidad Carlos III de MadridPresidente: Epícteto José Díaz Navarro.- Secretario: David Becerra Mayor.- Vocal: María Carmen Luna Sellé
A comprehensive study of MIL-88a as a key component of hybrid polymer electrolytes for H2 fuel cells
Get PDFIn this work, an electrochemical study of the iron fumarate metal-organic framework structure MIL-88a was carried out. This MOF exhibits an exceptional characteristic: it alters the parameters of its crystal lattice in response to temperature variations and the specific guest molecules present. Through impedance spectroscopy, we investigated how guest molecules within the pores of MIL-88a influence the material's ionic conductivity and its responsiveness to changing environmental conditions. Based on the data obtained, hybrid membranes based on sulfonated multiblock copolymers of polysulfone and polyphenylsulfone (SPES) doped with MIL-88a were prepared. The distribution of crystallites in the membrane was assessed by using scanning electron microscopy. It was found that crystallites agglomerates reduce the tensile strength of the membrane from 87 to 69 MPa, and from 56 to 42 MPa in the dry and wet forms, respectively. The presence of this MOF doubles the water absorption of the hybrid membranes compared to the pure one, resulting in an improvement of their ionic conductivity from 15.8 to 26.5 mS/cm at 80 °C. Hybrid membranes show a high maximum power density (1040 mWcm-2)in the fuel single cell test that is comparable to that obtained for commercial perfluoro-sulfonic acid PEMs such as Nafion®.This work has been supported by Agencia Estatal de Investigación (AEI) with the project TED2021-132092B–C22 and Ministry of Science and Higher Education of the Russian Federation (State assignment in the field of scientific activity, № FENW-2023-0019)
User Empowerment in Adaptive Video Streaming over Best-Effort Networks
Get PDFMención Internacional en el título de doctorVideo streaming is not only the largest source of Internet traffic but also one of the most economically significant industries, particularly in its adaptive form, where content is delivered in multiple quality levels via the hypertext transfer protocol (HTTP). Users purchase streaming services from streaming platforms (SPs) and network access from Internet service providers (ISPs), both of which strive to enhance user satisfaction, known as quality of experience (QoE), through contrasting methods. QoE is crucial for the ecosystem’s economy and technological advancements, but its subjective nature complicates measurement and application. Consequently, easier-to-use yet less accurate QoE proxies, termed QoE models, become prevalent.
Service providers, particularly SPs, increasingly incorporate active user involvement to boost QoE. This trend, known as user empowerment, offers users active opportunities to enhance their streaming experience. It targets increasing QoE for those who are willing to invest effort, while not impacting those who prefer a passive role. Because user participation requires balancing effort and reward, empowerment strategies must manage this trade-off effectively while ensuring simplicity and privacy. From the providers’ viewpoint, these strategies serve as extensions of core services, necessitating cost-effectiveness and easy integration. This approach enhances QoE and gives engaged users more control, fostering trust, loyalty, and a competitive advantage for the platform.
Currently, user empowerment techniques in video streaming are still nascent. This thesis aims to bridge the gap in user empowerment within adaptive video streaming, focusing on enhancing QoE through active engagement with SPs and ISPs. The work presents four key contributions: 1) A holistic exploration of the video streaming landscape, emphasizing adaptive streaming of long-form videos over current Internet architecture, while reviewing and classifying state-of-the-art methods and identifying promising development directions. 2) A method for creating personalized QoE models by engaging users in brief assessment sessions, resulting in significant QoE improvements through active learning. 3) A novel mechanism for in-band QoE communication from users to ISPs, utilizing the SP’s client interface for QoE estimation and transmission, supported by a prototype demonstrating its feasibility. 4) An evaluation of shortcomings in QoE practices and models, providing guidelines for improvement.This work has been supported by IMDEA Networks InstitutePresidenta: María Torres Vega. - Vocal: Maria Giuseppina Martini. - Secretario: Ignacio de Castro Arriba
No evidence for association between pupil size and fluid intelligence among either children or adults
Get PDFRecent studies have investigated resting-state, or baseline, pupil size as a general measure of cognitive abilities, based on the earlier finding that larger pupils might be predictive of higher general intelligence or working memory capacity. However, evidence for such relationships has been mixed, and all previous studies thus far have focused on adult samples. The present study adds to this debate by examining the correlation between fluid intelligence and baseline pupil size in a sample of both children (10 years old) and adults (their parents). Importantly, our sample is representative in terms of socioeconomic background, which was not the case in previous studies, thus addressing concerns about sample selection and variability. We did not find evidence for a relationship of fluid intelligence with baseline pupil size or with pupil-size variability for either children or adults. Therefore, our results do not replicate the relationship between cognitive abilities and baseline pupil size as reported in previous research.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The research leading to these results was funded by the European Research Council (ERC), under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 758600)