43 research outputs found
Structure transfer and consolidation in visual implicit learning
No full textTransfer learning, the re-application of previously learned higher-level regularities to novel input, is a key challenge in cognition. While previous empirical studies investigated human transfer learning in supervised or reinforcement learning for explicit knowledge, it is unknown whether such transfer occurs during naturally more common implicit and unsupervised learning and, if so, how it is related to memory consolidation. We compared the transfer of newly acquired explicit and implicit abstract knowledge during unsupervised learning by extending a visual statistical learning paradigm to a transfer learning context. We found transfer during unsupervised learning, but with important differences depending on the explicitness/implicitness of the acquired knowledge. Observers acquiring explicit knowledge during initial learning could transfer the learned structures immediately. In contrast, observers with the same amount but implicit knowledge showed the opposite effect, a structural interference during transfer. However, with sleep between the learning phases, implicit observers, while still remaining implicit, switched their behavior and showed the same pattern of transfer as explicit observers did. This effect was specific to sleep and not found after non-sleep consolidation. Our results highlight similarities and differences between explicit and implicit learning while acquiring generalizable higher-level knowledge and relying on consolidation for restructuring internal representations
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Pre-Training Leads to a Structural Novelty Effect in Spatial Visual Statistical Learning
No full textWe investigated the influence of structural properties of previously learned stimuli on Spatial Visual Statistical Learning.
Participants (n=170) were first exposed to a stream of scenes containing only one type of regularity (horizontal or vertical pairs), followed by a stream containing both types of regularities. We found that participants performed above chance for the pairs of the first stream (M=54.7%, SE=1.2, p<0.001, BF=91.89) as well as for the novel type of pair of the second stream (M=55.6%, SE=1.9, p=0.005, BF=4.04), but not for the familiar type of pair of the second stream (M=51.5%, SE=2.0, p=0.465, BF=0.11).
This observed novelty effect indicates an interference between the similarly structured pairs in the first and second stream of scenes, suggesting representational overlap of pairs of the same orientation
Spatio-temporal visual statistical learning in context
No full textVisual Statistical Learning (VSL) is classically investigated in a restricted format, either as temporal or spatial VSL, and void of any effect or bias due to context. However, in real-world environments, spatial patterns unfold over time, leading to a fundamental intertwining between spatial and temporal regularities. In addition, their interpretation is heavily influenced by contextual information through internal biases encoded at different scales. Using a novel spatio-temporal VSL setup, we explored this interdependence between time, space, and biases by moving spatially defined patterns in and out of participants' views over time in the presence or absence of occluders. First, we replicated the classical VSL results in such a mixed setup. Next, we obtained evidence that purely temporal statistics can be used for learning spatial patterns through internal inference. Finally, we found that motion-defined and occlusion-related context jointly and strongly modulated which temporal and spatial regularities were automatically learned from the same visual input. Overall, our findings expand the conceptualization of VSL from a mechanistic recorder of low-level spatial and temporal co-occurrence statistics of single visual elements to a complex interpretive process that integrates low-level spatio-temporal information with higher-level internal biases to infer the general underlying structure of the environment
Pre-Training Leads to a Structural Novelty Effect in Spatial Visual Statistical Learning
No full textExploiting PUF Variation to Detect Fault Injection Attacks
No full textThe massive deployment of Internet of Things (IoT) devices makes them vulnerable against physical tampering attacks, such as fault injection. These kind of hardware attacks are very popular as they typically do not require complex equipment or high expertise. Hence, it is important that IoT devices are protected against them. In this work, we present a novel fault injection attack detector with high flexibility and low overhead. Our solution is based on the reuse of a security primitive used in many IoT devices, i.e., ring oscillator (RO) physically unclonable function (PUF). Our results show that we obtain a high detection effectiveness and no false alarms against most popular fault injection attacks based on voltage and clock manipulations.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Computer EngineeringQuantum & Computer Engineerin
A computational glance at organometallic cyclizations and coupling reactions
