Circle-based Eye Center Localization (CECL)

We propose an improved eye center localization method based on the Hough transform, called Circle-based Eye Center Localization (CECL) that is simple, robust, and achieves accuracy on a par with typically more complex state-of-the-art methods. The CECL method relies on color and shape cues that distinguish the iris from other facial structures. The accuracy of the CECL method is demonstrated through a comparison with 15 state-of-the-art eye center localization methods against five error thresholds, as reported in the literature. The CECL method achieved an accuracy of 80.8% to 99.4% and ranked first for 2 of the 5 thresholds. It is concluded that the CECL method offers an attractive alternative to existing methods for automatic eye center localization.Comment: Published and presented at The 14th IAPR International Conference on Machine Vision Applications, 2015. http://www.mva-org.jp/mva2015

Modeling Regional Variation of Cortical Spreading Depression: A Computational Study

University of Minnesota Ph.D. dissertation. May 2019. Major: Mathematics. Advisor: Yoichiro Mori. 1 computer file (PDF); vii, 126 pages.Cortical Spreading Depression(CSD) is a pathological phenomenon in the central nervous system in which normal cellular function is disrupted by a prolonged depolarization due to massive ionic fluxes. This spreads at a rate of millimeters per minute and is connected to with several medical conditions: migraine aura, stroke, traumatic brain injury, etc. In this thesis we present a multi-phasic continuum electrodiffusion model of spreading depression. The main result of this work is the efficient numerical simulation of 2D and 3D versions of this model. We make use of these simulations by focusing on the introduction of NMDA receptors and their effects on previous findings. From there, we investigate spatial variance of CSD in two ways. First, the natural occurrence of spiral wave patterns in a homogeneous domain. Second, we introduce spatial dependence of parameters to investigate how the varied structure of the hippocampus can impact CSD

2019 Oklahoma Research Day Full Program

Oklahoma Research Day 2019 - SWOSU Celebrating 20 years of Undergraduate Research Successes

From Vision-Language Multimodal Learning Towards Embodied Agents

To build machine agents with intelligent capabilities mimicking human perception and cognition, vision and language stand out as two essential modalities and foster computer vision and natural language processing. Advances in such realms stimulate research in vision-language multimodal learning that allows optical and linguistic inputs and outputs. Due to the innate difference between the two modalities and the lack of large-scale fine-grained annotations, multimodal agents tend to inherit unimodal shortcuts. In this thesis, we develop various solutions to intervene unimodal shortcuts for multimodal generation and reasoning. For visual shortcuts, we introduce a linguistic prior and devise a syntax-aware action targeting module for dynamic description to rectify the correlation between subject and object in a sentence. We apply concept hierarchy and propose a visual superordinate abstraction framework for unbiased concept learning to reduce the correlation among different attributes of an object. For linguistic shortcuts, we disentangle the topic and syntax to reduce the repetition in generated paragraph descriptions for a given image. With the ubiquity of large-scale pre-trained models, we leverage self-supervised learning in finetuning process to increase the robustness of multimodal reasoning. The rapid development in multimodal learning promises embodied agents capable of interacting with physical environments. This thesis studies the typical embodied task vision-and-language navigation in discrete scenarios and proposes an episodic scene memory (ESceme) mechanism to balance generalization and efficiency. We figure out one desirable instantiation of the mechanism, namely candidate enhancing, and validate its superiority in various settings. Without extra time and computational cost before inference, ESceme improves performance in unseen environments by a large margin. We hope our findings can inspire more practical explorations on episodic memory in embodied AI