No full text210 p.Organometallic chemistry is one of the main research topics in chemical science.Nowadays, organometallic reactions are the subject of intensive theoretical investigations.However, in many cases, only joint experimental and theoretical effortscould reveal the answers what we are looking for.The fruits of such experimental and theoretical co-operations will be presentedhere. In this work, we are going to deal with homogeneous organometallic catalysisusing computational chemical tools. Particularly, DFT study of palladium andgold-catalyzed reactions and special carbometalations will be described.Chapter 1 gives an introductory overview of organometallic chemistry andcatalysis in general using a historical perspective. It covers the 9 thousand yearshistory of catalysis from 7000 BC (the earliest concrete evidence of man-made fermentation/biocatalysis) through several milestones (Libavius, Berzelius etc.) upto the present days of organometallic chemistry.Chapter 2 is a short methodological summary and intended to shed some lighton the theoretical foundations of the applied quantum chemical tools, but it is neithercomplete, nor deep, just enough to scratch the surface and give insight into thecomplexity of the theory.The results of our calculations presented in three separate chapters,(Chapter 3, 4 and 5) in each of which the calculations discussed along with theviiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fisercorresponding experimental findings of our collaborators and/or other scientists.Chapter 3 describe specific issues of palladium-catalyzed reactions. In this partof the work, palladium(II)-catalyzed dynamic kinetic asymmetric C¿P couplingfor the asymmetric synthesis of QUINAP and other atropos P,N-ligands is discussedand the reaction investigated at the M06/6-31+G(d,p)/SDD//B3LYP/6-31G(d)/LANL2DZ level of theory. The computational results along with xperimentalevidences collected by our collaborators allowed to propose a mechanismbased on the formation of cationic oxidative addition intermediates which underthe reaction conditions, undergo a fast interconversion (Figure 0.0.1). Coordinationof the isoquinoline N atom to Pd is essential to facilitate this process.Figure 0.0.1: Proposed Mechanism for the Epimerization of DiastereomericOxidative Addition Intermediates (OAI and OAI¿).The calculations also show that the energy requirements for a dynamic kineticprocess are met, since the fast equilibrating palladacyclic intermediates evolve throughixSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fiserdiastereomeric transmetalation steps of very large energy difference. The easinessof the final reductive elimination ensures the irreversibility of the process.Chapter 4 can be divided into two parts in which gold(I)-catalyzed reactionsare studied.In the first section, the tandem gold(I)-catalyzed rearrangement/Nazarov reactionof propargylic ester derivatives studied in deeply computationally and thecalculations revealed the details of the reaction mechanism (Figure 0.0.2) whichallowed us to evaluate energetically the influence of the substrate structures on thereaction rate and on the regio- and stereoselectivity.Figure 0.0.2: Reaction Mechanism. Top: Acetate Rearrangement in the InitialSteps of the Mechanism. Bottom: Cyclization Step from the pre-Nazarovcyclization complex III and Protodeauration. Gibbs Free Energy Changes(¿G) and Barrier Heights (¿Gz) are Given in kcal/mol.xSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserIn the second section, gold(I)-catalyzed cycloisomerizations calculated (Figure0.0.3). The calculations showed that with both types of substrates, the oxyaurationstep has a low barrier or almost no barrier at all when it involves the internalposition of a terminal triple bond, resulting in a 5-exo-dig process. In contrast,the 6-endo-dig mechanism is always favoured with substituted alkynes. The preferencebeing purely geometrical and irrespective of the type of substitution, thusproviding either ß-enaminones or their reduced equivalents, ß-amino ketones, ina robust, reliable, and convenient way.Figure 0.0.3: Transition State Structures and the Corresponding BarrierHeights (¿Gz, in kcal/mol) for Terminal and Internal Alkynes.xiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserChapter 5 is a systematical study of intramolecular metal catalyzed cyclizations.Group 10 alkyl metalations are studied systematically by means of DFT calculationsand based on the results the extension of the Baldwin¿s rules for metal catalyzedring closure reactions is proposed (Figure 0.0.4).Figure 0.0.4: Studied Group 10 Alkyl Metalations.An intuitive summary of the qualitative results created and the results couldserve as a guide to explore not yet described cyclization processes based on the accessiblecomputed activation energies and the qualitative comparison of the preferences.Our manuscripts published in connection with the topics discussed in the thesiscan be found in the Appendix.xiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserA Computational Glance at Organometallic Cyclizationsand Coupling ReactionsAbstractLa química organometálica es uno de los campos más activos de investigación enciencias químicas. Hoy en día, las reacciones organometálicas son sujeto de numerosasinvestigaciones teóricas. Sin embargo, en muchos casos, sólo los esfuerzosconjuntos teóricos y experimentales son capaces de encontrar las respuestasque buscamos. En este trabajo se presentan los frutos de tales colaboracionesexperimentales/teóricas. Hemos empleado herramientas computacionales paraestudiar reacciones catalizadas en condiciones homogéneas, y más concretamentedescribimos a continuación estudios DFT de reacciones de ciclación catalizadaspor Paladio y Oro, así como algunos tipos de carbometalación.Capítulo 1. Se da un repaso introductorio de la catálisis organometálica ycatálisis en general usando una perspectiva histórica. Cubre los 9000 años de historiade la catálisis desde el 7000 a. C. (la más antigua evidencia de fermentación/ biocatálisis hecha por el hombre) a través de diversos hitos (Libavius, Berzelius,etc.) hasta la química organometálica de nuestros días.Capítulo 2. Es una breve descripción metodológica que intenta dar luz sobrelas formulaciones teóricas que se aplican en las herramientas químicas cuánticas,sin la intención de ser completa ni profusa, sino solamente arañando la superficiede esta parte tan compleja de la teoría.Los resultados de nuestros cálculos se presentan en tres capítulos separadosxiiiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla Fiser(capítulos 3, 4 y 5), en cada uno de los cuales se entremezclan con los resultadosexperimentales de nuestros colaboradores y otros grupos de investigación.Capítulo 3. Describe algunas características especiales de la química del paladio.En esta parte de la Tesis, se han estudiado reacciones de síntesis asimétricade QUINAP, mediante un acoplamiento C-P dinámico cinético asimétrico catalizadopor complejos de paladio (II). Además de QUINAP, se han estudiado otrosatropo-ligandos P, N por métodos DFT al nivel de cálculoM06/6-31+G(d,p)/SDD//B3LYP/6-31G(d)/LANL2DZ.Figure 0.0.1: Mecanismo Propuesto para la Epimerización de los IntermediosDiastereoméricos de Adición Oxidante (OAI y OAI¿).xivSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserLos resultados computacionales junto a las evidencias experimentales recopiladaspor nuestros colaboradores nos permiten proponer un mecanismo de reacciónbasado en la formación de intermedios catiónicos de adición oxidante, queen las condiciones de reacción sufren una interconversión rápida entre diferentesisómeros (Figura 0.0.1). La coordinación del nitrógeno de la isoquinolina al átomode Pd es esencial para facilitar el proceso.Los cálculos también muestran que se cumplen los requisitos energéticos parauna resolución cinética dinámica, ya que los intermedios de reacción equilibranrápidamente y evolucionan por estados de transición de transmetalación de barrerasde activación muy diferentes.xvSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserCapítulo 4. Se divide en dos partes en las que se estudian dos reacciones catalizadaspor Au(I) diferentes. En la primera sección, se ha estudiado computacionalmenteal detalle la reacción tándem de transposición / ciclación Nazarov catalizadaspor Au(I) de ésteres propargílicos, y nuestros cálculos revelan el mecanismodetallado en la Figura 0.0.2, permitiéndonos evaluar energéticamente la influenciade las estructuras de los substratos en la velocidad de reacción y en la regio- yestereoselectividad.Figure 0.0.2: Mecanismo de Reacción. Arriba: Transposición de Acetato enlos Inicios de la Reacción. Abajo: Paso de Ciclación desde el Complejo pre-Nazarov III y Protodesauración. Los Cambios en la Energía Libre de Gibbs(¿G) y Barreras de Activación (¿Gz) se dan en kcal/mol.xviSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserEn la segunda sección, se han calculado reacciones de cicloiosomerización catalizadaspor Au(I) (Figura 0.0.3). Los cálculos muestran que para ambos tipos desustratos mostrados, el paso de oxiauración ocurre con una barrera de activaciónmuy baja o inexistente cuando ocurre en la posición interna del triple enlace, resultandoen un proceso 5-exo-dig. La preferencia es puramente geométrica e independientedel tipo de sustitución, dando lugar tanto las ß-enaminonas como susequivalentes reducidos, ß-amino cetonas, de un modo robusto, apropiado y fiable.Figure 0.0.3: Estructuras de los Estados de Transición y sus CorrespondientesBarreras de Activación (¿Gz, se dan en kcal/mol) para los AlquinosTerminales e Internos.xviiSupervisor: Prof. Enrique Gómez Bengoa Author: Béla FiserCapítulo 5. Es un estudio sistemático de reacciones de ciclación catalizadaspor metales de transición. Se han estudiado sistemáticamente las ciclaciones conlos metales del grupo 10 por métodos computacionales, y basándonos en los resultados,se propone una extensión de las reglas clásicas de Baldwin para ciclacionesa la catálisis metálica (Figura 0.0.4)Figure 0.0.4: Metalaciones del Grupo 10 Estudiadas.Los resultados cualitativos han dado lugar a un resumen intuitivo de los resultadosque podría servir como guía para explorar nuevos procesos catalíticos decarbometalación.Los manuscritos publicados como resultado de estos capítulos se adjuntan enel Apéndice I.xvii
User Assisted Creation of Open-Linked Data for Training Web Information Extraction in a Social Network
No full textA parametric study of influence of material properties on car cabin environment
No full textRecently the author presented the paper describing a car cabin heat load model for the prediction of the car cabin environment. The model allowed to simulate a transient behavior of the car cabin, i.e. radiant temperature of surfaces, air temperature and relative humidity. The model was developed in Dymola and was built on the basic principles of thermodynamics and heat balance equations. The model was validated by experiments performed on the Škoda Felicia during various operational conditions. In this paper the authors present a parametric study investigating influence of material properties on a car cabin environment. The Matlab version of the car cabin heat load model has been developed and used. The model was extended by simple graphical user interface and it was deployed into the stand alone executable application. The aim of this parametric study is to identify most important material properties and its effect on the cabin environment during specific operational conditions of car. By means of a sensitive analysis it can identified which material parameters have to be defined precisely and which parameters are not so important for the prediction of the air temperature inside cabin