Sistemi basati su ossidi metallici per l'efficiente conversione di luce visibile

Oggigiorno la ricerca nel campo delle fonti di energia rinnovabile è fondamentale per arginare la crisi climatica e superare la riduzione della disponibilità di combustibili fossili. Grazie all'elevata intensità dell'energia solare, molte ricerche si concentrano su metodi efficienti per convertirla in altre forme di energia (ad esempio, elettrica o chimica). Uno dei metodi più promettenti per convertire l'energia solare in energia chimica è la fotocatalisi a luce visibile. L'obiettivo principale di questa tesi è lo studio di sistemi su scala nanometrica che siano candidati promettenti per la fotocatalisi di luce visibile, ed in particolare di film sottili di ossido di rame e di ossido di cerio combinati con nanoparticelle (NPs) plasmoniche. Nel secondo caso, l'ossido di cerio è stato accoppiato con le NPs dal momento che l’energia di gap dell'ossido nudo è troppo ampia per l’assorbimento della radiazione visibile; mentre lavori precedenti hanno dimostrato che la formazione di un’eterogiunzione, ottenuta accoppiando nanostrutture plasmoniche con semiconduttori, può aumentare notevolmente l'attività di fotocatalizzatori mediante trasferimento di energia plasmonica dalla nanostruttura metallica al semiconduttore. La prima parte della tesi descriverà la crescita e la caratterizzazione di questi sistemi, volti ad estrarre informazioni sulle loro proprietà ottiche, con un focus specifico sulla dinamica ultraveloce e sull'evoluzione temporale degli stati eccitati. A tale scopo, sono stati studiati sistemi composti da Ag, Au e Cu NPs circondati da CeO2 mediante analisi di assorbanza ed emissione statiche e risolte nel tempo. In primo luogo, sono stati studiati sistemi composti da Ag NP con CeO2 con spettroscopia di fotoemissione risolta in tempo e spettroscopia di assorbimento a raggi X risolta in tempo con laser a elettroni liberi. In secondo luogo, la dinamica ultraveloce degli stati eccitati indotti dall'eccitazione della luce ultravioletta e visibile è stata esplorata in sistemi composti da Au NPs combinate con ossido di cerio, volti a comprendere i meccanismi di eccitazione, utilizzando la spettroscopia di assorbimento transitorio ultraveloce. Infine, l'ultima parte della tesi è focalizzata sulle Cu NPs, anch'esse incorporate in film di CeO2, o circondate da ossidi, in particolare Cu2O, che, grazie al suo band gap nella regione del visibile, è un candidato promettente per la catalisi della luce solare. Le Cu NPs sono state studiate in termini di morfologia, proprietà ottiche e stabilità in condizioni atmosferiche ed è stata sviluppata e studiata una procedura per la crescita di NPs con core metallico e shell di Cu2O. Infine, cristalli e film di Cu2O di diverso spessore sono stati cresciuti e analizzati mediante diffrazione elettronica a bassa energia, microscopia a effetto tunnel e spettroscopia di fotoluminescenza in un ampio intervallo di temperature per ottenere informazioni sul comportamento degli eccitoni.Nowadays, the research in the field of renewable energy sources is fundamental, to stem the climate crisis and to overcome the reducing availability of fossil fuels. Thanks to the high magnitude of solar energy a lot of research is focused on efficient methods to convert it into other energy forms (e.g. electric or chemical). One of the most promising methods to convert solar into chemical energy is visible light photocatalysis. The main aim of this thesis is the investigations of systems at the nanoscale that are promising candidates for visible light photocatalysis, and in particular of thin films of cuprous oxide and of cerium oxide combined with plasmonic nanoparticles (NPs). In the latter, cerium oxide has been coupled with NPs because the band gap of the bare oxide is too wide for the absorption of visible radiation, but previous works demonstrated that the formation of heterojunctions by coupling plasmonic nanostructures with semiconductors can greatly enhance the activity of photocatalysts by plasmonic energy transfer from the metal nanostructure to the semiconductor. The first part of the thesis will describe the growth and characterization of these systems, aimed to extract information on their optical properties, with a specific focus on the ultrafast dynamics and temporal evolution of excited states. For this purpose, systems composed by Ag, Au and Cu NPs surrounded by CeO2 have been investigated by means of time-resolved and static absorbance and emission analysis. First, systems composed by Ag NPs with CeO2 have been studied with time-resolved photoemission spectroscopy and free electron laser time-resolved X-ray absorption spectroscopy. Secondly, the ultrafast dynamics of excited states induced by ultra-violet and visible light excitation has been explored in Au NPs combined with cerium oxide, aimed at understanding the excitation pathways, using femtosecond transient absorption spectroscopy. Finally, the last part of the thesis is focused on Cu NPs, also embedded in CeO2 films, or surrounded by oxides, in particular on Cu2O, that, thanks to its band gap in the visible region, is a promising candidate for solar light catalysis. Cu NPs have been investigated in terms of their morphology, optical properties, and stability in air conditions, and a procedure for growing metallic core-Cu2O shell has been developed and investigated. Finally, Cu2O crystals and films of different thickness have been grown and analyzed by means of low energy electron diffraction, scanning tunneling microscopy and photoluminescence spectroscopy in a wide temperature range to obtain information on the behavior of excitons

Circle-based Eye Center Localization (CECL)

The ability to automatically detect eye center locations in video images allows for estimating gaze direction. This, in turn, facilitates the study of human-computer interaction and behavioral analyses of social interactions. We propose an improved eye center localization method based on the Hough transform, called Circle-based Eye Center Localization (CECL) that is simple, robust, and achieves accuracy at a par with typically more complex state-of-the-art methods. The CECL method relies on color and shape cues that distinguish the iris from other facial structures. The circle enclosing the iris is localized by means of the Hough transform and the center of the iris is determined using the intensity level within the detected circle. The accuracy of the CECL method is demonstrated through a comparison with 15 state-of-the-art eye center localization methods against five error thresholds, as reported in the literature. The CECL method achieved an accuracy of 80.8% to 99.4% and ranked first for 2 of the 5 thresholds. It is concluded that the CECL method offers an attractive alternative to existing methods for automatic eye center localization